Earth Sciences,News & Press - A Blog by F.Intilla (WWW.OLOSCIENCE.COM)

Here’s a rapid solution to find out how solar panels work.

2010-06-17T00:50:00.000-07:00

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What exactly is solar energy ?
Solar energy is radiant energy which is produced by the sun. Every day the sun radiates, or sends out, an enormous volume of energy. The sun radiates more energy in a single second than people have used since the beginning of time!
The energy of the Sun comes from within the sun itself. Like other stars, the sun is really a big ball of gases––mostly hydrogen and helium atoms.
The hydrogen atoms in the sun’s core combine to form helium and generate energy in a process called nuclear fusion.

During nuclear fusion, the sun’s extremely high pressure and temperature cause hydrogen atoms to come apart and their nuclei (the central cores of the atoms) to fuse or combine. Four hydrogen nuclei fuse to become one helium atom. However the helium atom contains less mass compared to four hydrogen atoms that fused. Some matter is lost during nuclear fusion. The lost matter is emitted into space as radiant energy.
It takes millions of years for the energy in the sun’s core to make its way to the solar surface, and somewhat over eight minutes to travel the 93 million miles to earth. The solar energy travels to the earth at a speed of 186,000 miles per second, the speed of light.
Only a small part of the energy radiated from the sun into space strikes the earth, one part in two billion. Yet this volume of energy is enormous. On a daily basis enough energy strikes the united states to supply the nation’s energy needs for one and a half years!

Where does all this energy go?

About 15 percent of the sun’s energy that hits our planet is reflected back into space. Another 30 percent is used to evaporate water, which, lifted in to the atmosphere, produces rainfall. Solar power is also absorbed by plants, the land, and the oceans. The remaining could be used to supply our energy needs.
Who invented solar technology ?
Humans have harnessed solar energy for hundreds of years. As early as the 7th century B.C., people used simple magnifying glasses to concentrate the light of the sun into beams so hot they would cause wood to catch fire. Over a century ago in France, a scientist used heat from a solar collector to create steam to drive a steam engine. In the beginning of this century, scientists and engineers began researching ways to use solar technology in earnest. One important development was a remarkably efficient solar boiler invented by Charles Greeley Abbott, an american astrophysicist, in 1936.

The solar water heater gained popularity at this time in Florida, California, and the Southwest. The industry started in the early 1920s and was in full swing just before World War II. This growth lasted before mid-1950s when low-cost natural gas had become the primary fuel for heating American homes.
People and world governments remained largely indifferent to the possibilities of solar technology until the oil shortages of the1970s. Today, people use solar technology to heat buildings and water and also to generate electricity.
How we use solar power today ?
Solar energy is employed in a variety of ways, of course. There are 2 standard forms of solar power:

* Solar thermal energy collects the sun's warmth through 1 of 2 means: in water or in an anti-freeze (glycol) mixture.

* Solar photovoltaic energy converts the sun's radiation to usable electricity.

Listed below are the five most practical and popular ways that solar energy is used:

1. Small portable solar photovoltaic systems. We see these used everywhere, from calculators to solar garden tools. Portable units can be utilized for everything from RV appliances while single panel systems are used for traffic signs and remote monitoring stations.

2. Solar pool heating. Running water in direct circulation systems via a solar collector is an extremely practical solution to heat water for your pool or hot spa.

3. Thermal glycol energy to heat water. In this method (indirect circulation), glycol is heated by sunshine and the heat is then transferred to water in a hot water tank. This process of collecting the sun's energy is more practical now than ever before. In areas as far north as Edmonton, Alberta, solar thermal to heat water is economically sound. It can pay for itself in three years or less.

4. Integrating solar photovoltaic energy into your home or office power. In most parts on the planet, solar photovoltaics is an economically feasible approach to supplement the power of your home. In Japan, photovoltaics are competitive with other forms of power. In the USA, new incentive programs make this form of solar technology ever more viable in many states. An increasingly popular and practical way of integrating solar energy into the power of your home or business is through the use of building integrated solar photovoltaics.

5. Large independent photovoltaic systems. For those who have enough sun power at your site, you could possibly go off grid. It's also possible to integrate or hybridize your solar energy system with wind power or other forms of renewable energy to stay 'off the grid.'

How can Photovoltaic panels work ?
Silicon is mounted beneath non-reflective glass to create photovoltaic panels. These panels collect photons from the sun, converting them into DC electrical energy. The energy created then flows into an inverter. The inverter transforms the power into basic voltage and AC electrical power.
Photovoltaic cells are prepared with particular materials called semiconductors for example silicon, which is presently the most generally used. When light hits the Photovoltaic cell, a certain share of it is absorbed inside the semiconductor material. This means that the energy of the absorbed light is given to the semiconductor.

The power unfastens the electrons, permitting them to run freely. Photovoltaic cells also have one or more electric fields that act to compel electrons unfastened by light absorption to flow in a specific direction. This flow of electrons is a current, and by introducing metal links on the top and bottom of the -Photovoltaic cell, the current can be drawn to use it externally.
What are the benefits and drawbacks of solar power ?

Solar Pro Arguments:

- Heating our homes with oil or natural gas or using electricity from power plants running with coal and oil is a reason for climate change and climate disruption. Solar power, on the other hand, is clean and environmentally-friendly.

- Solar hot-water heaters require little maintenance, and their initial investment could be recovered within a relatively limited time.

- Solar hot-water heaters can work in almost any climate, even just in very cold ones. You just need to choose the right system for your climate: drainback, thermosyphon, batch-ICS, etc.

- Maintenance costs of solar powered systems are minimal and also the warranties large.

- Financial incentives (USA, Canada, European states…) can reduce the price of the first investment in solar technologies. The U.S. government, for example, offers tax credits for solar systems certified by by the SRCC (Solar Rating and Certification Corporation), which amount to 30 percent of the investment (2009-2016 period).

Solar Cons Arguments:

- The initial investment in Solar Hot water heaters or in Solar PV Electric Systems is greater than that required by conventional electric and gas heaters systems.

- The payback period of solar PV-electric systems is high, as well as those of solar space heating or solar cooling (only the solar warm water heating payback is short or relatively short).

- Solar water heating do not support a direct in conjunction with radiators (including baseboard ones).

- Some air cooling (solar space heating and the solar cooling systems) are costly, and rather untested technologies: solar air conditioning isn't, till now, a really economical option.

- The efficiency of solar powered systems is rather influenced by sunlight resources. It's in colder climates, where heating or electricity needs are higher, that the efficiency is smaller.

About me - Barbara Young writes on motorhome solar power in her personal hobby blog 12voltsolarpanels.net. Her work is centered on helping people save energy using solar power to reduce CO2 emissions and energy dependency.

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2010-01-11T13:36:00.001-08:00

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Google Earth Application Maps Carbon's Course.

2009-10-01T11:15:00.001-07:00

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ScienceDaily (Sep. 30, 2009) — Sometimes a picture really is worth a thousand words, particularly when the picture is used to illustrate science. Technology is giving us better pictures every day, and one of them is helping a NASA-funded scientist and her team to explain the behavior of a greenhouse gas.

Google Earth -- the digital globe on which computer users can fly around the planet and zoom in on key features -- is attracting attention in scientific communities and aiding public communication about carbon dioxide. Recently Google held a contest to present scientific results using KML, a data format used by Google Earth.
"I tried to think of a complex data set that would have public relevance," said Tyler Erickson, a geospatial researcher at the Michigan Tech Research Institute in Ann Arbor.
He chose to work with data from NASA-funded researcher Anna Michalak of the University of Michigan, Ann Arbor, who develops complex computer models to trace carbon dioxide back in time to where it enters and leaves the atmosphere.
"The datasets have three spatial dimensions and a temporal dimension," Erickson said. "Because the data is constantly changing in time makes it particularly difficult to visualize and analyze."
A better understanding of the carbon cycle has implications for energy and environmental policy and carbon management. In June 2009, Michalak described this research at the NASA Earth System Science at 20 symposium in Washington, D.C.
A snapshot from Erickson's Google Earth application shows green tracks representing carbon dioxide in the lowest part of the atmosphere close to Earth's surface where vegetation and land processes can impact the carbon cycle. Red tracks indicate particles at higher altitudes that are immune from ground influences.
The application is designed to educate the public and even scientists about how carbon dioxide emissions can be traced. A network of 1,000-foot towers across the United States is equipped with instruments by NOAA to measure the carbon dioxide content of parcels of air at single locations.
The application is designed to educate the public and even scientists about how carbon dioxide emissions can be traced. A network of 1,000-foot towers across the United States, like the tower above, are equipped with instruments by NOAA to measure the carbon dioxide content of parcels of air at single locations.
But where did that gas come from and how did it change along its journey? To find out, scientists rely on a sleuthing technique called "inverse modeling" – measuring gas concentrations at a single geographic point and then using clues from weather and atmospheric models to deduce where it came from. The technique is complex and difficult to explain even to fellow scientists.
Michalak related the technique to cream in a cup of coffee. "Say someone gave you a cup of creamy coffee," Michalak said. "How do you know when that cream was added?" Just as cream is not necessarily mixed perfectly, neither is the carbon dioxide in the atmosphere. If you can see the streaks of cream (carbon dioxide) and understand how the coffee (atmosphere) was stirred (weather), then scientists can use those clues to retrace the time and location that the ingredient was added to the mix.
The visual result typically used by scientists is a static two-dimensional map of the location of the gas, as averaged over the course of a month. Most carbon scientists know how to interpret the 2D map, but visualizing the 3D changes for non-specialists has proved elusive. Erickson spent 70 hours programming the Google Earth application that makes it easy to navigate though time and watch gas particles snake their way toward the NOAA observation towers. For his work, Erickson was declared one of Google's winners in March 2009.
"Having this visual tool allows us to better explain the scientific process," Michalak said. "It's a much more human way of looking at the science."
The next step, Erickson said, is to adapt the application to fit the needs of the research community. Scientists could use the program to better visualize the output of complex atmospheric models and then improve those models so that they better represent reality.
"Encouraging more people to deliver data in an interactive format is a good trend," Erickson said. "It should help innovation in research by reducing barriers to sharing data."
Adapted from materials provided by NASA.

San Andreas Affected By 2004 Sumatran Quake; Largest Quakes Can Weaken Fault Zones Worldwide.

2009-10-01T11:01:00.001-07:00

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ScienceDaily (Sep. 30, 2009) — U.S. seismologists have found evidence that the massive 2004 earthquake that triggered killer tsunamis throughout the Indian Ocean weakened at least a portion of California's famed San Andreas Fault. The results, which appear this week in the journal Nature, suggest that the Earth's largest earthquakes can weaken fault zones worldwide and may trigger periods of increased global seismic activity.

"An unusually high number of magnitude 8 earthquakes occurred worldwide in 2005 and 2006," said study co-author Fenglin Niu, associate professor of Earth science at Rice University. "There has been speculation that these were somehow triggered by the Sumatran-Andaman earthquake that occurred on Dec. 26, 2004, but this is the first direct evidence that the quake could change fault strength of a fault remotely."
Earthquakes are caused when a fault fails, either because of the buildup of stress or because of the weakening of the fault. The latter is more difficult to measure.
The magnitude 9 earthquake in 2004 occurred beneath the ocean west of Sumatra and was the second-largest quake ever measured by seismograph. The temblor spawned tsunamis as large as 100 feet that killed an estimated 230,000, mostly in Indonesia, Sri Lanka, India and Thailand.
In the new study, Niu and co-authors Taka'aki Taira and Paul Silver, both of the Carnegie Institution of Science in Washington, D.C., and Robert Nadeau of the University of California, Berkeley, examined more than 20 years of seismic records from Parkfield, Calif., which sits astride the San Andreas Fault.
The team zeroed in on a set of repeating microearthquakes that occurred near Parkfield over two decades. Each of these tiny quakes originated in almost exactly the same location. By closely comparing seismic readings from these quakes, the team was able to determine the "fault strength" -- the shear stress level required to cause the fault to slip -- at Parkfield between 1987 and 2008.
The team found fault strength changed markedly at three times during the 20-year period. The authors surmised that the 1992 Landers earthquake, a magnitude 7 quake north of Palm Springs, Calif. -- about 200 miles from Parkfield -- caused the first of these changes. The study found the Landers quake destabilized the fault near Parkfield, causing a series of magnitude 4 quakes and a notable "aseismic" event -- a movement of the fault that played out over several months -- in 1993.
The second change in fault strength occurred in conjunction with a magnitude 6 earthquake at Parkfield in September 2004. The team found another change at Parkfield later that year that could not be accounted for by the September quake alone. Eventually, they were able to narrow the onset of this third shift to a five-day window in late December during which the Sumatran quake occurred.
"The long-range influence of the 2004 Sumatran-Andaman earthquake on this patch of the San Andreas suggests that the quake may have affected other faults, bringing a significant fraction of them closer to failure," said Taira. "This hypothesis appears to be borne out by the unusually high number of large earthquakes that occurred in the three years after the Sumatran-Andaman quake."
The research was supported by the National Science Foundation, the Carnegie Institution of Washington, the University of California, Berkeley, and the U.S. Geological Survey.
Adapted from materials provided by Rice University.

Auroras In Northern And Southern Hemispheres Are Not Identical

2009-07-25T00:54:00.000-07:00

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ScienceDaily (July 24, 2009) — Norwegian researchers have shown that the auroras in the Northern and the Southern hemispheres can be totally asymmetric. These findings contradict the commonly made assumption of aurora being mirror images of each other.

The study was performed by PhD student Karl Magnus Laundal and professor Nikolai Østgaard at the Institute of Physics and Technology at the University of Bergen.
"The aurora is produced due to collisions between the Earth’s atmosphere and electrically charged particles streaming along the Earth’s geomagnetic field lines. – Since these processes occur above the two hemispheres, both the Northern and the Southern light are created. So far researchers have assumed that these auroras are mirror images of each other, but our findings show that this is not always the case," professor Nikolai Østgaard says.
The researchers at the University of Bergen have used data from the two NASA-satellites IMAGE and Polar to examine the Northern and the Southern light. In the Nature letter they present several possible explanations to the unexpected result.
"The most plausible explanation involves electrical currents along the magnetic field lines. Differences in the solar exposure may lead to currents between the two hemispheres, explaining why the Northern and the Southern light are not identical," PhD student Karl Magnus Laundal says.
In addition to yielding new knowledge about the aurora, the results are important for other researchers studying the near-Earth space.
"Our study shows that data from only one hemisphere is not sufficient to state the conditions on the other hemisphere. This is important because most of our knowledge about the aurora, as well as processes in the upper atmosphere in the polar regions, is based solely on data from the Northern hemisphere," Østgaard points out.
The work of Østgaard and Laundal has been financed by the Research Council of Norway via the International Polar Year project IPY-ICESTAR.
Laundal, K.M. and Østgaard, N., Asymmetric auroral intensities in the Earth's Northern and Southern hemispheres, Nature 460, 491-493 (23 July 2009) doi:10.1038/nature08154
Journal reference:
Laundal et al. Asymmetric auroral intensities in the Earth's Northern and Southern hemispheres. Nature, 2009; 460 (7254): 491 DOI: 10.1038/nature08154
Adapted from materials provided by University of Bergen, via AlphaGalileo.

California's Channel Islands Hold Evidence Of Clovis-age Comets

2009-07-22T08:20:00.001-07:00

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ScienceDaily (July 21, 2009) — A 17-member team has found what may be the smoking gun of a much-debated proposal that a cosmic impact about 12,900 years ago ripped through North America and drove multiple species into extinction.

In a paper appearing online ahead of regular publication in the Proceedings of the National Academy of Sciences, University of Oregon archaeologist Douglas J. Kennett and colleagues from nine institutions and three private research companies report the presence of shock-synthesized hexagonal diamonds in 12,900-year-old sediments on the Northern Channel Islands off the southern California coast.
These tiny diamonds and diamond clusters were buried deeply below four meters of sediment. They date to the end of Clovis -- a Paleoindian culture long thought to be North America's first human inhabitants. The nano-sized diamonds were pulled from Arlington Canyon on the island of Santa Rosa that had once been joined with three other Northern Channel Islands in a landmass known as Santarosae.
The diamonds were found in association with soot, which forms in extremely hot fires, and they suggest associated regional wildfires, based on nearby environmental records.
Such soot and diamonds are rare in the geological record. They were found in sediment dating to massive asteroid impacts 65 million years ago in a layer widely known as the K-T Boundary. The thin layer of iridium-and-quartz-rich sediment dates to the transition of the Cretaceous and Tertiary periods, which mark the end of the Mesozoic Era and the beginning of the Cenozoic Era.
"The type of diamond we have found -- Lonsdaleite -- is a shock-synthesized mineral defined by its hexagonal crystalline structure. It forms under very high temperatures and pressures consistent with a cosmic impact," Kennett said. "These diamonds have only been found thus far in meteorites and impact craters on Earth and appear to be the strongest indicator yet of a significant cosmic impact [during Clovis]."
The age of this event also matches the extinction of the pygmy mammoth on the Northern Channel Islands, as well as numerous other North American mammals, including the horse, which Europeans later reintroduced. In all, an estimated 35 mammal and 19 bird genera became extinct near the end of the Pleistocene with some of them occurring very close in time to the proposed cosmic impact, first reported in October 2007 in PNAS.
In the Jan. 2, 2009, issue of the journal Science, a team led by Kennett reported the discovery of billions of nanometer-sized diamonds concentrated in sediments -- weighing from about 10 to 2,700 parts per billion -- in six North American locations.
"This site, this layer with hexagonal diamonds, is also associated with other types of diamonds and with dramatic environmental changes and wildfires," said James Kennett, paleoceanographer and professor emeritus in the Department of Earth Science at the University of California, Santa Barbara.
"There was a major event 12,900 years ago," he said. "It is hard to explain this assemblage of materials without a cosmic impact event and associated extensive wildfires. This hypothesis fits with the abrupt cooling of the atmosphere as shown in the record of ocean drilling of the Santa Barbara Channel. The cooling resulted when dust from the high-pressure, high-temperature, multiple impacts was lofted into the atmosphere, causing a dramatic drop in solar radiation."
The hexagonal diamonds from Arlington Canyon were analyzed at the UO's Lorry I. Lokey Laboratories, a world-class nanotechnology facility built deep in bedrock to allow for sensitive microscopy and other high-tech analyses of materials. The analyses were done in collaboration with FEI, a Hillsboro, Ore., company that distributes the high-resolution Titan microscope used to characterize the hexagonal diamonds in this study.
Transmission electron microscopy and scanning electron microscopes were used in the extensive analyses of the sediment that contained clusters of Lonsdaleite ranging in size from 20 to 1,800 nanometers. These diamonds were inside or attached to carbon particles found in the sediments.
These findings are inconsistent with the alternative and already hotly debated theory that overhunting by Clovis people led to the rapid extinction of large mammals at the end of the ice age, the research team argues in the PNAS paper. An alternative theory has held that climate change was to blame for these mass extinctions. The cosmic-event theory suggests that rapid climate change at this time was possibly triggered by a series of small and widely dispersed comet strikes across much of North America.
The National Science Foundation provided primary funding for the research. Additional funding was provided by way of Richard A. Bray and Philip H. Knight faculty fellowships of the University of Oregon, respectively, to Kennett and UO colleague Jon M. Erlandson, a co-author and director of the UO's Museum of Natural and Cultural History.
The 17 co-authors on the PNAS paper are Douglas Kennett, Erlandson and Brendan J. Culleton, all of the University of Oregon; James P. Kennett of UC Santa Barbara; Allen West of GeoScience Consulting in Arizona; G. James West of the University of California, Davis; Ted E. Bunch and James H. Wittke, both of Northern Arizona University; Shane S. Que Hee of the University of California, Los Angeles; John R. Johnson of the Santa Barbara Museum of Natural History; Chris Mercer of the Santa Barbara Museum of Natural History and National Institute of Materials Science in Japan; Feng Shen of the FEI Co.; Thomas W. Stafford of Stafford Research Inc. of Colorado; Adrienne Stich and Wendy S. Wolbach, both of DePaul University in Chicago; and James C. Weaver of the University of California, Riverside.
About the University of Oregon
The University of Oregon is a world-class teaching and research institution and Oregon's flagship public university. The UO is a member of the Association of American Universities (AAU), an organization made up of the 62 leading public and private research institutions in the United States and Canada. The UO is one of only two AAU members in the Pacific Northwest.
Alternate Media Contact: Gail Gallessich, science writer, UC Santa Barbara, 805-893-7220, .edu
Sources: Douglas Kennett, professor of archaeology, department of anthropology, .edu. He currently is in Europe and readily assessable by email (a phone number is available through the UO media contact above)
James Kennett, professor emeritus, UC Santa Barbara, 805-893-4187, .edu (home phone number for media access is available from either media contact above)
Links: Doug Kennett faculty page: http://www.uoregon.edu/~dkennett/Welcome.html; anthropology department: http://www.uoregon.edu/~anthro/
James Kennett faculty page: http://www.geol.ucsb.edu/faculty/kennett/Home.html
Adapted from materials provided by University of Oregon.

First Remote, Underwater Detection Of Harmful Algae, Toxins

2009-07-15T22:59:00.001-07:00

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ScienceDaily (July 15, 2009) — Scientists at NOAA's National Centers for Coastal Ocean Science and the Monterey Bay Aquarium Research Institute (MBARI) have successfully conducted the first remote detection of a harmful algal species and its toxin below the ocean's surface. The achievement was recently reported in the June issue of Oceanography.

This achievement represents a significant milestone in NOAA's effort to monitor the type and toxicity of harmful algal blooms (HABs). HABs are considered to be increasing not only in their global distribution, but also in the frequency, duration, and severity of their effects. HABs damage coastal ecosystem health and pose threats to humans as well as marine life. Climate change is expected to exacerbate this trend, since many critical processes that govern HABs dynamics, such as water temperature and ocean circulation, are influenced by climate.
A MBARI-designed robotic instrument called the Environmental Sample Processor, or 'ESP,' designed as a fully-functional analytical laboratory in the sea, lets researchers collect the algal cells and extract the genetic information required for organism identification as well as the toxin needed to assess the risk to humans and wildlife. The ESP then conducts specialized, molecular-based measurements of species and toxin abundance, and transmits results to the laboratory via radio signals.
"This represents the first autonomous detection of both a HAB species and its toxin by an underwater sensor," notes Greg Doucette, Ph.D., a research oceanographer at NOAA's Center for Coastal Environmental Health and Biomolecular Research laboratory in Charleston, S.C. "It allows us to determine not only the organism causing a bloom, but also the toxicity of the event, which ultimately dictates whether it is a threat to the public and the ecosystem."
For the first demonstration of the ESP's ability to detect HABs and their toxins, Doucette and his MBARI colleague, Chris Scholin, Ph.D., targeted certain members of the algal genus Pseudo-nitzschia and their neurotoxin, domoic acid in Monterey Bay, Calif.
Pseudo-nitzschia and domoic acid have been a concern in the Monterey Bay area for well over a decade. In 1991, the first U.S. outbreak of domoic acid poisoning was documented in Monterey Bay. This outbreak resulted in the unusual deaths of numerous pelicans and cormorants that ingested sardines and anchovies, which had accumulated the domoic acid by feeding on a bloom of the toxic algae.
In the spring of 1998, a mass mortality of sea lions in and around the Monterey Bay area was attributed to the sea lions' feeding on domoic acid contaminated anchovies. Since that time, Pseudo-nitzschia and domoic acid have appeared on virtually an annual basis in California coastal waters and are the objects of an intensive statewide monitoring program run by the California Dept. of Public Health. Humans also can be affected by the toxin through consumption of contaminated seafood such as shellfish.
"Our public health monitoring program is one of the many groups that can benefit directly from the ESP technology and ability to provide an early warning of impending bloom activity and toxicity," said Gregg Langlois, director of the state of California's Marine Biotoxin Monitoring Program. "This is critical information for coastal managers and public health officials in mitigating impacts on the coastal ecosystem, since the toxicity of these algae can vary widely from little or no toxicity to highly toxic."
Beyond improving forecasting of HABs, this research will contribute to the rapidly emerging U.S. Integrated Ocean Observing System (IOOS) by adding a new way to make coastal ocean observations.
Adapted from materials provided by National Oceanic and Atmospheric Administration.

Tremors On Southern San Andreas Fault May Mean Increased Earthquake Risk

2009-07-13T04:05:00.001-07:00

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ScienceDaily (July 13, 2009) — Increases in mysterious underground tremors observed in several active earthquake fault zones around the world could signal a build-up of stress at locked segments of the faults and presumably an increased likelihood of a major quake, according to a new University of California, Berkeley, study.

Seismologist Robert M. Nadeau and graduate student Aurélie Guilhem of UC Berkeley draw these conclusions from a study of tremors along a heavily instrumented segment of the San Andreas Fault near Parkfield, Calif. The research is reported in the July 10 issue of Science.
They found that after the 6.5-magnitude San Simeon quake in 2003 and the 6.0-magnitude Parkfield quake in 2004, underground stress increased at the end of a locked segment of the San Andreas Fault near Cholame, Calif., at the same time as tremors became more frequent. The tremors have continued to this day at a rate significantly higher than the rate before the two quakes.
The researchers conclude that the increased rate of tremors may indicate that stress is accumulating more rapidly than in the past along this segment of the San Andreas Fault, which is at risk of breaking like it did in 1857 to produce the great 7.8 magnitude Fort Tejon earthquake. Strong quakes have also occurred just to the northwest along the Parkfield segment of the San Andreas about every 20 to 30 years.
"We've shown that earthquakes can stimulate tremors next to a locked zone, but we don't yet have evidence that this tells us anything about future quakes," Nadeau said. "But if earthquakes trigger tremors, the pressure that stimulates tremors may also stimulate earthquakes."
While earthquakes are brief events originating, typically, no deeper than 15 kilometers (10 miles) underground in California, tremors are an ongoing, low-level rumbling from perhaps 15 to 30 kilometers (10-20 miles) below the surface. They are common near volcanoes as a result of underground fluid movement, but were a surprise when discovered in 2002 at a subduction zone in Japan, a region where a piece of ocean floor is sliding under a continent.
Tremors were subsequently detected at the Cascadia subduction zone in Washington, Oregon and British Columbia, where several Pacific Ocean plates dive under the North American continental plate. In 2005, Nadeau identified mysterious "noise" detected by the Parkfield borehole seismometers as tremor activity, and has focused on them ever since. Unlike the Japanese and Cascadia tremor sites, however, the Parkfield area is a strike/slip fault, where the Pacific plate is moving horizontally against the North American plate.
"The Parkfield tremors are smaller versions of the Cascadia and Japanese tremors," Nadeau said. "Most last between three and 21 minutes, while some Cascadia tremors go on for days."
Because in nearly all known instances the tremors originate from the edge of a locked zone - a segment of a fault that hasn't moved in years and is at high risk of a major earthquake - seismologists have thought that increases in their activity may forewarn of stress build-up just before an earthquake.
The new report strengthens that association, Nadeau said.
For the new study, Nadeau and Guilhem pinpointed the location of nearly 2,200 tremors recorded between 2001 and 2009 by borehole seismometers implanted along the San Andreas Fault as part of UC Berkeley's High-Resolution Seismic Network. During this period, two nearby earthquakes occurred: one in San Simeon, 60 kilometers from Parkfield, on Dec. 22, 2003, and one in Parkfield on the San Andreas Fault on Sept. 28, 2004.
Before the San Simeon quake, tremor activity was low beneath the Parkfield and Cholame segments of the San Andreas Fault, but it doubled in frequency afterward and was six times more frequent after the Parkfield quake. Most of the activity occurred along a 25-kilometer (16-mile) segment of the San Andreas Fault south of Parkfield, around the town of Cholame. Fewer than 10 percent of the tremors occurred at an equal distance above Parkfield, near Monarch Peak. While Cholame is at the northern end of a long-locked and hazardous segment of the San Andreas Fault, Monarch Peak is not. However, Nadeau noted, Monarch Peak is an area of relative complexity on the San Andreas Fault and also ruptured in 1857 in the Fort Tejon 7.8 earthquake.
The tremor activity remains about twice as high today as before the San Simeon quake, while periodic peaks of activity have emerged that started to repeat about every 50 days and are now repeating about every 100-110 days.
"What's surprising is that the activity has not gone down to its old level," Nadeau said. The continued activity is worrisome because of the history of major quakes along this segment of the fault, and the long-ago Fort Tejon quake, which ruptured southward from Monarch Peak along 350 kilometers (220 miles) of the San Andreas Fault.
A flurry of pre-tremors was detected a few days before the Parkfield quake, which makes Nadeau hopeful of seeing similar tremors preceding future quakes.
He noted that the source of tremors is still somewhat of a mystery. Some scientists think fluids moving underground generate the tremors, just as movement of underground magma, water and gas causes volcanic tremors. Nadeau leans more toward an alternative theory, that non-volcanic tremors are generated in a deep region of hot soft rock, somewhat like Silly Putty, that, except for a few hard rocks embedded like peanut brittle, normally flows without generating earthquakes. The fracturing of the brittle inclusions, however, may be generating swarms of many small quakes that combine into a faint rumble.
"If tremors are composed of a lot of little earthquakes, each should have a primary and secondary wave just like large quakes," but they would overlap and produce a rumble, said Guilhem.
The stimulation of tremors by shear (tearing) stress rather than by compressional (opening and closing) stress is more consistent with deformation in the fault zone than with underground fluid movement, Nadeau said. The researchers' mapping of the underground tremors also shows that the tremors are not restricted to the plane of the fault, suggesting that faults spread out as they dive into the deeper crust.
Whatever their cause, tremors "are not relieving a lot of stress or making the fault less hazardous, they just indicate a changes in stress next to locked faults," said Nadeau.
Seismologists around the world are searching for tremors along other fault systems, Guilhem noted, although tremors can be hard to detect because of noise from oceans as well as from civilization. Brief tremor activity has been observed on a few faults, triggered by huge quakes far away, and these may be areas to focus on. Tremors were triggered on Northern California's Calaveras Fault by Alaska's Denali quake of 2002, Nadeau said.
The work is supported by the U.S. Geological Survey and the National Science Foundation.
Adapted from materials provided by University of California - Berkeley.

New Envisat images highlight the dramatic retreat of the Aral Sea’s shoreline.

2009-07-11T22:24:00.000-07:00

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ScienceDaily (July 12, 2009) — New Envisat images highlight the dramatic retreat of the Aral Sea’s shoreline from 2006 to 2009. The Aral Sea was once the world’s fourth-largest inland body of water, but it has been steadily shrinking over the past 50 years since the rivers that fed it were diverted for irrigation projects.

By the end of the 1980s, it had split into the Small Aral Sea (north), located in Kazakhstan, and the horse-shoe shaped Large Aral Sea (south), shared by Kazakhstan and Uzbekistan.
By 2000, the Large Aral Sea had split into two – an eastern and western lobe. As visible in the images, the eastern lobe retreated substantially between 2006 and 2009. It appears to have lost about 80% of its water since the 2006 acquisition, at which time the eastern lobe had a length of about 150 km and a width of about 70 km.
The sea’s entire southern section is expected to dry out completely by 2020, but efforts are underway to save the northern part.
The Kok-Aral dike, a joint project of the World Bank and the Kazakhstan government, was constructed between the northern and southern sections of the sea to prevent water flowing into the southern section. Since its completion in 2005, the water level has risen in the northern section by an average of 4 m.
As the Aral Sea evaporated, it left behind a 40 000 sq km zone of dry, white salt terrain now called the Aral Karakum Desert. Each year violent sandstorms pick up at least 150 000 tonnes of salt and sand from the Aral Karakum and transport it across hundreds of km, causing severe health problems for the local population and making regional winters colder and summers hotter. In an attempt to mitigate these effects, vegetation that thrives in dry, saline conditions is being planted in the former seabed.
In 2007, the Kazakhstan government secured another loan from the World Bank to implement the second stage, which includes the building of a second dam, of the project aimed at reversing this man-made environmental disaster.
Envisat acquired these images on 1 July 2006 and 6 July 2009 with its Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution Mode to provide a spatial resolution of 300 m.
Adapted from materials provided by European Space Agency.

Beyond Carbon Dioxide: Growing Importance Of Hydrofluorocarbons (HFCs) In Climate Warming

2009-07-08T23:54:00.000-07:00

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ScienceDaily (July 9, 2009) — Some of the substances that are helping to avert the destruction of the ozone layer could increasingly contribute to climate warming, according to scientists from NOAA's Earth System Research Laboratory and their colleagues in a new study in the journal Proceedings of the National Academy of Sciences.

The authors took a fresh look at how the global use of hydrofluorocarbons (HFCs) is expected to grow in coming decades. Using updated usage estimates and looking farther ahead than past projections (to the year 2050), they found that HFCs—especially from developing countries—will become an increasingly larger factor in future climate warming.
"HFCs are good for protecting the ozone layer, but they are not climate friendly," said David W. Fahey, a scientist at NOAA and second author of the new study. "Our research shows that their effect on climate could become significantly larger than we expected, if we continue along a business-as-usual path."
HFCs currently have a climate change contribution that is small (less than 1 percent) in comparison to the contribution of carbon dioxide (CO2) emissions. The authors have shown that by 2050 the HFCs contribution could rise to 7 to 12 percent of what CO2 contributes. And if international efforts succeed in stabilizing CO2 emissions, the relative climate contribution from HFCs would increase further.
HFCs, which do not contain ozone-destroying chlorine or bromine atoms, are used as substitutes for ozone-depleting compounds such as chlorofluorocarbons (CFCs) in such uses as refrigeration, air conditioning, and the production of insulating foams. The Montreal Protocol, a 1987 international agreement, has gradually phased out the use of CFCs and other ozone-depleting substances, leading to the development of long-term replacements such as HFCs.
Though the HFCs do not deplete the ozone layer, they are potent greenhouse gases. Molecule for molecule, all HFCs are more potent warming agents than CO2 and some are thousands of times more effective. HFCs are in the "basket of gases" regulated under the 1997 Kyoto Protocol, an international treaty to reduce emissions of greenhouse gases.
The new study factored in the expected growth in demand for air conditioning, refrigerants, and other technology in developed and developing countries. The Montreal Protocol's gradual phasing out of the consumption of ozone-depleting substances in developing countries after 2012, along with the complete phase-out in developed countries in 2020, are other factors that will lead to increased usage of HFCs and other alternatives.
Decision-makers in Europe and the United States have begun to consider possible steps to limit the potential climate consequences of HFCs. The PNAS study examined several hypothetical scenarios to mitigate HFC consumption. For example, a global consumption limit followed by a 4 percent annual reduction would cause HFC-induced climate forcing to peak in the year 2040 and then begin to decrease before the year 2050.
"While unrestrained growth of HFC use could lead to significant climate implications by 2050, we have shown some examples of global limits that can effectively reduce the HFCs' impact," said John S. Daniel, a NOAA coauthor of the study.
The authors of the PNAS study are Guus J.M Velders of the Netherlands Environmental Assessment Agency, Fahey and Daniel of NOAA's Earth System Research Laboratory, Mack McFarland of DuPont Fluoroproducts, and Stephen O. Andersen of the U.S. Environmental Protection Agency.
Journal reference:
. The large contribution of projected HFC emissions to future climate forcing. Proceedings of the National Academy of Sciences, June 22, 2009
Adapted from materials provided by National Oceanic and Atmospheric Administration.

Ice Volume Of Switzerland’s Glaciers Calculated

2009-07-08T23:52:00.000-07:00

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ScienceDaily (July 9, 2009) — Swiss glaciers have lost a lot of ice in recent years due to increased melting. As temperatures climb, so do the fears that the glaciers could one day disappear altogether. Until now it could only be estimated approximately how big the ice volume in the Swiss Alps actually is and how it has changed in recent years.

A team of scientists headed by Martin Funk, ETH-Professor at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at ETH Zurich, however, has now developed a novel procedure for determining the ice volume of a glacier. Their results are presented in the current issue of Global and Planetary Change.
The researchers developed the new method according to the law of mass conservation, which states that the surface mass balance has to be balanced by the ice flow and the change in ice thickness. This allows to infer on the ice thickness distribution of a glacier from the surface topography by estimating the mass balance distribution. "The calculation of the current ice volume is the most important indicator in predicting future glacier changes," explains Martin Funk.
74 km3 of glaciers
The scientists applied the procedure to the 59 Swiss glaciers larger than three square kilometers. For the remaining 1’400 glaciers, the ice volume was estimated by using an empirical area-volume approach derived from the new generated data set. The total glacier ice volume in 1999 was estimated to 74 km3, with an accuracy of 9 km3. This means the total volume of all glaciers of Switzerland is smaller than that of the Lake Geneva, which has a water volume of 89 km3. With a glaciated land area of 1’063 km2, the Swiss glaciers have an average ice thickness of 70 meters.
The scientists also discovered that the 59 larger glaciers account for almost 88% of the ice volume, whereas about 24% is stored in the Aletsch region alone (the Oberaletschgletscher, Mittelaletschgletscher and Grosser Aletschgletscher). The area of the Great Aletsch Glacier is approximately the same as the total area of all the Swiss glaciers smaller than one square kilometer. However, they have an overall ice volume that is twenty times smaller than that of the Grosser Aletschgletscher. "This just goes to show that the large glaciers carry the most weight in determining a region’s ice volume," explains Funk.
Volume decreased by 12 percent
The ETH Zurich study also revealed a change in the ice volume since 1999. Over the last decade – the warmest for 150 years – Switzerland’s glaciers have lost 9 km3 of ice (-12%), including 2.6 km³ (-3.5%) in the record-breaking sum-mer of 2003 alone. These figures are all the more alarming as the climate continues to warm up and the temperatures in the Swiss Alps are expected to increase by 1.8 degrees in the winter and 2.7 degrees in the summer by 2050.
Adapted from materials provided by ETH Zurich.

Close Relationship Between Past Warming And Sea-level Rise

2009-07-07T00:21:00.000-07:00

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ScienceDaily (July 7, 2009) — A team from the National Oceanography Centre, Southampton (NOCS), along with colleagues from Tübingen (Germany) and Bristol presents a novel continuous reconstruction of sea level fluctuations over the last 520 thousand years. Comparison of this record with data on global climate and carbon dioxide (CO2) levels from Antarctic ice cores suggests that even stabilisation at today's CO2 levels may commit us to sea-level rise over the next couple of millennia, to a level much higher than long-term projections from the Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).

Little is known about the total amount of possible sea-level rise in equilibrium with a given amount of global warming. This is because the melting of ice sheets is slow, even when temperature rises rapidly. As a consequence, current predictions of sea-level rise for the next century consider only the amount of ice sheet melt that will occur until that time. The total amount of ice sheet melting that will occur over millennia, given the current climate trends, remains poorly understood.
The new record reveals a systematic equilibrium relationship between global temperature and CO2 concentrations and sea-level changes over the last five glacial cycles. Projection of this relationship to today's CO2 concentrations results in a sea-level at 25 (±5) metres above the present. This is in close agreement with independent sea-level data from the Middle Pliocene epoch, 3-3.5 million years ago, when atmospheric CO2 concentrations were similar to the present-day value. This suggests that the identified relationship accurately records the fundamental long-term equilibrium behaviour of the climate system over the last 3.5 Million years.
Lead author Professor Eelco Rohling of the University of Southampton's School of Ocean and Earth Science based at NOCS, said: "Let's assume that our observed natural relationship between CO2 and temperature, and sea level, offers a reasonable 'model' for a future with sustained global warming. Then our result gives a statistically sound expectation of a potential total long-term sea-level rise. Even if we would curb all CO2 emissions today, and stabilise at the modern level (387 parts per million by volume), then our natural relationship suggests that sea level would continue to rise to about 25 m above the present. That is, it would rise to a level similar to that measured for the Middle Pliocene."
Project partners Professor Michal Kucera (University of Tübingen) and Dr Mark Siddall (University of Bristol), add: "We emphasise that such equilibration of sea level would take several thousands of years. But one still has to worry about the large difference between the inferred high equilibrium sea level and the level where sea level actually stands today. Recent geological history shows that times with similarly strong disequilibria commonly saw pulses of very rapid sea-level adjustment, at rates of 1-2 metres per century or higher."
The new study's projection of long-term sea-level change, based on the natural relationship of the last 0.5 to 3.5 million years, differs considerably from the IPCC's model-based long-term projection of +7 m. The discrepancy cannot be easily explained, and new work is needed to ensure that the 'gap is closed'.
The observed relationships from the recent geological past can form a test-bed or reality-check for models, to help them achieve improved future projections.
The project was funded by the Natural Environment Research Council (UK) and the Deutsche Forschungs-Gemeinschaft (Germany).
The authors are Eelco Rohling (NOCS), Katharine Grant (NOCS), Mike Bolshaw (NOCS), Andrew Roberts (NOCS), Mark Siddall (University of Bristol), Christoph Hemleben (University of Tübingen) and Michal Kucera (University of Tübingen).
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Journal reference:
Rohling et al. Antarctic temperature and global sea level closely coupled over the past five glacial cycles. Nature Geoscience, June 21, 2009; DOI: 10.1038/ngeo557
Adapted from materials provided by National Oceanography Centre, Southampton (UK).

Natural Deep Earth Pump Fuels Earthquakes And Ore

2009-07-06T09:22:00.000-07:00

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ScienceDaily (July 6, 2009) — For the first time scientists have discovered the presence of a natural deep earth pump that is a crucial element in the formation of ore deposits and earthquakes.

The process, called creep cavitation, involves fluid being pumped through pores in deformed rock in mid-crustal sheer zones, which are approximately 15 km below the Earth's surface.
The fluid transfer through the middle crust also plays a key role in tectonic plate movement and mantle degassing.
The discovery was made by examining one millimetre sized cubes of exposed rock in Alice Springs, which was deformed around 320 million years ago during a period of natural mountain formation.
The evidence is described in a paper published in the latest edition of Nature entitled Creep cavitation can establish a dynamic granular fluid pump in ductile shear zones.
One of the paper's author's CSIRO Exploration and Mining scientist Dr Rob Hough said that this was the first direct observation of fluids moving through the mid-crustal shear zone.
"We are seeing the direct evidence for one of the processes that got ore forming fluids moving up from the mantle to the shallow crust to form the ore deposits we mine today, it is also one of the mechanisms that can lead to earthquakes in the middle crust," Dr Hough said.
Research leader Dr Florian Fusseis, from the University of Western Australia, said that the discovery could provide valuable information in understanding how earthquakes are formed.
"While we understand reasonably well why earthquakes happen in general, due to stress build-up caused by motions of tectonic plates, the triggering of earthquakes is much more complex," Dr Fusseis said.
"To understand the 'where' and 'when' of earthquakes, the 'how' needs to be understood first. We know that earthquakes nucleate by failure on a small part of a shear zone."
Dr Fusseis said that while their sample did not record an earthquake it gave them an insight into the structures that could be very small and localized precursors of seismic failure planes.
The discovery was made possible through the use of high-resolution Synchrotron X-ray tomographic, scanning electron microscope observations at the nanoscale and advanced visualisation using iVEC in Western Australia.
The authors of the paper propose that the fluid movement, described as the granular fluid pump, is a self sustaining process where pores open and close allowing fluid and gas to be pumped out.
The paper was written by five authors from CSIRO Exploration and Mining working through the Minerals Down Under National Research Flagship, The School of Earth & Environmental Sciences, University of Western Australia and Advanced Photon Source, and Argonne National Laboratory, USA.
Three of the authors are with CSIRO: Prof Klaus Regenauer-Lieb who shares his time between CSIRO and the University of Western Australia and is also a WA Premiers Fellow; Dr Jie Liu and Dr Rob Hough.
The experiments at the Advanced Photon Source in Chicago were funded in part by the Australian Synchrotron Research Program.
Adapted from materials provided by CSIRO Australia.

World's Largest Aerosol Sensing Network Has Leafy Origins

2009-07-05T22:56:00.000-07:00

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ScienceDaily (July 6, 2009) — Twenty years ago, Brent Holben was part of a NASA team studying vegetation from space. In an unlikely career twist, his research morphed into the study of a critical, if overlooked, subplot in the story of climate change.

From his office at NASA's Goddard Space Flight Center in Greenbelt, Md., Holben helps manage the world's largest network of ground-based sensors for aerosols -- tiny specks of solids and liquids that waft about in the atmosphere. These particles come from both human and natural sources and can be observed everywhere in the world.
Scientists know that some of them play an outsized role in Earth's climate. And much of that knowledge has come from the Aerosol Robotic Network, or AERONET, the collaborative, international sensor network which Holben leads.
"Aerosols play a key role in climate, and pretty much everybody who studies aerosols uses data from AERONET," said William Lau, director of the Atmospheric Sciences Division at Goddard. "Without AERONET, our understanding of the climate system simply wouldn't be where it is today."
Trouble Seeing the Forest and the Trees
The origins of AERONET date to the late 1980s, when Goddard researchers were attempting — and struggling — to study vegetation using satellites. "The atmosphere kept getting in the way," Holben said. Satellites couldn't properly sense the vegetation through all the dust, minerals, soot, salt, and other atmospheric aerosols obscuring the view. The problem prompted Holben to put his vegetation research aside "temporarily" to tackle aerosols. In 1992, he planned a field campaign to the Amazon, where farmers were burning swaths of rainforest to clear the land. The heavy emissions from the fires made it an ideal environment to study aerosol particles. During that project, Holben began to develop a method for studying aerosols that became a template for future campaigns. He used lamp-sized instruments called sun-sky photometers to measure the intensity of light filtering through a given column of atmosphere. Aerosol particles scatter or absorb portions of the incoming light, allowing scientists to deduce their size, shape, and chemical composition. Often the instruments are installed on the roofs of universities, but solar-powered versions of the devices can also be deployed in remote corners of the world, far off the grid.
Intriguing results began to emerge from the Amazon campaign as well as others in Africa, Canada, and Hawaii. Though aerosols generally reside in the atmosphere for just a few weeks, the data from the Amazon showed that heavy fires could increase pollution levels dramatically for as long as two months after the burning season ended.
A Time to Plant, A Time to Reap
The timing of Holben's foray into aerosol research turned out to be impeccable. Around the time he was deploying photometers in the Amazon, the volcanic eruption of Mount Pinatubo in the Philippines flooded the atmosphere with sulfate aerosols. The burst blocked some solar radiation from reaching Earth's surface and caused global temperatures to drop by 0.5 °C (0.9 °F) for a few years. The eruption underscored the profound impact sulfate aerosols could have on climate. It also reminded researchers how poorly they understood many other types of aerosols. Deploying more photometers was a logical and relatively low-cost way to start filling the gaps in knowledge. Holben and colleagues slowly set up an array of sensors in the United States, while forging collaborations for similar networks in France, Brazil, Spain, Canada, and Japan. Soon, Holben and his collaborators realized that they had created a global network. In 1998, he described the network's potential in an article in Remote Sensing of Environment, laying out methods of calibrating the sensors and guidelines for collecting and interpreting data. With that paper, AERONET was officially born. Today AERONET consists of approximately 400 sites in 50 countries on all seven continents. There are AERONET stations on remote sand dunes in Mali, on the ice sheet at South Pole, and on the tiny island nation of Nauru in the South Pacific.
An Ever-Wider Net
By providing accurate measurements from the ground, AERONET has emerged as the best tool to validate the accuracy of new satellite instruments. For example, scientists have relied upon AERONET to reconcile differences between aerosol measurements from the Moderate-Resolution Imaging Spectroradiometer (MODIS) and the Multiangle Imaging SpectroRadiometer (MISR), two instruments on NASA's Terra satellite. "Without AERONET, we'd have no baseline for comparison," said Michael Mishchenko, a remote sensing expert at NASA's Goddard Institute for Space Studies in New York City and project scientist for NASA's upcoming Glory mission. Glory will rely on AERONET to validate the Aerosol Polarimetery Sensor, an innovative instrument that will distinguish between different types of aerosols from space. Though developed nations are dense with AERONET stations, coverage in many developing areas remains sparse. That's a problem because aerosols don't recognize borders and they aren't limited to land masses.
Gaps in coverage can lead to gaps in understanding, said Venkatachalam Ramaswamy, director of the National Oceanic and Atmospheric Administration's Geophysical Fluid Dynamics Laboratory and a professor of geosciences at Princeton University, N.J. Compared to other factors that affect climate — such as the output of the Sun or greenhouse gases — aerosols are considered the least-well understood. So Holben and colleagues are working to expand AERONET and continue filling in the gaps. Zhanqing Li, an atmospheric scientist at the University of Maryland, College Park, Md. is leading an international field campaign in China, where aerosol loading is exceptionally high. The scientists are deploying AERONET photometers and other instruments that gather information about the impact of aerosols on the region's climate, especially on the dynamics of the Asian monsoon.
In India, AERONET-affiliated researchers are deploying sensors along the flight track of NASA's CALIPSO satellite, which uses light detection and ranging (LIDAR) to measure aerosols. AERONET's open-source approach to data collection and analysis has also aided its expansion. All data is relayed through weather satellites to a centralized database at Goddard, where it quickly becomes available on the Internet.
"It's always been important to me that AERONET data be freely available," Holben said. "The taxpayers fund this project, and they deserve to know what we're finding."
"Scientists are typically protective of their data, so Holben's insistence on data sharing was a bit avant-garde," said Joel Schafer, a Goddard AERONET scientist. The strategy has paid off. The 1998 study Holben used to introduce AERONET recently passed an impressive academic milestone: it has been cited more than 1,000 times, making it one of the most referenced papers in contemporary earth science. With that accomplishment under his belt, perhaps Holben will have the time to turn back to that old vegetation research.
Adapted from materials provided by NASA/Goddard Space Flight Center. Original article written by Adam Voiland.

Desert Dust Alters Ecology Of Colorado Alpine Meadows

2009-07-05T03:59:00.001-07:00

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ScienceDaily (July 5, 2009) — Accelerated snowmelt--precipitated by desert dust blowing into the mountains--changes how alpine plants respond to seasonal climate cues that regulate their life cycles, according to results of a new study reported this week in the journal Proceedings of the National Academy of Sciences (PNAS). These results indicate that global warming may have a greater influence on plants' annual growth cycles than previously thought.

Current mountain dust levels are five times greater than they were before the mid-19th century, due in large part to increased human activity in deserts.
"Human use of desert landscapes is linked to the life cycles of mountain plants, and changes the environmental cues that determine when alpine meadows will be in bloom, possibly increasing plants' sensitivity to global warming," said Jay Fein, program director in the National Science Foundation (NSF)'s Division of Atmospheric Sciences, which funded the research in part.
This year, 12 dust storms have painted the mountain snowpack red and advanced the retreat of snow cover, likely by more than a month across Colorado.
"Desert dust is synchronizing plant growth and flowering across the alpine zone," said Heidi Steltzer, a Colorado State University scientist who led the study. "Synchronized growth was unexpected, and may have adverse effects on plants, water quality and wildlife."
"It's striking how different the landscape looks as result of this desert-and-mountain interaction," said Chris Landry, director of the Center for Snow and Avalanche Studies (CSAS) in Silverton, Colo., who, along with Tom Painter, director of the Snow Optics Laboratory at the University of Utah, contributed to the study.
"Visitors to the mountains arriving in late June will see little remaining snow," said Landry, "even though snow cover was extensive and deep in April. The snow that remains will be barely distinguishable from the surrounding soils.
Earlier snowmelt by desert dust, said Painter, "depletes the natural water reservoirs of mountain snowpacks and in turn affects the delivery of water to urban and agricultural areas."
With climate change, warming and drying of the desert southwest are likely to result in even greater dust accumulation in the mountains.
In an alpine basin in the San Juan Mountains, the researchers simulated dust effects on snowmelt in experimental plots. They measured dust's acceleration of snowmelt on the life cycles of alpine plants.
The timing of snowmelt signals to mountain plants that it's time to start growing and flowering. When dust causes early snowmelt, plant growth does not necessarily begin soon after the snow is gone.
Instead, plants delay their life cycle until air temperatures have warmed consistently above freezing.
"Climate warming could therefore have a great effect on the timing of growth and flowering," said Steltzer.
Competition for water and nutrient resources among plants should increase, leading to the loss of less competitive species. Delayed plant growth could increase nutrient losses, decreasing water quality.
Similarity in flowering times and plant growth will result in abundant resources for wildlife for a short time rather than staggered resources over the whole summer, Steltzer believes.
"With increasing dust deposition from drying and warming in the deserts," she said, "the composition of alpine meadows could change as some species increase in abundance, while others are lost, possibly forever."
Adapted from materials provided by National Science Foundation.

New Type Of El Nino Could Mean More Hurricanes Make Landfall

2009-07-02T22:40:00.001-07:00

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ScienceDaily (July 3, 2009) — El Niño years typically result in fewer hurricanes forming in the Atlantic Ocean. But a new study suggests that the form of El Niño may be changing potentially causing not only a greater number of hurricanes than in average years, but also a greater chance of hurricanes making landfall, according to climatologists at the Georgia Institute of Technology. The study appears in the July 3, 2009, edition of the journal Science.

"Normally, El Niño results in diminished hurricanes in the Atlantic, but this new type is resulting in a greater number of hurricanes with greater frequency and more potential to make landfall," said Peter Webster, professor at Georgia Tech's School of Earth and Atmospheric Sciences.
That's because this new type of El Niño, known as El Niño Modoki (from the Japanese meaning "similar, but different"), forms in the Central Pacific, rather than the Eastern Pacific as the typical El Niño event does. Warming in the Central Pacific is associated with a higher storm frequency and a greater potential for making landfall along the Gulf coast and the coast of Central America.
Even though the oceanic circulation pattern of warm water known as El Niño forms in the Pacific, it affects the circulation patterns across the globe, changing the number of hurricanes in the Atlantic. This regular type of El Niño (from the Spanish meaning "little boy" or "Christ child") is more difficult to forecast, with predictions of the December circulation pattern not coming until May. At first glance, that may seem like plenty of time. However, the summer before El Niño occurs, the storm patterns change, meaning that predictions of El Niño come only one month before the start of hurricane season in June. But El Niño Modoki follows a different prediction pattern.
"This new type of El Niño is more predictable," said Webster. "We're not sure why, but this could mean that we get greater warning of hurricanes, probably by a number of months."
As to why the form of El Niño is changing to El Niño Modoki, that's not entirely clear yet, said Webster.
"This could be part of a natural oscillation of El Niño," he said. "Or it could be El Niño's response to a warming atmosphere. There are hints that the trade winds of the Pacific have become weaker with time and this may lead to the warming occurring further to the west. We need more data before we know for sure."
In the study, Webster, along with Earth and Atmospheric Sciences Chair Judy Curry and research scientist Hye-Mi Kim used satellite data along with historical tropical storm records and climate models.
The research team is currently looking at La Niña, the cooling of the surface waters in the Eastern and Central Pacific.
"In the past, La Nina has been associated with a greater than average number of North Atlantic hurricanes and La Nina seems to be changing its structure as well," said Webster. "We're vitally interested in understanding why El Niño-La Niña has changed. To determine this we need to run a series of numerical experiments with climate models."
Adapted from materials provided by Georgia Institute of Technology, via EurekAlert!, a service of AAAS.

Sea Ice At Lowest Level In 800 Years Near Greenland

2009-07-02T11:29:00.001-07:00

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ScienceDaily (July 2, 2009) — New research, which reconstructs the extent of ice in the sea between Greenland and Svalbard from the 13th century to the present indicates that there has never been so little sea ice as there is now. The research results from the Niels Bohr Institute, among others, are published in the scientific journal, Climate Dynamics.

There are of course neither satellite images nor instrumental records of the climate all the way back to the 13th century, but nature has its own 'archive' of the climate in both ice cores and the annual growth rings of trees and we humans have made records of a great many things over the years - such as observations in the log books of ships and in harbour records. Piece all of the information together and you get a picture of how much sea ice there has been throughout time.
Modern research and historic records
"We have combined information about the climate found in ice cores from an ice cap on Svalbard and from the annual growth rings of trees in Finland and this gave us a curve of the past climate" explains Aslak Grinsted, geophysicist with the Centre for Ice and Climate at the Niels Bohr Institute at the University of Copenhagen.
In order to determine how much sea ice there has been, the researchers needed to turn to data from the logbooks of ships, which whalers and fisherman kept of their expeditions to the boundary of the sea ice. The ship logbooks are very precise and go all the way back to the 16th century. They relate at which geographical position the ice was found. Another source of information about the ice are records from harbours in Iceland, where the severity of the winters have been recorded since the end of the 18th century.
By combining the curve of the climate with the actual historical records of the distribution of the ice, researchers have been able to reconstruct the extent of the sea ice all the way back to the 13th century. Even though the 13th century was a warm period, the calculations show that there has never been so little sea ice as in the 20th century.
In the middle of the 17th century there was also a sharp decline in sea ice, but it lastet only a very brief period. The greatest cover of sea ice was in a period around 1700-1800, which is also called the 'Little Ice Age'.
"There was a sharp change in the ice cover at the start of the 20th century," explains Aslak Grinsted. He explains, that the ice shrank by 300.000 km2 in the space of ten years from 1910-1920. So you can see that there have been sudden changes throughout time, but here during the last few years we have had some record years with very little ice extent.
"We see that the sea ice is shrinking to a level which has not been seen in more than 800 years", concludes Aslak Grinsted.
Journal reference:
Macias Fauria et al. Unprecedented low twentieth century winter sea ice extent in the Western Nordic Seas since A.D. 1200. Climate Dynamics, 2009; DOI: 10.1007/s00382-009-0610-z
Adapted from materials provided by University of Copenhagen.

Thunderhead Accelerator

2009-07-02T11:18:00.000-07:00

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Besides being host to stunning lightning displays, thunderclouds also emit gamma rays, although researchers aren't completely sure why. Last fall, detectors installed on a mountaintop in Japan captured the first simultaneous observations of this radiation along with the high-speed electrons thought to be their source. The results, detailed in the 26 June Physical Review Letters, support the prevailing model of thundercloud accelerators generating "runaway" electrons, which may sometimes initiate lightning.
Since 1994, satellites, aircraft, and ground-based detectors have picked up gamma ray flashes from thunderstorms. They can last from a few milliseconds to minutes, but only the shortest ones appear to be associated directly with lightning strikes.
Experts believe the gamma rays come from electrons accelerated to near the speed of light in the strong electric fields of thunderclouds. When one of these fast electrons collides with an air molecule it slows down, causing it to emit a gamma ray photon as so-called bremsstrahlung radiation. To account for enough high-speed electrons, theorists have proposed that cosmic rays provide a "seed" population. As these primary electrons accelerate in a thundercloud's electric field, they knock other electrons off of air molecules, and the newly liberated electrons accelerate and knock out still more electrons from atoms. This "runaway" avalanche model is consistent with short flashes, and it may provide the trigger for lightning strikes [1]. But it hasn't been clear whether the model could also explain long-duration bursts.
To provide a new type of data set, Harufumi Tsuchiya of RIKEN, a Japanese research institute, and his colleagues built a system that could measure both the electrons and photons from a thunderstorm. Their main components were a sodium-iodide scintillator that could detect all incoming particles in the range of 10 thousand electron-volts (keV) to 12 million electron-volts (MeV) and a plastic scintillator sensitive primarily to electrons with 500 keV or more energy. Because these relativistic electrons travel at most a few hundred meters through the atmosphere, the detectors were placed 2770 meters above sea level at the Norikura Observatory, where low-lying thunderstorms are frequent.
During a storm on the night of 20 September 2008, the detectors picked up a radiation burst lasting 90 seconds, with no associated lightning strike. A computer model showed that the gamma rays--which were identified by subtracting the two scintillator signals--likely originated from 90 meters above the detectors. "Because of this short source distance, the accelerated electrons were able to arrive at our detector after escaping an acceleration region in the thunderclouds," Tsuchiya says. The team's estimated electron energies extending up to 20 MeV were consistent with the runaway model, suggesting that at least the energy predictions of the theory are reasonable for long-duration gamma-ray bursts.
From the electron counts, the authors also inferred the cloud's accelerator to be 200 meters long. This length is shorter than might be expected from the runaway model, says Robert Roussel-Dupré, a science consultant in Santa Fe, New Mexico, who helped develop the model. He thinks an extension of the theory is needed to explain the size of the accelerator, the long duration of such bursts, and also the puzzlingly small electric fields measured by balloons flown inside thunderclouds. By current theories, these fields aren't large enough to initiate lightning. A clearer picture of long-duration bursts could connect runaway electrons to the lightning spark.--Michael Schirber Michael Schirber is a freelance science writer in Lyon, France.
References:[1] J. R. Dwyer, M. A. Uman, and H. K. Rassoul, "Remote Measurements of Thundercloud Electrostatic Fields," J. Geophys. Res. 114, D09208 (2009) [see Cosmic Rays Offer Clue to Lightning (news article at Physicsworld.com)].

QuikScat Finds Tempests Brewing In 'Ordinary' Storms

2009-07-02T08:21:00.000-07:00

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ScienceDaily (July 2, 2009) — "June is busting out all over," as the song says, and with it, U.S. residents along the Atlantic and Gulf coasts begin to gaze warily toward the ocean, aware that the hurricane season is revving up. In the decade since NASA's QuikScat satellite and its SeaWinds scatterometer launched in June 1999, the satellite has measured the wind speed and wind direction of these powerful storms, providing data that are increasingly used by the National Oceanic and Atmospheric Administration's (NOAA) National Hurricane Center and other world forecasting agencies. The data help scientists detect these storms, understand their wind fields, estimate their intensity and track their movement.

But tropical cyclones aren't the only storms that generate hurricane-force winds. Among others that do is a type of storm that dominates the weather in parts of the United States and other non-tropical regions every fall, winter and into spring: extratropical cyclones.
Extratropical Cyclones: Meteorological 'Bombs'
Scientists have long known that extratropical cyclones (also known as mid-latitude or baroclinic storms) sometimes produce hurricane-force winds. But before QuikScat, hurricane-force extratropical cyclones were thought to be relatively rare. Thanks to QuikScat, we now know that such storms occur much more frequently than previously believed, and the satellite has given forecasters an effective tool for routinely and consistently detecting and forecasting them.
These storms, which occur near busy trans-oceanic shipping lanes, pose a significant threat to life and property for those on the high seas, generating high winds and waves up to 30 meters (100 feet) high. When they make landfall, in areas like Alaska, the Pacific Northwest, New England and the U.S. mid-Atlantic coast, they produce strong winds, high surf, coastal flooding, heavy rains, river flooding and even blizzard conditions.
Take the "Hanukkah Eve" extratropical cyclone of Dec. 14-15, 2006, for example. That storm viciously raked the U.S. Pacific Northwest and British Columbia with torrential rainfall and hurricane-force winds exceeding 87 knots (100 miles per hour) in spots. Dozens of people were injured and 18 people lost their lives, while thousands of trees were downed, power was knocked out for more than 1.5 million residents and structural damage topped $350 million.
NOAA defines an extratropical cyclone as "a storm system that primarily gets its energy from the horizontal temperature contrasts that exist in the atmosphere." These low pressure systems have associated cold fronts, warm fronts and occluded fronts. Tropical cyclones, in contrast, don't usually vary much in temperature at Earth's surface, and their winds are generated by the energy released as clouds and rain form in warm, moist, tropical air. While a tropical cyclone's strongest winds are near Earth's surface, the strongest winds in extratropical cyclones are about 12 kilometers (8 miles) up, in the tropopause. Tropical cyclones can become extratropical, and vice versa.
Extratropical cyclones occur in both the North Atlantic and North Pacific year-round. Those with hurricane-force winds have been observed from September through May. Their frequency typically begins to increase in October, peaks in December and January, and tapers off sharply after March. They can range from less than 100 kilometers (62 miles) in diameter to more than 4,000 kilometers (nearly 2,500 miles) across. They typically last about five days, but their hurricane-force winds are usually short-lived--just 24 hours or less. Because they can intensify rapidly, they're often referred to as meteorological "bombs." Wind speeds in extratropical cyclones can vary from just 10 or 20 knots (12 to 23 miles per hour) to hurricane-force (greater than 63 knots, or 74 miles per hour). During their development, they can trek along at more than 30 knots (35 miles per hour), but they slow down as they mature. At their seasonal peak, up to eight such storms of varying intensity have been observed at once in both the North Atlantic and North Pacific.
Early work by scientists at NASA, NOAA and other organizations demonstrated the effectiveness of using scatterometers for detecting these powerful and destructive winds. Scatterometers work by sending radar signals to the ocean surface and measuring the strength of the radar signals that bounce back. The higher the wind speed, the more the ocean surface is disturbed, and the stronger the reflection that is bounced back to the satellite.
Among those who pioneered these efforts at NASA was Senior Research Scientist Timothy Liu of NASA's Jet Propulsion Laboratory, Pasadena, Calif., who used data from the NASA Scatterometer, the predecessor to QuikScat, to study the transition of tropical cyclones into extratropical storms in 1997. In addition, Robert Atlas of NASA's Goddard Space Flight Center, Greenbelt, Md., demonstrated that scatterometer data were able to improve predictions of extratropical storm strength and location.
Raising Forecaster Awareness
Joe Sienkiewicz, chief of the Ocean Applications Branch at NOAA's Ocean Prediction Center, Camp Springs, Md., says QuikScat data have raised the awareness of forecasters to the occurrence of hurricane-force intensity conditions in extratropical cyclones and have significantly advanced their short-term wind warning and forecast processes.
"QuikScat winds have given forecasters at NOAA's Ocean Prediction Center a high level of situational awareness over the data-sparse waters of the North Atlantic and North Pacific Oceans," he said. "Ocean Prediction Center forecasters daily examine every QuikScat pass and patch of wind and frequently base wind warning and forecast decisions solely on QuikScat winds. Through confidence gained from QuikScat, the National Weather Service began issuing warnings for dangerous hurricane-force winds in extratropical cyclones in December 2000.
"From 10 years of QuikScat, we have learned that hurricane force winds in extratropical cyclones occur more frequently than thought, are most frequent in winter months, and the conditions are most often observed south of the cyclone center," he added.
Over the years, the number of storms observed with hurricane-force winds has steadily increased due to forecasters gaining confidence using the data, and improvements to the QuikScat data. From the fall of 2006 through 2008, NOAA's Ocean Prediction Center identified and issued warnings for 115 separate extratropical cyclones (64 in the Atlantic and 51 in the Pacific) that reached hurricane force.
As confirmed in a 2008 study, QuikScat substantially extends the ability of forecasters to detect hurricane-force wind events in extratropical storms. For the studied case, QuikScat was able to identify more than three-and-a-half times as many hurricane-force events as combined data from the European ASCAT sensor on the METOP-A satellite, directly-measured buoy and ship information, and model predictions.
Another study in 2002 found that incorporating QuikScat data increased the number of wind warnings the Ocean Prediction Center issued for extratropical cyclones by 30 percent in the North Atlantic and by 22 percent in the North Pacific. Between 2003 and 2006, the Ocean Prediction Center's forecasters successfully predicted hurricane-force winds two days in advance 58 percent of the time in the Atlantic and 44 percent in the Pacific. Considering that a successful forecast of hurricane-force winds requires accurate prediction of the timing and intensity of an explosive deepening cyclone, these numbers are impressive.
QuikScat data have been instrumental in the ability to forecast hurricane-force extratropical cyclones several days in advance, while they are still well out over the ocean. Forecasters can use the data to determine which numerical weather prediction models are handling a storm the best, thereby improving the accuracy of forecasts and increasing warning lead times. QuikScat data are available to forecasters within three hours of acquisition.
The availability of a consistent observing capability for extratropical cyclones from QuikScat has allowed NOAA to add a third "hurricane-force" warning category for extratropical cyclone winds, in addition to gale and storm, providing better warnings of a coming storm's severity. The U.S. Coast Guard broadcasts these warnings by radiofax, and they are posted online at: http://www.opc.ncep.noaa.gov .
A Boon to Shipping
These extratropical cyclone warnings have a great economic impact on the $200 billion global marine shipping industry. A recent study estimates improvements to warning and forecast services due to QuikScat save the container and bulk shipping industry $135 million a year by reducing their exposure to hurricane-force wind conditions in non-tropical storms over the North Pacific and North Atlantic. Without QuikScat, the severity of many extratropical cyclones would not be determined. The data are also vital to the fishing industry, offshore energy industries, search and rescue organizations, and agencies that track and manage marine hazards like oil spills.
Paul Chang, ocean winds science team lead at NOAA's National Environmental Satellite, Data and Information Service/Center for Satellite Applications and Research, Camp Springs, Md., said ocean vector wind measurements from QuikScat have become a basic part of NOAA's day-to-day forecasting and warning processes.
"The 10 years of observations from the QuikScat mission have provided critical information for the monitoring, modeling, forecasting and research of the atmosphere, oceans and climate," he said.
For more information about QuickScat, visit http://winds.jpl.nasa.gov/.
Adapted from materials provided by NASA/Jet Propulsion Laboratory.

Rising Acidity Levels Could Trigger Shellfish Revenue Declines, Job Losses

2009-07-01T08:40:00.001-07:00

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ScienceDaily (July 1, 2009) — Changes in ocean chemistry — a consequence of increased carbon dioxide (CO2) emissions from human industrial activity — could cause U.S. shellfish revenues to drop significantly in the next 50 years, according to a new study by researchers at the Woods Hole Oceanographic Institution (WHOI).

Intensive burning of fossil fuels and deforestation over the last two centuries have increased CO2 levels in the atmosphere by almost 40 percent. The oceans have absorbed about one-third of all human-generated carbon emissions, but the buildup of CO2 in the ocean is pushing surface waters toward more acidic conditions.
This “ocean acidification” creates a corrosive environment for marine organisms such as corals, marine plankton, and shellfish that build carbonate shells or skeletons. Mollusks — including mussels and oysters, which support valuable marine fisheries — are particularly sensitive to these changes.
In a case study of U.S. commercial fishery revenues published in the June issue of Environmental Research Letters, WHOI scientists Sarah Cooley and Scott Doney calculated the possible economic effects of ocean acidification over the next 50 years using atmospheric CO2 trajectories from the Intergovernmental Panel on Climate Change and laboratory studies of acidification’s effects on shell-forming marine organisms, focusing especially on mollusks.
Mollusk sales by fishermen currently generate about $750 million per year — nearly 20 percent of total U.S. fisheries revenue. The study assumed that mollusks harvests in the U.S. would drop 10 to 25 percent in 50 years’ time as a result of increasing acidity levels, which would decrease these mollusk sales by $75 to $187 million dollars annually.
“Losses in primary revenue from commercial mollusk harvests—or the money that fisherman receive for their catch—could add up to as much as $1.4 billion by 2060,” said Cooley.
Reduced harvests of mollusks, as well as losses of predatory fish and other species that depend on mollusks for food, could lead to economic hardships for fishing communities.
“Ocean acidification will impact the millions of people that depend on seafood and other ocean resources for their livelihoods,” said Doney. “Losses of crustaceans, bivalves, their predators, and their habitat — in the case of reef-associated fish communities — would particularly injure societies that depend heavily on consumption and export of marine resources.”
Because changes in seawater chemistry are already apparent and will grow over the next few decades, Cooley and Doney suggest measures that focus on adaptation to future CO2 increases to lessen the impact on marine ecosystems, such as flexible fishery management plans and support for fishing communities.
“Limiting nutrient runoff from land helps coastal ecosystems stay healthy,” said Cooley. “Also fishing rules can be adjusted to reduce pressure on valuable species; fisheries managers may set up more marine protected areas, or they may encourage development of new fisheries.”
This research was supported by grants from the National Science Foundation and Woods Hole Oceanographic Institution.
Journal reference:
Cooley et al. Anticipating ocean acidification's economic consequences on commercial fisheries. Environmental Research Letters, June 1, 2009; 4 (2): 024007 DOI: 10.1088/1748-9326/4/2/024007
Adapted from materials provided by Woods Hole Oceanographic Institution.

NASA, Japan Release Most Complete Topographic Map Of Earth

2009-07-01T05:32:00.000-07:00

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ScienceDaily (July 1, 2009) — NASA and Japan has released a new digital topographic map of Earth Monday that covers more of our planet than ever before. The map was produced with detailed measurements from NASA's Terra spacecraft.

The new global digital elevation model of Earth was created from nearly 1.3 million individual stereo-pair images collected by the Japanese Advanced Spaceborne Thermal Emission and Reflection Radiometer, or Aster, instrument aboard Terra. NASA and Japan's Ministry of Economy, Trade and Industry, known as METI, developed the data set. It is available online to users everywhere at no cost.
"This is the most complete, consistent global digital elevation data yet made available to the world," said Woody Turner, Aster program scientist at NASA Headquarters in Washington. "This unique global set of data will serve users and researchers from a wide array of disciplines that need elevation and terrain information."
According to Mike Abrams, Aster science team leader at NASA's Jet Propulsion Laboratory in Pasadena, Calif., the new topographic information will be of value throughout the Earth sciences and has many practical applications. "Aster's accurate topographic data will be used for engineering, energy exploration, conserving natural resources, environmental management, public works design, firefighting, recreation, geology and city planning, to name just a few areas," Abrams said.
Previously, the most complete topographic set of data publicly available was from NASA's Shuttle Radar Topography Mission. That mission mapped 80 percent of Earth's landmass, between 60 degrees north latitude and 57 degrees south. The new Aster data expand coverage to 99 percent, from 83 degrees north latitude and 83 degrees south. Each elevation measurement point in the new data is 30 meters (98 feet) apart.
"The Aster data fill in many of the voids in the shuttle mission's data, such as in very steep terrains and in some deserts," said Michael Kobrick, Shuttle Radar Topography Mission project scientist at JPL. "NASA is working to combine the Aster data with that of the Shuttle Radar Topography Mission and other sources to produce an even better global topographic map."
NASA and METI are jointly contributing the Aster topographic data to the Group on Earth Observations, an international partnership headquartered at the World Meteorological Organization in Geneva, Switzerland, for use in its Global Earth Observation System of Systems. This "system of systems" is a collaborative, international effort to share and integrate Earth observation data from many different instruments and systems to help monitor and forecast global environmental changes.
NASA, METI and the U.S. Geological Survey validated the data, with support from the U.S. National Geospatial-Intelligence Agency and other collaborators. The data will be distributed by NASA's Land Processes Distributed Active Archive Center at the U.S. Geological Survey's Earth Resources Observation and Science Data Center in Sioux Falls, S.D., and by METI's Earth Remote Sensing Data Analysis Center in Tokyo.
Aster is one of five Earth-observing instruments launched on Terra in December 1999. Aster acquires images from the visible to the thermal infrared wavelength region, with spatial resolutions ranging from about 15 to 90 meters (50 to 300 feet). A joint science team from the U.S. and Japan validates and calibrates the instrument and data products. The U.S. science team is located at JPL.
For visualizations of the new Aster topographic data, visit: http://www.nasa.gov/topics/earth/features/20090629.html .
Data users can download the Aster global digital elevation model at: https://wist.echo.nasa.gov/~wist/api/imswelcome and http://www.gdem.aster.ersdac.or.jp .

Adapted from materials provided by NASA/Jet Propulsion Laboratory.

How Aerosols Contribute To Climate Change

2009-06-23T05:43:00.000-07:00

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ScienceDaily (June 23, 2009) — What happens in Vegas may stay in Vegas, but what happens on the way there is a different story.

As imaged by Lynn Russell, a professor of atmospheric chemistry at Scripps Institution of Oceanography at UC San Diego, and her team, air blown by winds between San Diego and Las Vegas gives the road to Sin City a distinctive look.
The team has sampled air from the tip of the Scripps Pier since last year, creating a near real-time record of what kinds of particles — from sea salt to car exhaust — are floating around at any given time. Add data about wind speed and direction and the scientists can tell where particles came from and can map their pathways around Southern California.
When Russell and her students put it all together, the atmosphere of greater San Diego comes alive in colors representing the presence of different airborne chemical compounds in aerosol form. One streak of deep red draws a distinct line from the pier that sometimes extends all the way to Las Vegas. The red denotes organic mass, a carbon-based component of vehicular and industrial emissions that pops up on Russell’s readouts frequently. Plot the streak on a road atlas and it reveals the daily life of pollution in Southern California. For one stretch of time, it neatly traced Interstate 15 all the way past the California-Nevada border.
“We were really surprised,” said Russell. “We did not expect to have such consistent winds for the selected study days.”
The hunt for various types of aerosols is helping Russell draw new kinds of global maps, ones that depict what organic compounds—whether natural or from sources such as Southern California traffic and industries—could do to affect rainfall, snowfall, atmospheric warming and cooling, and a host of other climate phenomena. Russell is part of an effort that involves several researchers at Scripps and UCSD and around the world. Collectively they are attempting to address a human-caused phenomenon in the Earth system scarcely considered before the last decade.
Aerosol research is considered one of the most critical frontiers of climate change science, much of which is devoted to the creation of accurate projections of future climate. These projections are generated by computer models — simulations of phenomena such as warming patterns, sea level fluctuations, or drought trends. The raw data for the models can come from historical records of climate basics like temperature and precipitation, but scientists often must rely on incomplete data and best guesses to represent more complex phenomena. The more such uncertainty goes into a model, the greater its margin of error becomes, making it less reliable as a guide for forecasts and adaptive actions.
Among these complex phenomena, the actions of aerosols are what some researchers consider the field’s holy grail, representing the biggest barrier to producing accurate representations of climate. In fact, the Intergovernmental Panel on Climate Change in 2007 specifically listed the effect of aerosols on cloud formation as the largest source of uncertainty in present-day climate models.
Bits of dust, sea salt, the remnants of burned wood, and even living things like bacteria all add to the mix of aerosols that create the skeletons on which clouds form. Around these particles, water and ice condense and cluster into cloud masses. The size and number of each of these droplets determine whether the clouds can produce rain or snow.
The aerosols are also influencing climate in other ways. Diesel exhaust, industrial emissions, and the smoke from burning wood and brush eject myriad bits of black carbon, usually in the form of soot, into the sky and form so-called “brown clouds” of smog. This haze has a dual heating and cooling effect. The particles absorb heat and make the air warmer at the altitudes to which they tend to rise but they also deflect sunlight back into space. This shading effect cools the planet at ground level.
The Arctic Circle is one of the places in the world most sensitive to changes in the mix of aerosols. Since the beginnings of the Industrial Revolution, scientists and explorers have noted the presence of the Arctic haze, a swirl of pollution that appears when sunlight returns after a winter of darkness. The presence of smog over a mostly uninhabited region leads many scientists to believe it is the reason the Arctic is experiencing the most rapid climate-related changes in the world. The haze now lingers for a longer period of time every year. It may be contributing to the forces now causing a meltdown of Arctic ice, a release of methane once stored in permafrost, and a host of ecological changes affecting the spectrum of organisms from mosquitoes to polar bears.
Russell has taken part in two recent analyses of polar air to understand where its imported aerosols come from and how the chemical components of those aerosols could be affecting temperature and cloud formation. From a research vessel in the Norwegian Sea and via continuous measurements from a ground station in Barrow, Alaska, Russell’s team is analyzing particles likely to have been blown to the Arctic from Europe and Asia. Her group has just compiled a full season of air samples fed through intake valves onto filters collected at Barrow.
With it, she believes she has proven what colleagues have previously theorized about where the particles are coming from. She is especially interested in organic particles—aerosols containing carbon supplied either by natural sources such as ocean or land plants or by human sources. Work in her group has shown that organics in the spring haze carry a signature consistent with dust and biomass burning taking place most likely in Siberia. The chemical signature changes in other seasons, revealing itself in infrared spectroscopy readings to be the product of aerosols from natural sources.
The aerosols could be influencing how much snowfall the Arctic gets and keeps. Human-produced aerosols are thought to stifle precipitation in some areas but may provide the impetus for torrential rain in others depending on their chemical make-up. Even if the Asian aerosols are not affecting precipitation, however, Russell said they appear to cool the Arctic atmosphere by deflecting light into space. At the same time, there is strong evidence that they are accelerating ice melt in the Arctic by darkening and heating ice once they fall to the ground the way a dark sweater makes its wearer hotter on a sunny day than does a white sweater.
Russell has been part of another collaborative effort launched in 2008, the International Polar Year, that created chemical profiles of relatively untainted air off the Norwegian west coast, which is only occasionally tinged by European smog. She has also teamed with collaborators at Scripps, NOAA and other universities to profile aerosols around Houston, Texas, and Mexico City.
In the latter two projects, she has provided evidence that agriculture adds more to the aerosol mix in an oil town like Houston than previously thought and that organic particles in Mexico City, rising from the smoke of street vendors and exhaust of cars driving on gas formulated differently than in the United States, glom on to dust in a different manner than American pollution to create aerosols with distinct chemical structures. Figuring out what they do locally and regionally is the next step.
Russell collaborates with a number of other faculty at UCSD whose research also focuses on aerosols, such as Kim Prather, an atmospheric chemistry professor with joint appointments at Scripps and the UCSD Department of Chemistry and Biochemistry. Russell and Prather are comparing their results form Mexico City in an effort to better understand the sources of aerosols in the atmosphere.
“We are trying to understand the major sources of aerosols in our atmosphere and how they affect the overall temperature of our planet; as opposed to greenhouse gases which we know are warming, aerosols can cool or warm depending on their composition and where they are located in the atmosphere," said Prather. Like Russell, Prather also studies long-range transport of aerosols from terrestrial and marine sources. Prather and Russell have worked together on several other projects and recently helped form the Aerosol Chemistry and Climate Institute, a collaboration between Scripps and the Department of Energy’s Pacific Northwest National Laboratory.
For her most comprehensive study, Russell need only to make her shortest journey to the end of Scripps Pier. It is possible that aerosol journeys of a thousand miles or more might be explained by shorter commutes between Southern California counties. Complete analysis of the Interstate 15 data suggests Vegas might not be a source of dirtiness after all. Using data collected over longer time periods, Russell’s pollution map of local counties now suggests organic human-made aerosols might just be blowing toward Nevada from San Bernardino and Riverside then back toward San Diego as winds shift. Russell employs a suite of complementary measurements at the pier to characterize short- and long-term aerosol trends. Those are combined with particle profiles made by Prather’s group and collaborators whose numbers are growing out of necessity.
“Understanding the big picture is the only way we’re going to be able to reduce the uncertainty associated with aerosol particles and their effects on climate,” said Russell. “There are so many parameters, there’s no one instrument or even one person who can do all of it at once.”
Adapted from materials provided by University of California, San Diego, via Newswise.

Carbon Dioxide Higher Today Than Last 2.1 Million Years

2009-06-22T06:37:00.001-07:00

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ScienceDaily (June 21, 2009) — Researchers have reconstructed atmospheric carbon dioxide levels over the past 2.1 million years in the sharpest detail yet, shedding new light on its role in the earth's cycles of cooling and warming.

The study, in the June 19 issue of the journal Science, is the latest to rule out a drop in CO2 as the cause for earth's ice ages growing longer and more intense some 850,000 years ago. But it also confirms many researchers' suspicion that higher carbon dioxide levels coincided with warmer intervals during the study period.
The authors show that peak CO2 levels over the last 2.1 million years averaged only 280 parts per million; but today, CO2 is at 385 parts per million, or 38% higher. This finding means that researchers will need to look back further in time for an analog to modern day climate change.
In the study, Bärbel Hönisch, a geochemist at Lamont-Doherty Earth Observatory, and her colleagues reconstructed CO2 levels by analyzing the shells of single-celled plankton buried under the Atlantic Ocean, off the coast of Africa. By dating the shells and measuring their ratio of boron isotopes, they were able to estimate how much CO2 was in the air when the plankton were alive. This method allowed them to see further back than the precision records preserved in cores of polar ice, which go back only 800,000 years.
The planet has undergone cyclic ice ages for millions of years, but about 850,000 years ago, the cycles of ice grew longer and more intense—a shift that some scientists have attributed to falling CO2 levels. But the study found that CO2 was flat during this transition and unlikely to have triggered the change.
"Previous studies indicated that CO2 did not change much over the past 20 million years, but the resolution wasn't high enough to be definitive," said Hönisch. "This study tells us that CO2 was not the main trigger, though our data continues to suggest that greenhouse gases and global climate are intimately linked."
The timing of the ice ages is believed to be controlled mainly by the earth's orbit and tilt, which determines how much sunlight falls on each hemisphere. Two million years ago, the earth underwent an ice age every 41,000 years. But some time around 850,000 years ago, the cycle grew to 100,000 years, and ice sheets reached greater extents than they had in several million years—a change too great to be explained by orbital variation alone.
A global drawdown in CO2 is just one theory proposed for the transition. A second theory suggests that advancing glaciers in North America stripped away soil in Canada, causing thicker, longer lasting ice to build up on the remaining bedrock. A third theory challenges how the cycles are counted, and questions whether a transition happened at all.
The low carbon dioxide levels outlined by the study through the last 2.1 million years make modern day levels, caused by industrialization, seem even more anomalous, says Richard Alley, a glaciologist at Pennsylvania State University, who was not involved in the research.
"We know from looking at much older climate records that large and rapid increase in CO2 in the past, (about 55 million years ago) caused large extinction in bottom-dwelling ocean creatures, and dissolved a lot of shells as the ocean became acidic," he said. "We're heading in that direction now."
The idea to approximate past carbon dioxide levels using boron, an element released by erupting volcanoes and used in household soap, was pioneered over the last decade by the paper's coauthor Gary Hemming, a researcher at Lamont-Doherty and Queens College. The study's other authors are Jerry McManus, also at Lamont; David Archer at the University of Chicago; and Mark Siddall, at the University of Bristol, UK.
Funding for the study was provided by the National Science Foundation.
Journal reference:
. Atmospheric Carbon Dioxide Concentrations Across the Mid-Pleistocene Transition. Science, June 19, 2009
Adapted from materials provided by The Earth Institute at Columbia University.

Maybe It's Raining Less Than We Thought: Physicists Make A Splash With Raindrops Discovery

2009-06-12T10:26:00.001-07:00

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ScienceDaily (June 11, 2009) — It's conventional wisdom in atmospheric science circles: Large raindrops fall faster than smaller drops because they have a greater terminal speed -- i.e., the speed when the downward force of gravity is exactly the same as the upward air resistance.

Now two physicists from Michigan Technological University and colleagues at the Universidad Nacional Autónoma de México (National University of Mexico) have discovered that it ain't necessarily so.
Some smaller raindrops can fall faster than bigger ones. In fact, they can fall faster than their terminal speed. In other words, they can fall faster than drops that size and weight are supposed to be able to fall.
And that could mean that the weatherman has been overestimating how much it rains.
The findings of Michigan Tech physics professors Alexander Kostinski and Raymond Shaw—co-authors with Guillermo Montero-Martinez and Fernando Garcia-Garcia on a paper scheduled for publication online June 13, 2009, in the American Geophysical Union's journal Geophysical Research Letters—could improve the accuracy of weather measurement and prediction.
The researchers gathered data during natural rainfalls at the Mexico City campus of the National University of Mexico. They studied approximately 64,000 raindrops over three years, using optical array spectrometer probes and a particle analysis and collecting system. They also modified an algorithm or computational formula to analyze the raindrop sizes.
They found clusters of raindrops falling faster than their terminal speed, and as the rainfall became heavier, they saw more and more of these unexpectedly speedy drops. They think that the "super-terminal" drops come from the break-up of larger drops, which produces smaller fragments all moving at the same speed as their parent raindrop and faster than the terminal speed predicted by their size.
"In the past, people have seen indications of faster-than-terminal drops, but they always attributed it to splashing on the instruments," Shaw explains. He and his colleagues took special precautions to prevent such interference, including collecting data only during extremely calm conditions.
Their findings could significantly alter physicists' understanding of the physics of rain.
"Existing rain models are based on the assumption that all drops fall at their terminal speed, but our data suggest that this is not the case," Shaw and Kostinski say. If rainfall is measured based on that assumption, large raindrops that are not really there will be recorded.
"If we want to forecast weather or rain, we need to understand the rain formation processes and be able to accurately measure the amount of rain," Shaw pointed out.
Taking super-terminal raindrops into account could be of real economic benefit, even if it leads only to incremental improvements in precipitation measurement and forecasting. Approximately one-third of the economy—including agriculture, construction and aviation—is directly influenced by the ability to predict precipitation accurately. "And one-third of the economy is a very large sum of money, even during a recession," Shaw remarks.
The physicists' research was supported in part by the National Science Foundation.
Adapted from materials provided by Michigan Technological University.

Typhoons Trigger Slow Earthquakes

2009-06-12T10:16:00.000-07:00

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ScienceDaily (June 12, 2009) — Scientists have made the surprising finding that typhoons trigger slow earthquakes, at least in eastern Taiwan. Slow earthquakes are non-violent fault slippage events that take hours or days instead of a few brutal seconds to minutes to release their potent energy. The researchers discuss their data in a study published the June 11, issue of Nature.

"From 2002 to 2007 we monitored deformation in eastern Taiwan using three highly sensitive borehole strainmeters installed 650 to 870 feet (200-270 meters) deep. These devices detect otherwise imperceptible movements and distortions of rock," explained coauthor Selwyn Sacks of Carnegie's Department of Terrestrial Magnetism. "We also measured atmospheric pressure changes, because they usually produce proportional changes in strain, which we can then remove."
Taiwan has frequent typhoons in the second half of each year but is typhoon free during the first 4 months. During the five-year study period, the researchers, including lead author Chiching Liu (Academia Sinica, Taiwan), identified 20 slow earthquakes that each lasted from hours to more than a day. The scientists did not detect any slow events during the typhoon-free season. Eleven of the 20 slow earthquakes coincided with typhoons. Those 11 were also stronger and characterized by more complex waveforms than the other slow events.
"These data are unequivocal in identifying typhoons as triggers of these slow quakes. The probability that they coincide by chance is vanishingly small," remarked coauthor Alan Linde, also of Carnegie.
How does the low pressure trigger the slow quakes? The typhoon reduces atmospheric pressure on land in this region, but does not affect conditions at the ocean bottom, because water moves into the area and equalizes pressure. The reduction in pressure above one side of an obliquely dipping fault tends to unclamp it. "This fault experiences more or less constant strain and stress buildup," said Linde. "If it's close to failure, the small perturbation due to the low pressure of the typhoon can push it over the failure limit; if there is no typhoon, stress will continue to accumulate until it fails without the need for a trigger."
"It's surprising that this area of the globe has had no great earthquakes and relatively few large earthquakes," Linde remarked. "By comparison, the Nankai Trough in southwestern Japan, has a plate convergence rate about 4 centimeters per year, and this causes a magnitude 8 earthquake every 100 to 150 years. But the activity in southern Taiwan comes from the convergence of same two plates, and there the Philippine Sea Plate pushes against the Eurasian Plate at a rate twice that for Nankai."
The researchers speculate that the reason devastating earthquakes are rare in eastern Taiwan is because the slow quakes act as valves, releasing the stress frequently along a small section of the fault, eliminating the situation where a long segment sustains continuous high stresses until it ruptures in a single great earthquake. The group is now expanding their instrumentation and monitoring for this research.
Adapted from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Ancient Volcanic Eruptions Caused Global Mass Extinction

2009-06-05T07:26:00.001-07:00

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ScienceDaily (May 30, 2009) — A previously unknown giant volcanic eruption that led to global mass extinction 260 million years ago has been uncovered by scientists at the University of Leeds.

The eruption in the Emeishan province of south-west China unleashed around half a million cubic kilometres of lava, covering an area 5 times the size of Wales, and wiping out marine life around the world.
Unusually, scientists were able to pinpoint the exact timing of the eruption and directly link it to a mass extinction event in the study published in Science. This is because the eruptions occurred in a shallow sea – meaning that the lava appears today as a distinctive layer of igneous rock sandwiched between layers of sedimentary rock containing easily datable fossilised marine life.
The layer of fossilised rock directly after the eruption shows mass extinction of different life forms, clearly linking the onset of the eruptions with a major environmental catastrophe.
The global effect of the eruption is also due to the proximity of the volcano to a shallow sea. The collision of fast flowing lava with shallow sea water caused a violent explosion at the start of the eruptions – throwing huge quantities of sulphur dioxide into the stratosphere.
"When fast flowing, low viscosity magma meets shallow sea it's like throwing water into a chip pan – there's spectacular explosion producing gigantic clouds of steam," explains Professor Paul Wignall, a palaeontologist at the University of Leeds, and the lead author of the paper.
The injection of sulphur dioxide into the atmosphere would have lead to massive cloud formation spreading around the world - cooling the planet and ultimately resulting in a torrent of acid rain. Scientists estimate from the fossil record that the environmental disaster happened at the start of the eruption.
"The abrupt extinction of marine life we can clearly see in the fossil record firmly links giant volcanic eruptions with global environmental catastrophe, a correlation that has often been controversial," adds Professor Wignall.
Previous studies have linked increased carbon dioxide produced by volcanic eruptions with mass extinctions. However, because of the very long term warming effect that occurs with increased atmospheric carbon dioxide (as we see with current climate change) the causal link between global environmental changes and volcanic eruptions has been hard to confirm.
This work was done in collaboration with the Chinese University of Geosciences in Wuhan and funded by a grant from the Natural Environment Research Council, UK.
Journal reference:
Paul B. Wignall, Yadong Sun, David P. G. Bond, Gareth Izon, Robert J. Newton, Stéphanie Védrine, Mike Widdowson, Jason R. Ali, Xulong Lai, Haishui Jiang, Helen Cope, and Simon H. Bottrell. Precise coincidence of explosive volcanism, mass extinction and carbon isotope fluctuations in the Middle Permian of China. Science, 2009; DOI: 10.1126/science.1171956
Adapted from materials provided by University of Leeds.

Height Of Large Waves Changes According To Month

2009-06-05T06:50:00.001-07:00

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ScienceDaily (June 2, 2009) — A team of researchers from the University of Cantabria has developed a statistical model that makes it possible to study the variability of extreme waves throughout the year. Their study has shown that there are seasonal variations in the height of waves reaching Spain's coasts, and stresses the importance of this data in planning and constructing marine infrastructures.

"Anybody who observes waves can see that they are not the same height in winter and summer, but rather that their height varies over time, and we have applied a ‘non- seasonal' statistical model in order to measure extreme events such as these," says Fernando J. Méndez, an engineer at the Institute of Environmental Hydraulics at the University of Cantabria and co-author of a study published recently in the journal Coastal Engineering.
The new model can chart the pattern of extreme waves "with a greater degree of reliability", by studying ‘significant wave height' (Hs) in relation to a specific return period. The Hs is the representative average height of the sea, provided by buoys (it is calculated by measuring one in three of the highest waves), and the return period is the average time needed for the event to happen.
For example, if a wave height of 15 metres is established at a certain point on the coast with a return period of 100 years, this means that, on average, a wave of 15 metres could reach this point once every 100 years. "This can be very useful when it comes to building an oil platform in the sea or a particular piece of coastal infrastructure", explains Méndez.
The researchers have used data recorded between 1984 and 2003 by five coastal buoys located near the cities of Bilbao, in Vizcaya; Gijón, in Asturias; La Coruña, Cádiz and Valencia in order to demonstrate the validity of their model. The results show that extreme Hs values vary according to location and the month of the year.
The meteorological component of extreme waves
The results showed a similar seasonal variation between waves in Bilbao and Gijón, with waves being less than four metres high between May and September, but increasing after this to reach an average height of seven metres between December and January. The period of large waves in La Coruña extends from October to April, because of the city's westerly position and resulting exposure to more prolonged winter storms.
The Atlantic coast of Cádiz, meanwhile, reflects the characteristic calm of this area of sea between July and September, with Hs values below two metres. The figures for December and January, however, can vary a great deal from one year to another, reaching wave heights in excess of six metres.
Waves on the Mediterranean coast at Valencia measure between 3 and 3.5 metres from September until April, although the graphics reveal two peaks during this period, one of which coincides with the start of spring and the other with the autumn months, during which the phenomenon of the gota fría occurs. (Gota fría events are atmospheric cold air pools that cause rapid, torrential and very localised downpours and high winds).
"All these data are of vital importance in terms of coastal management, since they can establish the risk of flooding and are indispensable for the carrying out of marine construction work, for example infrastructure built close to the coast," says Melisa Menéndez, another of the study's authors. "In addition, they make it possible to calculate the likelihood of a maritime storm occurring."
The researcher also stresses that this information could be very useful in helping to better understand some biological processes, such as how the distribution of marine animals is affected by wave swell, and seaweed growth rates, as well as geological processes, such as how particulates and sediments are transported along the coast.
Extreme value theory
The model developed by the Spanish scientists is based on ‘extreme value theory', a recently-developed statistical discipline that aims to quantify the random behaviour of extreme events. The latest advances in this field have made it possible to better study climatic variability at various scales - over a year (seasonality), over consecutive years or decades (which allows climatic patterns to be derived), and over the long term (providing trends).
The study into extreme waves is on the seasonal scale, but the team has also studied extreme sea level values over almost a 100-year period, thanks to data gathered during the 20th Century by a mareograph located in Newlyn, in the United Kingdom. The scientists have already started to obtain information about extreme swell and sea level values at global level as part of a United Nations project to study the sea's impacts on coasts all over the planet, and how these affect climate change.
Journal references:
Melisa Menéndez, Fernando J. Méndez, Cristina Izaguirre, Alberto Luceño e Inigo J. Losada. The influence of seasonality on estimating return values of significant wave height. Coastal Engineering, 2009; 56 (3): 211 DOI: 10.1016/j.coastaleng.2008.07.004
Melisa Menendez, Fernando J. Mendez and Inigo J. Losada. Forecasting seasonal to interannual variability in extreme sea levels. ICES Journal of Marine Science, 2009; DOI: 10.1093/icesjms/fsp095
Adapted from materials provided by Plataforma SINC, via AlphaGalileo.

Huge undersea mountain found off Indonesia: scientists

2009-05-29T23:30:00.001-07:00

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This aerial view shows new homes being constructed to the north of Banda Aceh on the island of Sumatra in 2006. A massive underwater mountain discovered off the Indonesian island of Sumatra could be a volcano with potentially catastrophic power, a scientist said Friday.
A massive underwater mountain discovered off the Indonesian island of Sumatra could be a volcano with potentially catastrophic power, a scientist said Friday.

Indonesian government marine geologist Yusuf Surachman said the mountain was discovered earlier this month about 330 kilometres (205 miles) west of Bengkulu city during research to map the seabed's seismic faultlines.
The cone-shaped mountain is 4,600 metres (15,100 feet) high, 50 kilometres in diameter at its base and its summit is 1,300 metres below the surface, he said.
"It looks like a volcano because of its conical shape but it might not be. We have to conduct further investigations," he told AFP.
He denied reports that researchers had confirmed the discovery of a new volcano, insisting that at this stage it could only be described as a "seamount" of the sort commonly found around the world.
"Whether it's active or dangerous, who knows?" he added.
The ultra-deep geological survey was conducted with the help of French scientists and international geophysical company CGGVeritas.
The scientists hope to gain a clearer picture of the undersea lithospheric plate boundaries and seafloor displacement in the area, the epicentre of the catastrophic Asian quake and tsunami of 2004.
The tsunami killed more than 220,000 people across Asia, including 168,000 people in Aceh province on the northern tip of Sumatra.
Indonesia is on the so-called Pacific "Ring of Fire," where the meeting of continental plates causes high volcanic and seismic activity.
(c) 2009 AFP

Ocean Circulation Doesn't Work As Expected

2009-05-14T00:18:00.000-07:00

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This model of North Atlantic currents has been called into question by new data from Duke University and the Woods Hole Oceanographic Institution. Image: Archana Gowda, Duke
(PhysOrg.com) -- The familiar model of Atlantic ocean currents that shows a discrete "conveyor belt" of deep, cold water flowing southward from the Labrador Sea is probably all wet.

New research led by Duke University and the Woods Hole Oceanographic Institution relied on an armada of sophisticated floats to show that much of this water, originating in the sea between Newfoundland and Greenland, is diverted generally eastward by the time it flows as far south as Massachusetts. From there it disburses to the depths in complex ways that are difficult to follow.
A 50-year-old model of ocean currents had shown this southbound subsurface flow of cold water forming a continuous loop with the familiar northbound flow of warm water on the surface, called the Gulf Stream.
"Everybody always thought this deep flow operated like a conveyor belt, but what we are saying is that concept doesn't hold anymore," said Duke oceanographer Susan Lozier. "So it's going to be more difficult to measure these climate change signals in the deep ocean."
And since cold Labrador seawater is thought to influence and perhaps moderate human-caused climate change, this finding may affect the work of global warming forecasters.
"To learn more about how the cold deep waters spread, we will need to make more measurements in the deep ocean interior, not just close to the coast where we previously thought the cold water was confined," said Woods Hole's Amy Bower.
Lozier, a professor of physical oceanography at Duke's Nicholas School of the Environment and Bower, a senior scientist in the department of physical oceanography at the Woods Hole Institution, are co-principal authors of a report on the findings to be published in the May 14 issue of the research journal Nature.
Their research was supported by the National Science Foundation.
Climatologists pay attention to the Labrador Sea because it is one of the starting points of a global circulation pattern that transports cold northern water south to make the tropics a little cooler and then returns warm water at the surface, via the Gulf Stream, to moderate temperatures of northern Europe.

Since forecasters say effects of global warming are magnified at higher latitudes, that makes the Labrador Sea an added focus of attention. Surface waters there absorb heat-trapping carbon dioxide from the atmosphere. And a substantial amount of that CO2 then gets pulled underwater where it is no longer available to warm Earth's climate.
"We know that a good fraction of the human caused carbon dioxide released since the Industrial revolution is now in the deep North Atlantic" Lozier said. And going along for the ride are also climate-caused water temperature variations originating in the same Labrador Sea location.
The question is how do these climate change signals get spread further south? Oceanographers long thought all this Labrador seawater moved south along what is called the Deep Western Boundary Current (DWBC), which hugs the eastern North American continental shelf all the way to near Florida and then continues further south.
But studies in the 1990s using submersible floats that followed underwater currents "showed little evidence of southbound export of Labrador sea water within the Deep Western Boundary Current (DWBC)," said the new Nature report.
Scientists challenged those earlier studies, however, in part because the floats had to return to the surface to report their positions and observations to satellite receivers. That meant the floats' data could have been "biased by upper ocean currents when they periodically ascended," the report added.
To address those criticisms, Lozier and Bower launched 76 special Range and Fixing of Sound floats into the current south of the Labrador Sea between 2003 and 2006. Those "RAFOS" floats could stay submerged at 700 or 1,500 meters depth and still communicate their data for a range of about 1,000 kilometers using a network of special low frequency and amplitude seismic signals.
But only 8 percent of the RAFOS floats' followed the conveyor belt of the Deep Western Boundary Current, according to the Nature report. About 75 percent of them "escaped" that coast-hugging deep underwater pathway and instead drifted into the open ocean by the time they rounded the southern tail of the Grand Banks.
Eight percent "is a remarkably low number in light of the expectation that the DWBC is the dominant pathway for Labrador Sea Water," the researchers wrote.
Studies led by Lozier and other researchers had previously suggested cold northern waters might follow such "interior pathways" rather than the conveyor belt in route to subtropical regions of the North Atlantic. But "these float tracks offer the first evidence of the dominance of this pathway compared to the DWBC."
Since the RAFOS float paths could only be tracked for two years, Lozier, her graduate student Stefan Gary, and German oceanographer Claus Boning also used a modeling program to simulate the launch and dispersal of more than 7,000 virtual "efloats" from the same starting point.
"That way we could send out many more floats than we can in real life, for a longer period of time," Lozier said.
Subjecting those efloats to the same underwater dynamics as the real ones, the researchers then traced where they moved. "The spread of the model and the RAFOS float trajectories after two years is very similar," they reported.
"The new float observations and simulated float trajectories provide evidence that the southward interior pathway is more important for the transport of Labrador Sea Water through the subtropics than the DWBC, contrary to previous thinking," their report concluded.
"That means it is going to be more difficult to measure climate signals in the deep ocean," Lozier said. "We thought we could just measure them in the Deep Western Boundary Current, but we really can't."
Source: Duke University (news : web)

Changes In The Sun Are Not Causing Global Warming, New Study Shows

2009-05-11T22:37:00.001-07:00

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ScienceDaily (May 12, 2009) — With the U.S. Congress beginning to consider regulations on greenhouse gases, a troubling hypothesis about how the sun may impact global warming is finally laid to rest.

Carnegie Mellon University's Peter Adams along with Jeff Pierce from Dalhousie University in Halifax, Canada, have developed a model to test a controversial hypothesis that says changes in the sun are causing global warming.
The hypothesis they tested was that increased solar activity reduces cloudiness by changing cosmic rays. So, when clouds decrease, more sunlight is let in, causing the earth to warm. Some climate change skeptics have tried to use this hypothesis to suggest that greenhouse gases may not be the global warming culprits that most scientists agree they are.
In research published in Geophysical Research Letters, and highlighted in the May 1 edition of Science, Adams and Pierce report the first atmospheric simulations of changes in atmospheric ions and particle formation resulting from variations in the sun and cosmic rays. They find that changes in the concentration of particles that affect clouds are 100 times too small to affect the climate.
"Until now, proponents of this hypothesis could assert that the sun may be causing global warming because no one had a computer model to really test the claims," said Adams, a professor of civil and environmental engineering at Carnegie Mellon.
"The basic problem with the hypothesis is that solar variations probably change new particle formation rates by less than 30 percent in the atmosphere. Also, these particles are extremely small and need to grow before they can affect clouds. Most do not survive to do so," Adams said.
Despite remaining questions, Adams and Pierce feel confident that this hypothesis should be laid to rest. "No computer simulation of something as complex as the atmosphere will ever be perfect," Adams said. "Proponents of the cosmic ray hypothesis will probably try to question these results, but the effect is so weak in our model that it is hard for us to see this basic result changing."
Journal references:
J. R. Pierce and P. J. Adams. Can cosmic rays affect cloud condensation nuclei by altering new particle formation rates? Geophys. Res. Lett., 2009; (in press) DOI: 10.1029/2009GL037946
Richard A. Kerr. Study Challenges Cosmic Ray-Climate Link. Science, 2009; 324 (5927): 576 DOI: 10.1126/science.324_576b
Adapted from materials provided by Carnegie Mellon University.

As Earth's air slowly trickles away into space, will our planet come to look like Venus?

2009-05-11T08:09:00.001-07:00

SOURCE

By Kevin J. Zahnle and David C. Catling

Many of the gases that make up Earth’s atmosphere and those of the other planets are slowly leaking into space. Hot gases, especially light ones, evaporate away; chemical reactions and particle collisions eject atoms and molecules; and asteroids and comets occasionally blast out chunks of atmosphere.
This leakage explains many of the solar system’s mysteries. For instance, Mars is red because its water vapor got broken down into hydrogen and oxygen, the hydrogen drifted away, and the surplus oxygen oxidized—in essence, rusted—the rocks. A similar process on Venus let carbon dioxide build up into a thick ocean of air; ironically, Venus’s huge atmosphere is the result of the loss of gases.

One of the most remarkable features of the solar system is the variety of planetary atmospheres. Earth and Venus are of comparable size and mass, yet the surface of Venus bakes at 460 degrees Celsius under an ocean of carbon dioxide that bears down with the weight of a kilometer of water. Callisto and Titan—planet-size moons of Jupiter and Saturn, respectively—are nearly the same size, yet Titan has a nitrogen-rich atmosphere thicker than our own, whereas Callisto is essentially airless. What causes such extremes? If we knew, it would help explain why Earth teems with life while its planetary siblings appear to be dead. Knowing how atmospheres evolve is also essential to determining which planets beyond our solar system might be habitable.
A planet can acquire a gaseous cloak in many ways: it can release vapors from its interior, it can capture volatile materials from comets and asteroids when they strike, and its gravity can pull in gases from interplanetary space. But planetary scientists have begun to appreciate that the escape of gases plays as big a role as the supply. Although Earth’s atmosphere may seem as permanent as the rocks, it gradually leaks back into space. The loss rate is currently tiny, only about three kilograms of hydrogen and 50 grams of helium (the two lightest gases) per second, but even that trickle can be significant over geologic time, and the rate was probably once much higher. As Benjamin Franklin wrote, “A small leak can sink a great ship.” The atmospheres of terrestrial planets and outer-planet satellites we see today are like the ruins of medieval castles—remnants of riches that have been subject to histories of plunder and decay. The atmospheres of smaller bodies are more like crude forts, poorly defended and extremely vulnerable.
Recognizing the importance of atmospheric escape changes our perspective on the solar system. For decades, scientists have pondered why Mars has such a thin atmosphere, but now we wonder: Why does it have any atmosphere left at all? Is the difference between Titan and Callisto a consequence of Callisto’s losing its atmosphere, rather than of Titan having been born of airier stuff? Was Titan’s atmosphere once even thicker than it is today? How did Venus steadfastly cling to its nitrogen and carbon dioxide yet thoroughly lose its water? Did escape of hydrogen help to set the stage for complex life on Earth? Will it one day turn our planet into another Venus?
When the Heat Is OnA spaceship that reaches escape velocity is moving fast enough to break free of a planet’s gravity. The same is true of atoms and molecules, although they usually reach escape velocity less purposefully. In thermal escape, gases get too hot to hold on to. In nonthermal processes, chemical or charged-particle reactions hurl out atoms and molecules. And in a third process, asteroid and comet impacts blast away the air.
Thermal escape is, in some ways, the most common and straightforward of the three. All bodies in the solar system are heated by sunlight. They rid themselves of this heat in two ways: by emitting infrared radiation and by shedding matter. In long-lived bodies such as Earth, the former process prevails; for others, such as comets, the latter dominates. Even a body the size of Earth can heat up quickly if absorption and radiation get out of balance, and its atmosphere—which typically has very little mass compared with the rest of the planet—can slough off in a cosmic instant. Our solar system is littered with airless bodies, and thermal escape seems to be a common culprit. Airless bodies stand out as those where solar heating exceeds a certain threshold, which depends on the strength of the body’s gravity [Purchase the digital edition to see related sidebar].
Thermal escape occurs in two ways. In the first, called Jeans escape, after James Jeans, the English astronomer who described it in the early 20th century, air literally evaporates atom by atom, molecule by molecule, off the top of the atmosphere. At lower altitudes, collisions confine particles, but above a certain altitude, known as the exobase, which on Earth is about 500 kilometers above the surface, air is so tenuous that gas particles hardly ever collide. Nothing stops an atom or molecule with sufficient velocity from flying away into space.

As the lightest gas, hydrogen is the one that most easily overcomes a planet’s gravity. But first it must reach the exobase, and on Earth that is a slow process. Hydrogen-bearing molecules tend not to rise above the lowest layer of atmosphere: water vapor (H2O) condenses out and rains back down, and methane (CH4) is oxidized to form carbon dioxide (CO2). Some water and methane molecules reach the stratosphere and decompose, releasing hydrogen, which slowly diffuses upward until it reaches the exobase. A small amount clearly makes it out because ultraviolet images reveal a halo of hydrogen atoms surrounding our planet [Purchase the digital edition to see related sidebar].
The temperature at Earth’s exobase oscillates but is typically about 1,000 kelvins, implying that hydrogen atoms have an average speed of five kilometers per second. That is less than Earth’s escape velocity at that altitude, 10.8 kilometers per second, but the average conceals a wide range, so some hydrogen atoms still manage to break free of our planet’s gravity. This loss of particles from the energetic tail of the speed distribution explains about 10 to 40 percent of Earth’s hydrogen loss today. Jeans escape also partly explains why our moon is airless. Gases released from the lunar surface easily evaporate off into space.
A second type of thermal escape is far more dramatic. Whereas Jeans escape occurs when a gas evaporates molecule by molecule, heated air can also flow en masse. The upper atmosphere can absorb ultraviolet sunlight, warm up and expand, pushing air upward. As the air rises, it accelerates smoothly through the speed of sound and then attains the escape velocity. This form of thermal escape is called hydrodynamic escape or, more evocatively, the planetary wind—the latter by analogy to the solar wind, the stream of charged particles blown from the sun into interplanetary space.
Dust in the WindAtmospheres rich with hydrogen are the most vulnerable to hydrodynamic escape. As hydrogen flows outward, it can pick up and drag along heavier molecules and atoms with it. Much as the desert wind blows dust across an ocean and sand grains from dune to dune, while leaving cobbles and boulders behind, the hydrogen wind carries off molecules and atoms at a rate that diminishes with their weight. Thus, the present composition of an atmosphere can reveal whether this process has ever occurred.
In fact, astronomers have seen the telltale signs of hydrodynamic escape outside the solar system, on the Jupiter-like planet HD 209458b. Using the Hubble Space Telescope, Alfred Vidal-Madjar of the Paris Astrophysics Institute and his colleagues reported in 2003 that the planet has a puffed-up atmosphere of hydrogen. Subsequent measurements discovered carbon and oxygen in this inflated atmosphere. These atoms are too heavy to escape on their own, so they must have been dragged there by hydrogen. Hydrodynamic loss would also explain why astronomers find no large planets much closer to their stars than HD 209458b is. For planets that orbit within three million kilometers or so of their stars (about half the orbital radius of HD 209458b), hydrodynamic escape strips away the entire atmosphere within a few billion years, leaving behind only a scorched remnant.
This evidence for planetary winds lends credence to ideas put forth in the 1980s about hydrodynamic escape from ancient Venus, Earth and Mars. Three clues suggest this process once operated on these worlds. The first concerns noble gases. Were it not for escape, chemically unreactive gases such as neon or argon would remain in an atmosphere indefinitely. The abundances of their different isotopes would be similar to their original values, which in turn are similar to that of the sun, given their common origin in the solar nebula. Yet the abundances differ.
Second, youthful stars are strong sources of ultraviolet light, and our sun was probably no exception. This radiation could have driven hydrodynamic escape.

Third, the early terrestrial planets may have had hydrogen-rich atmospheres. The hydrogen could have come from chemical reactions of water with iron, from nebular gases or from water molecules broken apart by solar ultraviolet radiation. In those primeval days, asteroids and comets hit more frequently, and whenever they smacked into an ocean, they filled the atmosphere with steam. Over thousands of years the steam condensed and rained back onto the surface, but Venus is close enough to the sun that water vapor may have persisted in the atmosphere, where solar radiation could break it down.
Under such conditions, hydrodynamic escape would readily operate. In the 1980s James F. Kasting, now at Pennsylvania State University, showed that hydrodynamic escape on Venus could have carried away an ocean’s worth of hydrogen within a few tens of millions of years [see “How Climate Evolved on the Terrestrial Planets,” by James F. Kasting, Owen B. Toon and James B. Pollack; Scientific American, February 1988]. Kasting and one of us (Zahnle) subsequently showed that escaping hydrogen would have dragged along much of the oxygen but left carbon dioxide behind. Without water to mediate the chemical reactions that turn carbon dioxide into carbonate minerals such as limestone, the carbon dioxide built up in the atmosphere and created the hellish Venus we see today.
To a lesser degree, Mars and Earth, too, appear to have suffered hydrodynamic losses. The telltale signature is a deficit of lighter isotopes, which are more easily lost. In the atmospheres of Earth and Mars, the ratio of neon 20 to neon 22 is 25 percent smaller than the solar ratio. On Mars, argon 36 is similarly depleted relative to argon 38. Even the isotopes of xenon—the heaviest gas in Earth’s atmosphere apart from pollutants—show the imprint of hydrodynamic escape. If hydrodynamic escape were vigorous enough to sweep up xenon, why did it not sweep up everything else in the atmosphere along with it? To solve this puzzle, we may need to construct a different history for xenon than for the other gases now in the atmosphere.
Hydrodynamic escape may have stripped Titan of much of its air, too. When it descended through Titan’s atmosphere in 2005, the European Space Agency’s Huygens probe found that the ratio of nitrogen 14 to nitrogen 15 is 70 percent of that on Earth. That is a huge disparity given that the two isotopes differ only slightly in their tendency to escape. If Titan’s atmosphere started with the same nitrogen isotopic composition as Earth’s, it must have lost a huge amount of nitrogen—several times the substantial amount it currently has—to bring the ratio down to its present value. In short, Titan’s atmosphere might once have been even thicker than it is today, which only heightens its mystery.
Better Escaping through ChemistryOn some planets, including modern Earth, thermal escape is less important than nonthermal escape. In nonthermal escape, chemical reactions or particle-particle collisions catapult atoms to escape velocity. What nonthermal escape mechanisms have in common is that an atom or molecule reaches a very high velocity as the outcome of a single event that takes place above the exobase, so that bumping into something does not thwart the escapee. Many types of nonthermal escape involve ions. Ordinarily these charged particles are tethered to a planet by its magnetic field, either the global (internally generated) magnetic field—if there is one—or the localized fields induced by the passage of the solar wind. But they find ways to slip out.
In one type of event, known as charge exchange, a fast hydrogen ion collides with a neutral hydrogen atom and captures its electron. The result is a fast neutral atom, which is immune to the magnetic field. This process accounts for 60 to 90 percent of the present loss of hydrogen from Earth and most of the hydrogen loss from Venus.

Another way out exploits a weak spot—dare we say a loophole—in the planet’s magnetic trap. Most magnetic field lines loop from one magnetic pole to the other, but the widest field lines are dragged outward by the solar wind and do not loop back; they remain open to interplanetary space. Through this opening, ions can escape. To be sure, the ions must still overcome gravity, and only the lightest ions such as hydrogen and helium make it. The resulting stream of charged particles, called the polar wind (not to be confused with the planetary wind), accounts for 10 to 15 percent of Earth’s hydrogen loss and almost its entire helium leak.
In some cases, these light ions can sweep up heavier ions with them. This process may explain the xenon puzzle: if the polar wind was more vigorous in the past, it could have dragged out xenon ions. One piece of evidence is that krypton does not have the same isotopic pattern as xenon does, even though it is a lighter gas and, all else being equal, ought to be more prone to escape. The difference is that krypton, unlike xenon, resists ionization, so even a strong polar wind would have left it unaffected.
A third nonthermal process known as photochemical escape operates on Mars and possibly on Titan. Oxygen, nitrogen and carbon monoxide molecules drift into the upper atmosphere, where solar radiation ionizes them. When the ionized molecules recombine with electrons or collide with one another, the energy released splits the molecules into atoms with enough speed to escape.
Mars, Titan and Venus lack global magnetic fields, so they are also vulnerable to a fourth nonthermal process known as sputtering. Without a planetary field to shield it, the upper atmosphere of each of these worlds is exposed to the full brunt of the solar wind. The wind picks up ions, which then undergo charge exchange and escape. Mars’s atmosphere is enriched in heavy nitrogen and carbon isotopes, suggesting that it has lost as much as 90 percent of an earlier atmosphere. Sputtering and photochemical escape are the most likely culprits. In 2013 NASA plans to launch the Mars Atmosphere and Volatile EvolutioN (MAVEN) mission to measure escaping ions and neutral atoms and reconstruct the planet’s atmospheric history.
Inescapable ConsequencesBoth thermal and nonthermal escape are like tiny trickles compared with the huge splash when comets or asteroids crash into planets. If projectiles are sufficiently big and fast, they vaporize both themselves and a similar mass of the surface. The ensuing hot gas plume can expand faster than the escape velocity and drive off the overlying air. The larger the impact energy, the wider the cone of atmosphere ejected. For the asteroid that killed off the dinosaurs 65 million years ago, the cone was about 80 degrees wide from the vertical and contained a hundred-thousandth of the atmosphere. An even more energetic impact can carry away the entire atmosphere above a plane that is tangent to the planet.
Another factor determining the width of the cone is the atmospheric density. The thinner the air, the greater the fraction of the atmosphere that gets lost. The implication is gloomy: once a vulnerable atmosphere starts wearing away, impact erosion becomes ever easier until the atmosphere vanishes altogether. Unfortunately, Mars spent its youth in a bad neighborhood near the asteroid belt and, being small, was especially susceptible. Given the expected size distribution of impactors early in a solar system’s history, the planet should have been stripped of its entire atmosphere in less than 100 million years.
The large moons of Jupiter also live in a dangerous neighborhood—namely, deep in the giant planet’s gravitational field, which accelerates incoming asteroids and comets. Impacts would have denuded these moons of any atmospheres they ever had. In contrast, Titan orbits comparatively far from Saturn, where impact velocities are slower and an atmosphere can survive.

In all these ways, escape accounts for much of the diversity of atmospheres, from the lack of air on Callisto and Ganymede to the absence of water on Venus. A more subtle consequence is that escape tends to oxidize planets, because hydrogen is lost more easily than oxygen. Hydrogen escape is the ultimate reason why Mars, Venus and even Earth are red. Most people do not think of Earth as a red planet, but much of the continental crust is red. Soil and vegetation hide this native hue. All three worlds started out the gray-black color of volcanic rock and reddened as the original minerals oxidized to iron oxides (similar to rust). To account for its color, Mars must have lost an ocean of water equivalent to a global layer meters to tens of meters deep.
On Earth, most researchers attribute the accumulation of oxygen 2.4 billion years ago to photosynthetic organisms, but in 2001 we suggested that the escape of hydrogen also played an important role. Microbes break apart water molecules in photosynthesis, and the hydrogen can pass like a baton from organic matter to methane and eventually reach space. The expected amount of hydrogen loss matches the net excess of oxidized material on Earth today.
Escape helps to solve the mystery of why Mars has such a thin atmosphere. Scientists have long hypothesized that chemical reactions among water, carbon dioxide and rock turned the original thick atmosphere into carbonate minerals. The carbonates were never recycled back into carbon dioxide gas because Mars, being so small, cooled quickly and its volcanoes stopped erupting. The trouble with this scenario is that spacecraft have so far found only a single small area on Mars with carbonate rock, and this outcrop probably formed in warm subsurface waters. Moreover, the carbonate theory offers no explanation for why Mars has so little nitrogen or noble gases. Escape provides a better answer. The atmosphere did not get locked away as rock; it dissipated into space.
A nagging problem is that impact erosion ought to have removed Mars’s atmosphere altogether. What stopped it? One answer is simple chance. Large impacts are inherently rare, and their frequency fell off rapidly about 3.8 billion years ago, so Mars may have been spared the final devastating blow. A large impact of an icy asteroid or comet could have deposited more volatiles than subsequent impacts could remove. Alternatively, remnants of Mars’s atmosphere may have survived underground and leaked out after the bombardment had subsided.
Although Earth seems comparatively unscathed by escape, that will change. Today hydrogen escape is limited to a trickle because the principal hydrogen-bearing gas, water vapor, condenses in the lower atmosphere and rains back to the surface. But our sun is slowly brightening at about 10 percent every billion years. That is imperceptibly slow on a human timescale but will be devastating over geologic time. As the sun brightens and our atmosphere warms, the atmosphere will get wetter, and the trickle of hydrogen escape will become a torrent.
This process is expected to become important when the sun is 10 percent brighter—that is, in a billion years—and it will take another billion years or so to desiccate our planet’s oceans. Earth will become a desert planet, with at most a shrunken polar cap and only traces of precious liquid. After another two billion years, the sun will beat down on our planet so mercilessly even the polar oases will fail, the last liquid water will evaporate and the greenhouse effect will grow strong enough to melt rock. Earth will have followed Venus into a barren lifelessness.
This story was originally printed with the title "The Planetary Air Leak"
ABOUT THE AUTHOR(S)Planetary scientist David C. Catling studies the coupled evolution of planetary surfaces and atmospheres. Formerly at the NASA Ames Research Center, he joined the faculty at the University of Washington in 2001. He is a co- investigator for NASAs Phoenix lander, which completed its mission last December. Kevin J. Zahnle has been a research scientist at the NASA Ames center since 1989. Even by the eclectic standards of planetary science, he has an unusually wide range of interests, from planetary interiors to surfaces to atmospheres. In 1996 Zahnle received the NASA Exceptional Achievement Medal for his work on the impact of Comet Shoemaker-Levy 9 into Jupiter.

Tree-Killing Hurricanes Could Contribute To Global Warming

2009-05-10T00:07:00.000-07:00

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ScienceDaily (May 10, 2009) — A first-of-its kind, long-term study of hurricane impact on U.S. trees shows that hurricane damage can diminish a forest’s ability to absorb carbon dioxide, a major contributor to global warming, from the atmosphere. Tulane University researchers from the Department of Ecology and Evolutionary Biology examined the impact of tropical cyclones on U.S. forests from 1851–2000 and found that changes in hurricane frequency might contribute to global warming.

The results will be published in an upcoming issue of the Proceedings of the National Academy of Sciences.
Trees absorb carbon dioxide as they grow, and release it when they die -- either from old age or from trauma, such as hurricanes. The annual amount of carbon dioxide a forest removes from the atmosphere is determined by the ratio of tree growth to tree mortality each year.
When trees are destroyed en masse by hurricanes, not only will there be fewer trees in the forest to absorb greenhouse gases, but forests could eventually become emitters of carbon dioxide, warming the climate. And other studies, notes Tulane ecologist Jeff Chambers, indicate that hurricanes will intensify with a warming climate.
“If landfalling hurricanes become more intense or more frequent in the future, tree mortality and damage exceeding 50 million tons of tree biomass per year would result in a net carbon loss from U.S. forest ecosystems,” says Chambers.
The study, which was led by Tulane postdoctoral research associate Hongcheng Zeng, establishes an important baseline to evaluate changes in the frequency and intensity of future landfalling hurricanes.
Using field measurements, satellite image analyses, and empirical models to evaluate forest and carbon cycle impacts, the researchers established that an average of 97 million trees have been affected each year for the past 150 years over the entire United States, resulting in a 53-million ton annual biomass loss and an average carbon release of 25 million tons. Forest impacts were primarily located in Gulf Coast areas, particularly southern Texas and Louisiana and south Florida, while significant impacts also occurred in eastern North Carolina.
Chambers compares the data from this study to a 2007 study that showed that a single storm – Hurricane Katrina -- destroyed nearly 320 million trees with a total biomass loss equivalent to 50–140 percent of the net annual U.S. carbon sink in forest trees.
“The bottom line,” says Chambers, “is that any sustained increase in hurricane tree biomass loss above 50 million tons would potentially undermine our efforts to reduce human fossil fuel carbon emissions.”
Study contributors include Tulane lab researchers Robinson Negrón-Juárez and David Baker; George Hurtt of the Institute for the Study of Earth, Oceans, and Space at the University of New Hampshire; and Mark Powell at the Hurricane Research Division, National Oceanic and Atmospheric Administration. For more information contact Tulane’s Office of Public Relations.
Adapted from materials provided by Tulane University.

Climate Adds Fuel To Asian Wildfire Emissions

2009-05-10T00:01:00.001-07:00

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ScienceDaily (May 10, 2009) — In the last decade, Asian farmers have cleared tens of thousands of square miles of forests to accommodate the world's growing demand for palm oil, an increasingly popular food ingredient. Ancient peatlands have been drained and lush tropical forests have been cut down.

As a result, the landscape of equatorial Asia now lies vulnerable to fires, which are growing more frequent and having a serious impact on the air as well as the land.
A team of NASA-sponsored researchers have used satellites to make the first series of estimates of carbon dioxide (CO2) emitted from these fires -- both wildfires and fires started by people -- in Malaysia, Indonesia, Borneo, and Papua New Guinea. They are now working to understand how climate influences the spread and intensity of the fires.
Using data from a carbon-detecting NASA satellite and computer models, the researchers found that seasonal fires from 2000 to 2006 doubled the amount of carbon dioxide (CO2) released from the Earth to the atmosphere above the region. The scientists also observed through satellite remote sensing that fires in regional peatlands and forests burned longer and emitted ten times more carbon when rainfall declined by one third the normal amount. The results were presented in December 2008 in Proceedings of the National Academy of Sciences.
Tropical Asian fires first grabbed the attention of government officials, media, and conservationists in 1997, when fires set to clear land for palm oil and rice plantations burned out of control. The fires turned wild and spread to dry, flammable peatlands during one of the region's driest seasons on record. By the time the flames subsided in early 1998, emissions from the fires had reached 40 percent of the global carbon emissions for the period.
"In this region, decision makers are facing a dichotomy of demands, as expanding commercial crop production is competing with efforts to ease the environmental impact of fires," said Jim Collatz, an Earth scientist at NASA's Goddard Space Flight Center in Greenbelt, Md., and a co-author of the study. "The science is telling us that we need strategies to reduce the occurrence of deforestation fires and peatlands wildfires. Without some new strategies, emissions from the region could rise substantially in a drier, warmer future."
Since the 1997 event, the region has been hit by two major dry spells and a steady upswing in fires, threatening biodiversity and air quality and contributing to the buildup of CO2 in the atmosphere. As more CO2 is emitted, the global atmosphere traps more heat near Earth's surface, leading to more drying and more fires.
Until recently, scientists knew little about what drives changes in how fires spread and how long they burn. Collatz, along with lead author Guido van der Werf of Vrije University, Amsterdam, and other colleagues sought to estimate the emissions since the devastating 1997-98 fires and to analyze the interplay between the fires and drought.
They used the carbon monoxide detecting Measurements of Pollution in the Troposphere (MOPITT) instrument on NASA's Terra satellite -- as well as 1997-2006 fire data and research computer models -- to screen for and differentiate between carbon emissions from deforestation versus general emissions. Carbon monoxide is a good indicator of the occurrence of fire, and the amounts of carbon monoxide in fire emissions are related to the amount of carbon dioxide. They also compared the emissions from different types of plant life (peat land vs. typical forest) by examining changes in land cover and land use as viewed by Terra's Moderate Resolution Imaging Spectradiometer (MODIS) and by Landsat 7.
Collatz explained that two climate phenomena drive regional drought. El Niño's warm waters in the Eastern Pacific change weather patterns around the world every few years and cause cooler water temperatures in the western Pacific near equatorial Asia that suppress the convection necessary for rainfall. Previously, scientists have used measurements from NASA's Tropical Rainfall Measurement Mission satellite to correlate rainfall with carbon losses and burned land data, finding that wildfire emissions rose during dry El Niño seasons. The Indian Ocean dipole phenomenon affects climate in the Indian Ocean region with oscillating ocean temperatures characterized by warmer waters merging with colder waters to inhibit rainfall over Indonesia, Borneo, and their neighbors.
"This link between drought and emissions should be of concern to all of us," said co-author Ruth DeFries, an ecologist at Columbia University in New York. "If drought becomes more frequent with climate change, we can expect more fires."
Collatz, DeFries, and their colleagues found that between 2000 and 2006, the average carbon dioxide emissions from equatorial Asia accounted for about 2 percent of global fossil fuel emissions and 3 percent of the global increase in atmospheric CO2. But during moderate El Niño years in 2002 and 2006, when dry season rainfall was half of normal, fire emissions rose by a factor of 10. During the severe El Niño of 1997-1998, fire emissions from this region comprised 15 percent of global fossil fuel emissions and 31 percent of the global atmospheric increase over that period.
"This study not only updates our measurements of carbon losses from these fires, but also highlights an increasingly important factor driving change in equatorial Asia," explained DeFries. "In this part of Asia, human-ignited forest and peat fires are emitting excessive carbon into the atmosphere. In climate-sensitive areas like Borneo, human response to drought is a new dynamic affecting feedbacks between climate and the carbon cycle."
In addition to climate influences, human activities contribute to the growing fire emissions. Palm oil is increasingly grown for use as a cooking oil and biofuel, while also replacing trans fats in processed foods. It has become the most widely produced edible oil in the world, and production has swelled in recent years to surpass that of soybean oil. More than 30 million metric tons of palm oil are produced in Malaysia and Indonesia alone, and the two countries now supply more than 85 percent of global demand.
The environmental effects of such growth have been significant. Land has to be cleared to grow the crop, and the preferred method is fire. The clearing often occurs in drained peatlands that are otherwise swampy forests where the remains of past plant life have been submerged for centuries in as much as 60 feet of water. Peat material in Borneo, for example, stores the equivalent of about nine years worth of global fossil fuel emissions.
"Indonesia has become the third largest greenhouse gas emitter after the United States and China, due primarily to these fire emissions," Collatz said. "With an extended dry season, the peat surface dries out, catches fire, and the lack of rainfall can keep the fires going for months."
Besides emitting carbon, the agricultural fires and related wildfires also ravage delicate ecosystems in conservation hotspots like the western Pacific island of Borneo, home to more than 15,000 species of plants, 240 species of trees, and an abundance of endangered animals.
Smoke and other fire emissions also regularly taint regional air quality to such a degree that officials have to close schools and airports out of concern for public health and safety. Peat fires also aggravate air pollution problems in this region because they release four times more carbon monoxide than forest fires. In 1997, air pollution from the fires cost the region an estimated $4.5 billion in tourism and business.
Adapted from materials provided by NASA/Goddard Space Flight Center.

Measuring Snow With A Bucket, A Windmill, And The Sun? Government Goes Off The Power Grid In Maine

2009-05-09T09:02:00.001-07:00

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ScienceDaily (May 9, 2009) — In Maine, government scientists have figured out how to measure snowfall in remote areas with a bucket, a small windmill, and the sun -- all the while saving money, energy, and, ultimately helping to save lives.

What led to this energy-efficient ingenuity was the need to help the National Weather Service forecast and predict the risk of floods from spring snowmelt.
The problem was this: While the USGS has about 15 snowmelt measurement sites in Maine, they also needed a way to measure snowfall in remote areas where power grids are scarce. Emergency managers need accurate information to prepare for forthcoming hazards and energy companies need to plan ahead for how much water to expect in reservoirs.
"We needed to find an alternative power source," said Bob Lent, chief of the USGS Maine Water Science Center in Augusta. "So we cobbled together a small-scale commercial windmill to replace commercial AC power, and supplemented the windmill with solar panels. What we ended up with is a windmill that powers our measurements on windy and cloudy days, and solar panels that power them on calm, sunny days," said Lent. "And," he added, "not only will we get more accurate information, but the systems will pay for themselves in about 3 to 4 years since using the electricity-dependent devices cost between $200 and $400 a year."
A prototype system has been housed in use at the USGS office in Augusta for the past winter. It has proved so accurate, said Lent, that the USGS plans to install four snowfall sites around the state this summer using the same system.
Basically, the system looks like this: a gage is attached to a 5-gallon bucket that sits atop a simple wooden platform on a metal pole. The gage has a heating element to melt the snow as it collects in the cone of the bucket. The gage only turns on when snow is detected. Nearby is a data-collection box that is linked to the windmill and solar panels. When the bucket fills up with melted snow it tips over and empties. Each tip of the bucket measures 0.01 inches of precipitation and is recorded to the data recorder, which transmits the data and is updated on the web every hour.
"We are very optimistic about the utility of this system in other remote areas in the country and not just for snowfall measurements. It would be good for any remote site that needs more power than solar alone can deliver. For example, this could be used to measure water quality in the swamps of Florida as well as snowfall in Maine," Lent noted.
"It's a very small step in a very long journey of helping this country become greener, but this embodies what we need to be doing and the direction in which we need to be going," said Lent.
Adapted from materials provided by U.S. Geological Survey.

Rise Of Oxygen Caused Earth's Earliest Ice Age

2009-05-08T05:50:00.001-07:00

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ScienceDaily (May 7, 2009) — Geologists may have uncovered the answer to an age-old question - an ice-age-old question, that is. It appears that Earth's earliest ice ages may have been due to the rise of oxygen in Earth's atmosphere, which consumed atmospheric greenhouse gases and chilled the earth.

Alan J. Kaufman, professor of geology at the University of Maryland, Maryland geology colleague James Farquhar, and a team of scientists from Germany, South Africa, Canada, and the U.S.A., uncovered evidence that the oxygenation of Earth's atmosphere - generally known as the Great Oxygenation Event - coincided with the first widespread ice age on the planet.
"We can now put our hands on the rock library that preserves evidence of irreversible atmospheric change," said Kaufman. "This singular event had a profound effect on the climate, and also on life."
Using sulfur isotopes to determine the oxygen content of ~2.3 billion year-old rocks in the Transvaal Supergroup in South Africa, they found evidence of a sudden increase in atmospheric oxygen that broadly coincided with physical evidence of glacial debris, and geochemical evidence of a new world-order for the carbon cycle.
"The sulfur isotope change we recorded coincided with the first known anomaly in the carbon cycle. This may have resulted from the diversification of photosynthetic life that produced the oxygen that changed the atmosphere," Kaufman said.
Two and a half billion years ago, before the Earth's atmosphere contained appreciable oxygen, photosynthetic bacteria gave off oxygen that first likely oxygenated the surface of the ocean, and only later the atmosphere. The first formed oxygen reacted with iron in the oceans, creating iron oxides that settled to the ocean floor in sediments called banded iron-formations - layered deposits of red-brown rock that accumulated in ocean basins around the worldwide. Later, once the iron was used up, oxygen escaped from the oceans and started filling up the atmosphere.
Once oxygen made it into the atmosphere, Kaufman's team suggests that it reacted with methane, a powerful greenhouse gas, to form carbon dioxide, which is 62 times less effective at warming the surface of the planet. "With less warming potential, surface temperatures may have plummeted, resulting in globe-encompassing glaciers and sea ice" said Kaufman.
In addition to its affect on climate, the rise in oxygen stimulated the rise in stratospheric ozone, our global sunscreen. This gas layer, which lies between 12 and 30 miles above the surface, decreased the amount of damaging ultraviolet sunrays reaching the oceans, allowing photosynthetic organisms that previously lived deeper down, to move up to the surface, and hence increase their output of oxygen, further building up stratospheric ozone.
"New oxygen in the atmosphere would also have stimulated weathering processes, delivering more nutrients to the seas, and may have also pushed biological evolution towards eukaryotes, which require free oxygen for important biosynthetic pathways," said Kaufman.
The result of the Great Oxidation Event, according to Kaufman and his colleagues, was a complete transformation of Earth's atmosphere, of its climate, and of the life that populated its surface. The study is published in the May issue of Geology.
Adapted from materials provided by University of Maryland.

World's Most Unusual Volcano: Origin Of Carbon-based Lavas Revealed

2009-05-08T01:02:00.001-07:00

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ScienceDaily (May 7, 2009) — Scientists studying the world's most unusual volcano have discovered the reason behind its unique carbon-based lavas. The new geochemical analyses reveals that an extremely small degree of partial melting of typical minerals in the earth's upper mantle is the source of the rare carbon-derived lava erupting from Tanzania's Oldoinyo Lengai volcano.

Although carbon-based lavas, known as carbonatites, are found throughout history, the Oldoinyo Lengai volcano, located in the East African Rift in northern Tanzania, is the only place on Earth where they are actively erupting. The lava expelled from the volcano is highly unusual in that it contains almost no silica and greater than 50 percent carbonate minerals. Typically lavas contain high levels of silica, which increases their melting point to above 900°C (1652°F). The lavas of Oldoinyo Lengai volcano erupt as a liquid at approximately 540°C (1004°F). This low silica content gives rise to the extremely fluid lavas, which resembles motor oil when they flow.
A team of scientists from University of New Mexico, Scripps Institution of Oceanography at UC San Diego and Centre de Recherches Petrographiques et Geochimiques in Nancy, France, report new findings of volcanic gas emissions in a paper published in the May 7 issue of the journal Nature.
"The chemistry and isotopic composition of the gases reveal that the CO2 is directly sourced from the upper mantle below the East African Rift," said David Hilton, professor of geochemistry at Scripps Institution of Oceanography at UC San Diego and coauthor of the paper. "These mantle gases allow us to infer the carbon content of the upper mantle that is producing the carbonatites to be around 300 parts per million, a concentration that is virtually identical to that measured below mid-ocean ridges."
Mid-ocean ridges are underwater mountain ranges where the seafloor is spreading due to tectonic plates moving away from one another. Rift valleys, such as the one where Oldoinyo Lengai volcano is located, and mid-ocean ridges are considered to be distinct tectonic regions. However, this study has shown that their chemistries are identical, which led the scientists to suggest that the carbon contents of their mantle sources were not different but due to partial melting of typical minerals located in the earth's mantle.
"Since the volcano was under magma pressure during the eruption, we were able to collect pristine samples of the volcanic gases, with minimal air contamination," said Tobias Fischer, volcanologist at the University of New Mexico. The pristine samples collected during a 2005 eruption offered the scientists a deeper look at the processes taking place in the earth's upper mantle.
The geochemical analyses, some of which were conducted at Hilton's geochemical lab at Scripps Oceanography, revealed that magma from the upper mantle below both the oceans and continents is a uniform and well-mixed reservoir of "typical" volcanic gases such as carbon dioxide, nitrogen, argon and helium.
The lava expelled from the volcano is highly unusual in that it contains almost no silica and greater than 50 percent carbonate minerals. Typically lavas contain high levels of silica, which increases their melting point to above 900°C (1652°F). The lavas of Oldoinyo Lengai volcano are comprised of carbonatites, which erupts as a liquid at approximately 540°C (1004°F). This low silica content gives rise to the extremely fluid lavas, which resembles motor oil when they flow.
"These finding are significant because it shows that these extremely bizarre lavas and their parent magmas, nephelinites, were produced by melting of a typical upper mantle mineral assemblage without an extreme carbon content in the magma source," said geochemist Bernard Marty at the Centre de Recherches Petrographiques et Geochimiques in Nancy, France. "Rather, in order to make carbonatite lavas, all you need is a very low melt fraction of 0.3 percent or less."
Oldoinyo Lengai, like all volcanoes, emits carbon dioxide into the atmosphere as a gas. However, Lengai's magma is unusual in that it also contains high sodium contents. About one percent of the mantle-derived carbon emitted from Lengai goes into the carbonatite melt with the remainder being emitted into the atmosphere as CO2 gas. The CO2 released into the atmosphere by volcanoes worldwide is a small fraction when compared to man-made emissions.
Journal reference:
Fischer et al. Upper-mantle volatile chemistry at Oldoinyo Lengai volcano and the origin of carbonatites. Nature, 2009; 459 (7243): 77 DOI: 10.1038/nature07977
Adapted from materials provided by University of California - San Diego, via EurekAlert!, a service of AAAS.

How Much Oil Have We Used?

2009-05-08T00:33:00.001-07:00

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ScienceDaily (May 8, 2009) — Estimates of how much crude oil we have extracted from the planet vary wildly. Now, UK researchers have published a new estimate in the International Journal of Oil, Gas and Coal Technology that suggests we may have used more than we think.

The idea that we are running out of oil is not a new one, but do we even know how much oil we have extracted from since the first commercial oil wells were sunk in the middle of the nineteenth century? In 2008, chemists Istvan Lakatos and Julianna Lakatos-Szabo of the Hungarian Academy of Sciences theorised that less than 100 billion tonne of crude oil has been produced since 1850 and that the average annual production rate is less than 700 million barrels per year.
They compared proven reserves and estimates of yet-to-find (YTF) resources and echoed the sentiment that we will soon face oil shortages even though a substantial part of those reserves remain in the ground untapped.
Now, John Jones in the School of Engineering, at the University of Aberdeen, UK, suggests that the figures cited by Istvan Lakatos and Julianna Lakatos-Szabo for which they give no references grossly underestimates how much oil we have used already. Jones says that we have used at least 135 billion barrels of oil since 1870, the period during which J.D. Rockefeller established The Standard Oil Company and began drilling in earnest.
The oil industry now spans several generations, says Jones, and has historically been as uninterested in how much oil has been drawn as were economists, day-to-day and annual figures being of much greater concern. However, in 2005, The Oil Depletion Analysis Centre (ODAC) in London provided a total figure of almost 1 trillion barrels of crude oil (944 billion barrels) since commercial drilling began. Even that figure does not add up, Jones explains.
He has calculated a better estimate by using the volume of a barrel (42 US gallons, or 0.16 cubic metres) and a crude oil density of 0.9 tonnes per cubic metre. ODAC's 944 billion barrels is thus the equivalent of 135 billion tonnes.
Jones explains that this figure is of the same order of magnitude as the estimate offered by Lakatos and Lakatos-Szabo, but is nevertheless 35% higher than ODAC's figure. "Their assertion that less than 100 billion tonnes has been produced is significantly inconsistent with the ODAC," says Jones. The implication is that either ODAC or the Hungarian team are incorrect in their estimates, and suggests that clarification of this important figure is now needed.
Journal references:
Jones et al. Total amounts of oil produced over the history of the industry. International Journal of Oil Gas and Coal Technology, 2009; 2 (2): 199 DOI: 10.1504/IJOGCT.2009.024887
Lakatos et al. Global oil demand and role of chemical EOR methods in the 21st century. International Journal of Oil Gas and Coal Technology, 2008; 1 (1/2): 46 DOI: 10.1504/IJOGCT.2008.016731
Adapted from materials provided by Inderscience, via AlphaGalileo.

Sea Salt Holds Clues To Climate Change

2009-05-07T01:46:00.001-07:00

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ScienceDaily (May 7, 2009) — We know that average sea levels have risen over the past century, and that global warming is to blame. But what is climate change doing to the saltiness, or salinity, of our oceans? This is an important question because big shifts in salinity could be a warning that more severe droughts and floods are on their way, or even that global warming is speeding up.

Now, new research coming out of the United Kingdom (U.K.) suggests that the amount of salt in seawater is varying in direct response to man-made climate change. Working with colleagues to sift through data collected over the past 50 years, Peter Stott, head of climate monitoring and attribution at the Met Office in Exeter, England, studied whether or not human-induced climate change could be responsible for rises in salinity that have been recorded in the subtropical regions of the Atlantic Ocean, areas at latitudes immediately north and south of Earth’s tropics.
By comparing the data to climate models that correct for naturally occurring salinity variations in the ocean, Stott has found that man-made global warming -- over and above any possible natural sources of global warming, such as carbon dioxide given off by volcanoes or increases in the heat output of the sun -- may be responsible for making parts of the North Atlantic Ocean more salty.
Salinity levels are important for two reasons. First, along with temperature, they directly affect seawater density (salty water is denser than freshwater) and therefore the circulation of ocean currents from the tropics to the poles. These currents control how heat is carried within the oceans and ultimately regulate the world’s climate. Second, sea surface salinity is intimately linked to Earth’s overall water cycle and to how much freshwater leaves and enters the oceans through evaporation and precipitation. Measuring salinity is one way to probe the water cycle in greater detail.
In the last half-century or so, the subtropical Atlantic has been getting gradually saltier -- a less than 1 percent increase in real terms, but an effect that is nevertheless significant. “It might sound like quite a small change,” says Stott, “but the overall salinity of our oceans is naturally relatively steady, so it’s actually a lot of freshwater being factored out of the ocean.”
Stott’s analysis suggests that global warming is changing precipitation patterns over our planet. Higher temperatures increase evaporation in subtropical zones; the moisture is then carried by the atmosphere towards higher latitudes (towards the poles), and by trade winds across Central America to the Pacific, where it provides more precipitation. This process concentrates the salt in the water left behind in the North Atlantic, causing salinity to increase.
Water bearer
These are just the sort of effects that Gary Lagerloef and Amit Sen hope to uncover over the next few years. Lagerloef and Sen are, respectively, principal investigator and project manager of Aquarius, part of a brand new satellite mission due to be launched into orbit in May 2010. Aquarius is the first NASA instrument designed to track sea salinity from space and will be the primary payload on the SAC-D spacecraft, which has been built by the Argentinian Space Agency or Comision Nacional de Actividades Espaciales (CONAE). The three-year mission is named after the “cup-bearer to the gods” in Greek mythology.
Sea saltiness has been measured for centuries. Most of the data we have today consist of direct measurements taken at sea (traditionally by ships and, nowadays, more often by automated buoys and profiling floats). But there are vast areas of the ocean surface -- a quarter in total -- where salinity has never been measured. By covering the entire globe once every seven days, Aquarius will fill in the blanks and provide an unprecedented global picture of salinity.
Scientists measure salt levels using a practical salinity scale. One practical salinity unit or psu almost exactly represents the number of grams of salt in a kilogram of seawater. Salinities in the open ocean, free of ice or land mass, generally lie between 32 and 37 psu (the Pacific and Atlantic Oceans have maximum surface salinities around 35 and 37 respectively). “With our instruments we will be able to measure salinity to an accuracy of 0.2 psu,” explains Sen, who works at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif. “If you take half a gallon of water and put a pinch of salt in it, that’s about 0.2 psu. We will be able to detect that from space, while flying about 650 kilometers [about 404 miles] above Earth.”
This is no mean feat and is possible because of some impressive radiometer technology that will fly on board the spacecraft. A radiometer is essentially a sensitive radio receiver, which, in this instance, detects microwave radiation given off by the sea surface. The radiated power of the microwaves that are emitted enables scientists to calculate the saltiness of the water at the surface.
What’s special about the three radiometers designed for Aquarius is their calibration stability -- over a seven-day period, their temperature cannot stray more than 0.1 kelvin (0.18 degrees Fahrenheit). This calls for very precise thermal control and is the reason Aquarius will be able to measure salinity with unprecedented precision.
Boom boom
“We measure salinity in the top one to three centimeters of water because that is the crucial layer that connects the atmosphere and the oceans,” explains Simon Collins, instrument manager for Aquarius who is also based at JPL. “As such, one of the largest errors in our measurement comes from ripples in the surface of the sea.” To correct for this, Aquarius also carries with it a scatterometer -- a state-of-the-art radar instrument that senses roughness in the sea surface by booming microwave pulses down to the ocean and detecting the scattered pulses bounced back to the satellite.
While Aquarius has not yet set off, it has been a long journey for the project’s scientists and engineers, who are now ready to ship their instrument from JPL to Argentina. There it will be installed on the SAC-D spacecraft, before being transported to Brazil for functional and environmental testing and returned to the United States in April 2010, ready for its trip to space.
“People don’t realize that there is so much water and so little land,” Sen remarks. Aquarius, flying high above us, will shed light on El Niño and La Niña, phases of the world’s most powerful climate phenomena, reveal insights into how monsoons develop and, most importantly of all, how a pinch of salt can change our lives.
Journal references:
R. Curry, B. Dickson & I. Yashayaev. A change in the freshwater balance of the Atlantic Ocean over the past four decades. Nature, 2003; 426 (6968): 826 DOI: 10.1038/nature02206
P. A. Stott, R. T. Sutton & D. M. Smith. Detection and attribution of Atlantic salinity changes. Geophysical Research Letters, 2008; 35 (21): L21702 DOI: 10.1029/2008GL035874
Adapted from materials provided by NASA/Jet Propulsion Laboratory. Original article written by Amber Jenkins.

Erupting Undersea Volcano Near Island Of Guam Supports Unique Ecosystem

2009-05-06T09:18:00.000-07:00

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ScienceDaily (May 5, 2009) — Scientists who have just returned from an expedition to an erupting undersea volcano near the Island of Guam report that the volcano appears to be continuously active, has grown considerably in size during the past three years, and its activity supports a unique biological community thriving despite the eruptions.

An international science team on the expedition captured dramatic new information about the eruptive activity of NW Rota-1.
"This research allows us, for the first time, to study undersea volcanoes in detail and close up," said Barbara Ransom, program director in NSF's Division of Ocean Sciences, which funded the research. "NW Rota-1 remains the only place on Earth where a deep submarine volcano has ever been directly observed while erupting."
Scientists first observed eruptions at NW Rota-1 in 2004 and again in 2006, said Bill Chadwick, an Oregon State University (OSU) volcanologist and chief investigator on the expedition. This time, however, they discovered that the volcano had built a new cone 40 meters high and 300 meters wide.
"That's as tall as a 12-story building and as wide as a full city block," Chadwick said. "As the cone has grown, we've seen a significant increase in the population of animals that lives atop the volcano. We're trying to determine if there is a direct connection between the increase in the volcanic activity and that population increase."
Animals in this unusual ecosystem include shrimp, crab, limpets and barnacles, some of which are new species.
"They're specially adapted to their environment," said Chadwick, "and are thriving in harsh chemical conditions that would be toxic to normal marine life.
"Life here is actually nourished by the erupting volcano."
Verena Tunnicliffe, a biologist from the University of Victoria, said that most of the animals are dependent on diffuse hydrothermal venting that provides basic food in the form of bacterial filaments coating the rocks.
"It appears that since 2006 the diffuse venting has spread and, with it, the vent animals," Tunnicliffe said. "There is now a very large biomass of shrimp on the volcano, and two species are able to cope with the volcanic conditions."
The shrimp reveal intriguing adaptations to volcano living.
"The 'Loihi' shrimp has adapted to grazing the bacterial filaments with tiny claws like garden shears," said Tunnicliffe. "The second shrimp is a new species--they also graze as juveniles, but as they grow to adult stage, their front claws enlarge and they become predators."
The Loihi shrimp was previously known only from a small active volcano near Hawaii--a long distance away. It survives on the fast-growing bacteria and tries to avoid the hazards of the volcanic eruptions. Clouds of these shrimp were seen fleeing volcanic bursts.
The other species attacks the Loihi shrimp and preys on marine life that wanders too close to the volcanic plumes and dies. "We saw dying fish, squid, etc., raining down onto the seamount, where they were jumped on by the volcano shrimp--a lovely adaptation to exploiting the noxious effects of the volcano," Tunnicliffe said.
The new studies are important because NW Rota-1 provides a one-of-a-kind natural laboratory for the investigation of undersea volcanic activity and its relation to chemical-based ecosystems at hydrothermal vents, where life on Earth may have originated.
"It is unusual for a volcano to be continuously active, even on land," Chadwick pointed out.
"This presents us with a fantastic opportunity to learn about processes we've never been able to directly observe before," he said. "When volcanoes erupt in shallow water they can be extremely hazardous, creating huge explosions and even tsunamis. But here, we can safely observe an eruption in the deep ocean and learn valuable lessons about how lot lava and seawater interact."
Chadwick said that volcanic plumes behave completely differently underwater than on land, where the eruption cloud is filled with steam and ash, and other gases are invisible.
"In the ocean, any steam immediately condenses and disappears and what is visible are clear bubbles of carbon dioxide and a dense cloud made of tiny droplets of molten sulfur, formed when sulfur dioxide mixes with seawater," Chadwick said. "These volcanic gases make the eruption cloud extremely acidic--worse than stomach acid--which is another challenge for biological communities living nearby."
Ocean acidification is a serious concern because of human-induced carbon dioxide accumulating in the atmosphere. "Submarine volcanoes are places where we can study how animals have adapted to very acidic conditions," Chadwick said.
During the April 2009 expedition, aboard the University of Washington's R/V Thompson, the scientists made dives with Jason, a remotely operated vehicle (ROV) operated by the Woods Hole Oceanographic Institution.
Chadwick said that "it was amazing how close Jason can get to the eruptive vent because the pressure at a depth of 520 meters [about 1,700 feet] in the ocean keeps the energy released from the volcano from becoming too explosive." Some of the most intriguing observations came when the volcano slowly pushed lava up and out of the erupting vent.
"As this was happening, the ground in front of us shuddered and quaked, and huge blocks were bulldozed out of the way to make room for new lava emerging from the vent," Chadwick said.
Part of the evidence that the volcano is in a constant state of eruption comes from an underwater microphone--or hydrophone--that was deployed a year ago at NW Rota-1 by OSU geologist Bob Dziak.
The hydrophone "listened" for the sounds of volcanic activity. The data it recorded clearly show that the volcano was active the entire year before the latest expedition. Another hydrophone and other instruments will monitor the volcano in the coming year.
The international team included scientists from OSU, the University of Washington, University of Victoria, University of Oregon, NOAA's Pacific Marine Environmental Laboratory, New Zealand and Japan.
This research was funded by the National Science Foundation (NSF).
Adapted from materials provided by National Science Foundation.

New Antarctic Seabed Sonar Images Reveal Clues To Sea-level Rise

2009-05-06T09:11:00.001-07:00

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ScienceDaily (May 6, 2009) — Motorway-sized troughs and channels carved into Antarctica's continental shelves by glaciers thousands of years ago could help scientists to predict future sea-level rise, according to a report in the May issue of the journal Geology.

Using sonar technology from onboard ships, scientists from British Antarctic Survey (BAS) and the German Alfred Wegener Institute (AWI) captured the most extensive, continuous set of images of the seafloor around the Amundsen Sea embayment ever taken. This region is a major drain point of the West Antarctic Ice Sheet (WAIS) and considered by some scientists to be the most likely site for the initiation of major ice sheet collapse.
The sonar images reveal an 'imprint' of the Antarctic ice sheet as it was at the end of the last ice age around 10 thousand years ago. The extent of ice covering the continent was much larger than it is today. The seabed troughs and channels that are now exposed provide new clues about the speed and flow of the ice sheet. They indicate that the controlling mechanisms that move ice towards the coast and into the sea are more complex than previously thought.
Lead author Rob Larter from British Antarctic Survey said, "One of the greatest uncertainties for predicting future sea-level rise is Antarctica's likely contribution. It is very important for scientists and our society to understand fully how polar ice flows into the sea. Indeed, this issue was highlighted in 2007 by the Intergovernmental Panel on Climate Change (IPCC). Our research tells us more about how the ice sheet responded to warming at the end of the last ice age, and how processes at the ice sheet bed controlled its flow. This is a big step toward understanding of how the ice sheets are likely to respond to future warming.'
Background
The area of the Amundsen Sea embayment surveyed was 9950 km2. In the western Amundsen Sea embayment three 17-39 km wide troughs extend seaward from the modern ice shelf front. This is roughly with width of the English Channel. Individual streamlined features carved into the seabed are about as wide as a motorway.
Ice sheet
The Antarctic ice sheet retreated to near its present limit around 10 thousand years ago. It is the layer of ice up to 5000 m thick covering the Antarctic continent. It is formed from snow falling in the interior of the Antarctic which compacts into ice. The ice sheet slowly moves towards the coast, eventually breaking away as icebergs which gradually melt into the sea.
The ice sheet covering East Antarctica is very stable, because it lies on rock that is above sea level and is thought unlikely to collapse. The West Antarctic is less stable, because it sits on rock below sea level.
Ice shelf
An ice shelf is a thick (100-1000 m), floating platform of ice that forms where a glacier or ice sheet flows down to a coastline and onto the ocean surface. Ice shelves are found in Antarctica, Greenland and Canada only.
Glacier
Just as rivers collect water and allow it to flow downhill a glacier is actually a "river" of ice. A glacier flows much more slowly than river. Rivers of ice within ice sheets account for most of the drainage into the oceans.
Continental shelf
The relatively shallow (generally up to 200 meters) seabed surrounding a continent where the depth gradually increases before it plunges into the deep ocean. Around Antarctica the continental shelf is up to 1600 m deep as a result of millions of years of glacial erosion. The deepest parts of the Antarctic continental shelf are near the present ice margin and depths generally decrease offshore.
Journal reference:
Larter et al. Subglacial bedforms reveal complex basal regime in a zone of paleo-ice stream convergence, Amundsen Sea embayment, West Antarctica. Geology, 2009; 37 (5): 411 DOI: 10.1130/G25505A.1
Adapted from materials provided by British Antarctic Survey.

Carbon Dioxide In Atmosphere Can Now Be Measured From Space

2009-04-12T23:46:00.001-07:00

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ScienceDaily (Apr. 12, 2009) — INESC Porto developed a technology, together with ESA – European Space Agency, that enables a more effective measurement of gases in the atmosphere comparatively to the currently used techniques. With this technology, it will be possible to measure gases, such as carbon dioxide, methane, nitrous oxide and ozone – the gases responsible for global warming and greenhouse effects.

The system developed by INESC Porto’s Optoelectronics and Electronic System Unit (UOSE) has a high potential of applicability in satellites due to its efficiency, compactness and reduced volume and mass. The satellites equipped with INESC Porto’s optical fibre filters will be able to detect pollutant gases in the Earth’s atmosphere in concentrations less than 1 km high, at an altitude of 400 km.
The partnership between INESC Porto and ESA started in 2006 and is now showing its first signs of success with the development of an optical fibre filter that is capable of measuring carbon dioxide levels from space.
Other than carbon dioxide, this technology is capable of providing a precise measurement of other pollutant gases, such as methane gas, nitrous oxide and ozone, besides measuring levels of humidity, atmospheric pressure, temperature and wind speed. Thus, this is an essential tool made in Portugal for research on climate change, a step forward to the control of greenhouse gases in the battle against global warming.
If it is applied to satellites, the filter developed by INESC Porto is capable of monitoring all kinds of pollutant gas concentrations less than 1 km high, 50 km wide, at an altitude of 400 km. Unlike what the currently used technologies - atmospheric balloons and airplanes equipped for that purpose -provide, with the filters created by INESC Porto, it will be possible to map the atmosphere three-dimensionally, with a higher resolution and from a single position.
The technology's potential of application in orbital systems and scientific missions has to do with its unique features: efficiency, compactness and reduced volume and mass. The technology developed by INESC Porto consists of an ultra-narrow spectral tuneable and heat-reflecting filter based on optical fibre technology that can be used in order to monitor the atmosphere with the reflection of laser impulses. Using the radiation's time of flight and absorption, it will be possible to extract profiles of pollutant gas concentrations in the atmosphere.
Adapted from materials provided by INESC PORTO.

Potential To Amass More Carbon In Eastern North American Forests

2009-04-11T08:22:00.001-07:00

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ScienceDaily (Apr. 11, 2009) — With climate change looming, the hunt for places that can soak up carbon dioxide from the atmosphere is on.

Obvious "sinks" for the greenhouse gas include the oceans and the enormous trees of tropical rainforests. But temperate forests also play a role, and new research now suggests they can store more carbon than previously thought.
In a study that drew on both historical and present-day datasets, Jeanine Rhemtulla of McGill University and David Mladenoff and Murray Clayton of University of Wisconsin-Madison quantified and compared the above-ground carbon held in the forest trees of Wisconsin just prior to European settlement and widespread logging, and the total carbon they contain today.
Writing in the current issue of the Proceedings of the National Academy of Sciences, the researchers report that despite decades of forest recovery, Wisconsin's woodlands still only hold about two-thirds the carbon of pre-settlement times — suggesting substantial room for them to accumulate more.
"There's probably more potential (to store carbon) than people were considering," says Mladenoff. "There's still a big difference between what was once there and what's there now."
He adds that the true storage potential is probably at least two-fold higher than what he and Rhemtulla calculated, since they factored in only the live, above-ground biomass of tree trunks and crowns, and not the carbon stored in roots and soil.
The results have implications not only for Wisconsin, but also for regions across eastern North America where forests were leveled historically to make room for agriculture, and then grew up again as settlers abandoned their farms and headed west. In Wisconsin, for example, forest biomass and carbon have been steadily recovering since the peak of agricultural clearing in the 1930s, while those in the northeastern U.S. have been rebounding for about 125 years.
Yet, it's precisely because many temperate forests have been recovering for so long that people tend to assume their potential as carbon sinks is "maxed out," says Mladenoff.
"Our results suggest we need to rethink this," he says. "Rather than there being an intrinsic limit on how much carbon a forest can store, how we use the forest — how much we log, how we manage — may be more important."
The findings come amid sweeping discussions of international carbon treaties and accounting systems that are designed to reduce CO2 emissions and combat climate change. In the future, for instance, countries might earn credits for maintaining carbon-rich old-growth forests, or replanting trees on lands logged off previously for agriculture.
Areas that once supported large amounts of forest biomass might also be good sites for growing plantations of hybrid poplar and other biofuels crops, says Mladenoff. But, he cautions, any move toward planting more land in trees must be weighed against competing social and economic factors, such as the need for farmland.
"The landscape is full," says Mladenoff. "So if we're going to add something like forests, we're going to need to take something out."
That certainly seems to be true in Wisconsin. Based on historic carbon levels, the researchers' analysis found that much of the best land for growing trees is the north-central region and along northern Lake Michigan. If those lands could be reforested to pre-settlement levels, the scientists estimate they could add 150 teragrams of carbon (150 million metric tons) to the state's current total of approximately 275 teragrams.
The problem, however, is that most of those lands are still being farmed, setting up an interesting dilemma for policy makers: how to weigh the current economic benefit of agriculture against the future environmental benefit of carbon storage.
"Because we often forget the invisible services, like climate regulation, that ecosystems provide to us for free, we don't usually factor them into our decision making," says Rhemtulla. "But this will need to change if we're going to find ways to meet our immediate needs without compromising critical services over the long term."
Journal reference:
Jeanine M. Rhemtulla, David J. Mladenoff, and Murray K. Clayton. Historical forest baselines reveal potential for continued carbon sequestration. Proceedings of the National Academy of Sciences, 2009; DOI: 10.1073/pnas.0810076106
Adapted from materials provided by University of Wisconsin-Madison.

New Link Between The Evolution Of Complex Life Forms On Earth And Nickel And Methane Gas

2009-04-10T11:38:00.001-07:00

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ScienceDaily (Apr. 9, 2009) — The Earth's original atmosphere held very little oxygen. This began to change around 2.4 billion years ago when oxygen levels increased dramatically during what scientists call the "Great Oxidation Event." The cause of this event has puzzled scientists, but researchers writing in Nature have found indications in ancient sedimentary rocks that it may have been linked to a drop in the level of dissolved nickel in seawater.

"The Great Oxidation Event is what irreversibly changed surface environments on Earth and ultimately made advanced life possible," says research team member Dominic Papineau of the Carnegie Institution's Geophysical Laboratory. "It was a major turning point in the evolution of our planet, and we are getting closer to understanding how it occurred."
The researchers, led by Kurt Konhauser of the University of Alberta in Edmonton, analyzed the trace element composition of sedimentary rocks known as banded-iron formations, or BIFs, from dozens of different localities around the world, ranging in age from 3,800 to 550 million years. Banded iron formations are unique, water-laid deposits often found in extremely old rock strata that formed before the atmosphere or oceans contained abundant oxygen. As their name implies, they are made of alternating bands of iron and silicate minerals. They also contain minor amounts of nickel and other trace elements.
Nickel exists in today's oceans in trace amounts, but was up to 400 times more abundant in the Earth's primordial oceans. Methane-producing microorganisms, called methanogens, thrive in such environments, and the methane they released to the atmosphere might have prevented the buildup of oxygen gas, which would have reacted with the methane to produce carbon dioxide and water. A drop in nickel concentration would have led to a "nickel famine" for the methanogens, who rely on nickel-based enzymes for key metabolic processes. Algae and other organisms that release oxygen during photosynthesis use different enzymes, and so would have been less affected by the nickel famine. As a result, atmospheric methane would have declined, and the conditions for the rise of oxygen would have been set in place.
The researchers found that nickel levels in the BIFs began dropping around 2.7 billion years ago and by 2.5 billion years ago was about half its earlier value. "The timing fits very well. The drop in nickel could have set the stage for the Great Oxidation Event," says Papineau. "And from what we know about living methanogens, lower levels of nickel would have severely cut back methane production."
What caused the drop in nickel? The researchers point to geologic changes that were occurring during the interval. During earlier phases of the Earth's history, while its mantle was extremely hot, lavas from volcanic eruptions would have been relatively high in nickel. Erosion would have washed the nickel into the sea, keeping levels high. But as the mantle cooled, and the chemistry of lavas changed, volcanoes spewed out less nickel, and less would have found its way to the sea.
"The nickel connection was not something anyone had considered before," says Papineau. "It's just a trace element in seawater, but our study indicates that it may have had a huge impact on the Earth's environment and on the history of life."
Dominic Papineau's research is supported by the NASA Exobiology and Evolutionary Biology Program and from the Fond québécois de la recherche sur la nature et les technologies.
Journal reference:
Konhauser et al. Oceanic nickel depletion and a methanogen famine before the Great Oxidation Event. Nature, 2009; 458 (7239): 750 DOI: 10.1038/nature07858
Adapted from materials provided by Carnegie Institution.

Satellite Snow Maps Help Reindeer Herders Adapt To A Changing Arctic

2009-04-10T11:22:00.001-07:00

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ScienceDaily (Apr. 10, 2009) — Arctic reindeer herders are facing the challenges of adapting to climate change as a warmer Arctic climate makes it harder for herds to find food and navigate. To help them adapt, the ESA-backed Polar View initiative is providing them with satellite-based snow maps.

"Snow is of paramount importance for reindeer herding because its quality determines whether reindeer are able to access the pastures that lie beneath it for much of the year," said Anders Oskal, the Director of the International Centre for Reindeer Husbandry (ICR). "Detailed circumpolar snow information is, thus, becoming increasingly important following the recent changes in the Arctic climate."
Oskal is working with Sámi reindeer herders in Finnmark, Norway, to help them maintain and develop sustainable reindeer husbandry. According to him, Finnmark is the area of Norway that is predicted to experience the largest temperature increases, raising concerns about whether ice layers will form over pastures preventing reindeer from foraging.
For this reason, ICR partnered with Polar View to examine how satellite observations could help by gathering information on snow and snow change in a timely and accurate manner for such vast circumpolar regions. Under the Polar View initiative, Kongsberg Satellite Services (KSAT) have been providing snow melt maps for Norway and Sweden and Eurasia snow cover maps for the last 18 months.
"The experience so far has definitely been positive, and the reindeer herders are extremely interested in the future utilisation of Polar View products that can relate important information about local snow conditions," Oskal said. "These products could have important consequences for herders’ decisions regarding winter pasture quality and potential migration routes."
In addition to climate change, reindeer herders also have to face a loss of pastures due to infrastructure development, such as roads, hydroelectric power dams and cabin resorts. In the future, ICR and Polar View may partner again to monitor the different forms of land use change over time.
Products from Polar View have also been used as input for an International Polar Year Project – IPY EALÁT-Network Study – on reindeer herding and adaptation to climate change.
The two Polar View snow services are provided by KSAT in partnership with the Northern Research Institute, the Norwegian Computing Centre and the Finnish Meteorological Institute.
Polar View is supported by ESA and the European Commission (EC) with participation from the Canadian Space Agency. It was established under the Global Monitoring for Environment and Security (GMES) programme – a joint initiative between ESA and the EC to combine all available space- and ground-based information sources to develop an independent European environmental monitoring capacity from planetary to local scales.
Adapted from materials provided by European Space Agency.

Deep-sea Rocks Point To Early Oxygen On Earth

2009-03-26T02:06:00.001-07:00

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ScienceDaily (Mar. 25, 2009) — Red jasper cored from layers 3.46 billion years old suggests that not only did the oceans contain abundant oxygen then, but that the atmosphere was as oxygen rich as it is today, according to geologists.

This jasper or hematite-rich chert formed in ways similar to the way this rock forms around hydrothermal vents in the deep oceans today.
"Many people have assumed that the hematite in ancient rocks formed by the oxidation of siderite in the modern atmosphere," said Hiroshi Ohmoto, professor of geochemistry, Penn State. "That is why we wanted to drill deeper, below the water table and recover unweathered rocks."
The researchers drilled diagonally into the base of a hill in the Pilbara Craton in northwest Western Australia to obtain samples of jasper that could not have been exposed to the atmosphere or water. These jaspers could be dated to 3.46 billion years ago.
"Everyone agrees that this jasper is 3.46 billion years old," said Ohmoto. "If hematite were formed by the oxidation of siderite at any time, the hematite would be found on the outside of the siderite, but it is found inside," he reported in a recent issue of Nature Geoscience.
The next step was to determine if the hematite formed near the water's surface or in the depths. Iron compounds exposed to ultra violet light can form ferric hydroxide, which can sink to the bottom as tiny particles and then be converted to hematite at temperatures of at least 140 degrees Fahrenheit.
"There are a number of cases around the world where hematite is formed in this way," says Ohmoto. "So just because there is hematite, there is not necessarily oxygen in the water or the atmosphere."
The key to determining if ultra violet light or oxygen formed the hematite is the crystalline structure of the hematite itself. If the precursors of hematite were formed at the surface, the crystalline structure of the rock would have formed from small particles aggregating producing large crystals with lots of empty spaces between. Using transmission electron microscopy, the researchers did not find that crystalline structure.
"We found that the hematite from this core was made of a single crystal and therefore was not hematite made by ultra violet radiation," said Ohmoto.
This could only happen if the deep ocean contained oxygen and the iron rich fluids came into contact at high temperatures. Ohmoto and his team believe that this specific layer of hematite formed when a plume of heated water, like those found today at hydrothermal vents, converted the iron compounds into hematite using oxygen dissolved in the deep ocean water.
"This explains why this hematite is only found in areas with active submarine volcanism," said Ohmoto. "It also means that there was oxygen in the atmosphere 3.46 billion years ago, because the only mechanism for oxygen to exist in the deep oceans is for there to be oxygen in the atmosphere."
In fact, the researchers suggest that to have sufficient oxygen at depth, there had to be as much oxygen in the atmosphere 3.46 billion years ago as there is in today's atmosphere. To have this amount of oxygen, the Earth must have had oxygen producing organisms like cyanobacteria actively producing it, placing these organisms much earlier in Earth's history than previously thought.
"Usually, we look at the remnant of what we think is biological activity to understand the Earth's biology," said Ohmoto. "Our approach is unique because we look at the mineral ferric oxide to decipher biological activity."
Ohmoto suggests that this approach eliminates the problems trying to decide if carbon residues found in sediments were biologically created or simply chemical artifacts.
Other researchers on the study included Masamichi Hoashi, graduate student at Kagoshima University, Japan; Arthur H. Hickman, geologist with the Geological Survey of Western Australia; Satoshi Utsunomiya, Kyushu University, Japan, and David C. Bevacqua and Tsubasa Otake, former Penn State master's and doctoral students, Penn State; and Yumiko Watanabe, research associate, Penn State.
The NASA Astrobiology Institute supported this work.
Adapted from materials provided by Penn State.

Climate Warming Affects Antarctic Ice Sheet Stability

2009-03-23T11:48:00.001-07:00

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ScienceDaily (Mar. 22, 2009) — A five-nation scientific team has published new evidence that even a slight rise in atmospheric concentrations of carbon dioxide, one of the gases that drives global warming, affects the stability of the West Antarctic Ice Sheet (WAIS). The massive WAIS covers the continent on the Pacific side of the Transantarctic Mountains. Any substantial melting of the ice sheet would cause a rise in global sea levels.

The research, which was published in the March 19 issue of the journal Nature, is based on investigations by a 56-member team of scientists conducted on a 1,280-meter (4,100-foot)-long sedimentary rock core taken from beneath the sea floor under Antarctica's Ross Ice Shelf during the first project of the ANDRILL (ANtarctic geological DRILLing) research program--the McMurdo Ice Shelf (MIS) Project.
"The sedimentary record from the ANDRILL project provides scientists with an important analogue that can be used to help predict how ice shelves and the massive WAIS will respond to future global warming over the next few centuries," said Ross Powell, a professor of geology at Northern Illinois University.
"The sedimentary record indicates that under global warming conditions that were similar to those projected to occur over the next century, protective ice shelves could shrink or even disappear and the WAIS would become vulnerable to melting," Powell said. "If the current warm period persists, the ice sheet could diminish substantially or even disappear over time. This would result in a potentially significant rise in sea levels."
ANDRILL--which involves scientists from the United States, New Zealand, Italy and Germany--refines previous findings about the relationship between atmospheric carbon dioxide concentration, atmospheric and oceanic temperatures, sea level rise and natural cycles in Earth's orbit around the Sun, through the study of sediment and rock cores that are a geological archive of past climate.
The dynamics of ice sheets, including WAIS, are not well understood, and improving scientists' comprehension of the mechanisms that control the growth, melting and movements of ice sheets was one of NSF's research priorities during the International Polar Year (IPY). The IPY field campaign, which officially ended March 2009, has been an intense scientific campaign to explore new frontiers in polar science, improve our understanding of the critical role of the polar regions in global processes, and educate students, teachers, and the public about the polar regions and their importance to the global system. NSF was the lead agency for U.S. IPY efforts.
The cores retrieved by ANDRILL researchers have allowed them to peer back in time to the Pliocene era, roughly 2 million to 5 million years ago. During that era, the Antarctic was in a natural climate state that was warmer than today and atmospheric carbon dioxide levels were higher. Data from the cores indicate the WAIS advanced and retreated numerous times in response to forcing driven by these climate cycles.
Powell and Tim Naish, director of Victoria University of Wellington's Antarctic Research Centre, served as co-chief scientists of the 2006-2007 ANDRILL project that retrieved the data and are lead authors in one of two companion studies published in Nature.
Naish said the new information gleaned from the core shows that changes in the tilt of Earth's rotational axis has played a major role in ocean warming that has driven repeated cycles of growth and retreat of the WAIS for the period in Earth's history between 3 million and 5 million years ago.
"It also appears that when atmospheric carbon dioxide concentrations reached 400 parts per million around four million years ago, the associated global warming amplified the effect of the Earth's axial tilt on the stability of the ice sheet," he said.
"Carbon dioxide concentration in the atmosphere is again approaching 400 parts per million," Naish said. "Geological archives, such as the ANDRILL core, highlight the risk that a significant body of permanent Antarctic ice could be lost within the next century as Earth's climate continues to warm. Based on ANDRILL data combined with computer models of ice sheet behavior, collapse of the entire WAIS is likely to occur on the order of 1,000 years, but recent studies show that melting has already begun."
The second ANDRILL study in Nature--led by David Pollard of Pennsylvania State University and Rob DeConto from University of Massachusetts--reports results from a computer model of the ice sheets. The model shows that each time the WAIS collapsed, some of the margins of the East Antarctic Ice Sheet also melted, and the combined effect was a global sea level rise of 7 meters above present-day levels.
Whether the beginnings of such a collapse could start 100 years from now or within the next millennium is hard to predict and depends on future atmospheric CO2 levels, the researchers said. However, the new information from ANDRILL contributes a missing piece of the puzzle as scientists try to refine their predictions of the effects of global warming.
The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice sheet behavior it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behavior of ice sheets, the IPCC report said, is one of the major uncertainties in predicting exactly how the warming of the globe will affect human populations.
"From these combined data modeling studies, we can say that past warming events caused West Antarctic ice shelves and ice grounded below sea level to melt and disappear. The modeling suggests these collapses took one to a few thousand years," Pollard said.
Pollard and DeConto also underscored the role of ocean temperatures in melting of the ice.
"It's clear from our combined research using geological data and modeling that ocean temperatures play a key role," DeConto said. "The most substantial melting of protective ice shelves comes from beneath the ice, where it is in contact with seawater. We now need more data to determine what is happening to the underside of contemporary ice shelves."
The National Science Foundation (NSF), which manages the U.S. Antarctic Program (USAP), provided about $20 million in support of the ANDRILL program. The other ANDRILL national partners contributed an additional $10 million in science and logistics support.
The ANDRILL Science Management Office, located at the University of Nebraska-Lincoln, supports science planning and the activities of the international ANDRILL Science Committee (ASC). Antarctica New Zealand is the ANDRILL project operator and has developed the drilling system in collaboration with Alex Pyne at Victoria University of Wellington and Webster Drilling and Exploration.
The U.S. Antarctic Program and Raytheon Polar Services Corporation (RPSC) supported the science team at McMurdo Station and in the Crary Science and Engineering Laboratory, while Antarctica New Zealand supported the drilling team at Scott Base.
ANDRILL scientific studies are jointly supported by: the U.S. National Science Foundation, the New Zealand Foundation for Research, the Italian Antarctic Research Program, the German Science Foundation and the Alfred Wegener Institute.
Adapted from materials provided by National Science Foundation.

Earth Science: Lithosphere Deformed And Fractured Under Indian Ocean Much Earlier Than Previously Thought

2009-03-20T12:56:00.001-07:00

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ScienceDaily (Mar. 20, 2009) — The discovery by Indian and British scientists that the Earth’s strong outer shell – the ‘lithosphere’ – within the central Indian Ocean began to deform and fracture 15.4–13.9 million years ago, much earlier than previously thought, impacts our understanding of the birth of the Himalayas and the strengthening of the Indian-Asian monsoon.

India and Asia collided around 50 million years ago as a result of plate tectonics – the large-scale movements of the lithosphere, which continue to this day. The new study, published in the scientific journal Geology, focuses on the tectonics-related deformation of the lithosphere below the central Indian Ocean.
“Compression of the lithosphere has caused large-scale buckling and cracking,” says team member Professor Jon Bull of the University of Southampton’s School of Ocean and Earth Science based at the National Oceanography Centre; “The ocean floor has been systematically transformed into folds 100-300 kilometres long and 2,000-3,000 metres high, and there are also regularly spaced faults or fractures that are evident from seismic surveys and ocean drilling.”
The onset of this deformation marks the start of major geological uplift of the Himalayas and the Tibetan Plateau, some 4,000 km further to the north, due to stresses within the wider India-Asia area. Some studies indicate that it began around 8.0–7.5 million years ago, while others have indicated that it started before 8.0 million years ago, and perhaps much earlier.
This controversy has now been addressed by Professor Bull and his colleagues Dr Kolluru Krishna of the National Institute of Oceanography in India, and Dr Roger Scrutton of Edinburgh University. They have analysed seismic profiles of 293 faults in the accumulated sediments of the Bengal Fan. This is the world’s largest submarine fan, a delta-shaped accumulation of land-derived sediments covering the floor of the Bay of Bengal.
They demonstrate that deformation of the lithosphere within the central Indian Ocean started around 15.4–13.9 million years ago, much earlier than most previous estimates. This implies considerable Himalayan uplift before 8.0 million years ago, which is when many geologists believe that the strong seasonal winds of the India-Asia monsoon first started.
“However,” says Professor Bull, “the realisation that the onset of lithospheric deformation within the central Indian Ocean occurred much earlier fits in well with more recent evidence that the strengthening of the monsoon was linked to the early geological uplift of the Himalayas and Tibetan plateau up to 15-20 million years ago.”
Intensive deep-sea drilling within the Bengal Fan should provide better age estimates for the onset of deformation of the lithosphere in the central Indian Ocean and help settle the controversy.
The research was funded by India’s Council of Scientific and Industrial Research (CSIR), and the United Kingdom’s Royal Society and Natural Environment Research Council (NERC).
Adapted from materials provided by National Oceanography Centre, Southampton.

Ozone: New Simulation Shows Consequences Of A World Without Earth's Natural Sunscreen

2009-03-19T07:18:00.000-07:00

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ScienceDaily (Mar. 19, 2009) — The year is 2065. Nearly two-thirds of Earth's ozone is gone -- not just over the poles, but everywhere. The infamous ozone hole over Antarctica, first discovered in the 1980s, is a year-round fixture, with a twin over the North Pole. The ultraviolet (UV) radiation falling on mid-latitude cities like Washington, D.C., is strong enough to cause sunburn in just five minutes. DNA-mutating UV radiation is up 650 percent, with likely harmful effects on plants, animals and human skin cancer rates.

Such is the world we would have inherited if 193 nations had not agreed to ban ozone-depleting substances, according to atmospheric chemists at NASA's Goddard Space Flight Center, Greenbelt, Md., Johns Hopkins University, Baltimore, and the Netherlands Environmental Assessment Agency, Bilthoven.
Led by Goddard scientist Paul Newman, the team simulated "what might have been" if chlorofluorocarbons (CFCs) and similar chemicals were not banned through the treaty known as the Montreal Protocol. The simulation used a comprehensive model that included atmospheric chemical effects, wind changes, and radiation changes. The analysis has been published online in the journal Atmospheric Chemistry and Physics.
"Ozone science and monitoring has improved over the past two decades, and we have moved to a phase where we need to be accountable," said Newman, who is co-chair of the United Nations Environment Programme's Scientific Assessment Panel to review the state of the ozone layer and the environmental impact of ozone regulation. "We are at the point where we have to ask: Were we right about ozone? Did the Montreal Protocol work? What kind of world was avoided by phasing out ozone-depleting substances?"
Ozone is Earth's natural sunscreen, absorbing and blocking most of the incoming UV radiation from the sun and protecting life from DNA-damaging radiation. The gas is naturally created and replenished by a photochemical reaction in the upper atmosphere where UV rays break oxygen molecules (O2) into individual atoms that then recombine into three-part molecules (O3). As it is moved around the globe by upper level winds, ozone is slowly depleted by naturally occurring atmospheric gases. It is a system in natural balance.
But chlorofluorocarbons -- invented in 1928 as refrigerants and as inert carriers for chemical sprays -- upset that balance. Researchers discovered in the 1970s and 1980s that while CFCs are inert at Earth's surface, they are quite reactive in the stratosphere (10 to 50 kilometers altitude, or 6 to 31 miles), where roughly 90 percent of the planet's ozone accumulates. UV radiation causes CFCs and similar bromine compounds in the stratosphere to break up into elemental chlorine and bromine that readily destroy ozone molecules. Worst of all, such ozone depleting substances can reside for several decades in the stratosphere before breaking down.
In the 1980s, ozone-depleting substances opened a wintertime "hole" over Antarctica and opened the eyes of the world to the effects of human activity on the atmosphere. By 1987, the World Meteorological Organization and United Nations Environment Program had brought together scientists, diplomats, environmental advocates, governments, industry representatives, and non-governmental organizations to forge an agreement to phase out the chemicals. In January 1989, the Montreal Protocol went into force, the first-ever international agreement on regulation of chemical pollutants.
“The regulation of ozone depleting substances was based upon the evidence gathered by the science community and the consent of industry and government leaders," Newman noted. "The regulation pre-supposed that a lack of action would lead to severe ozone depletion, with consequent severe increases of solar UV radiation levels at the Earth’s surface."
In the new analysis, Newman and colleagues "set out to predict ozone losses as if nothing had been done to stop them." Their "world avoided" simulation took months of computer time to process.
The team started with the Goddard Earth Observing System Chemistry-Climate Model (GEOS-CCM), an earth system model of atmospheric circulation that accounts for variations in solar energy, atmospheric chemical reactions, temperature variations and winds, and other elements of global climate change. For instance, the new model accounts for how changes in the stratosphere influence changes in the troposphere (the air masses near Earth's surface). Ozone losses change the temperature in different parts of the atmosphere, and those changes promote or suppress chemical reactions.
The researchers then increased the emission of CFCs and similar compounds by 3 percent per year, a rate about half the growth rate for the early 1970s. Then they let the simulated world evolve from 1975 to 2065.
By the simulated year 2020, 17 percent of all ozone is depleted globally, as assessed by a drop in Dobson Units (DU), the unit of measurement used to quantify a given concentration of ozone. An ozone hole starts to form each year over the Arctic, which was once a place of prodigious ozone levels.
By 2040, global ozone concentrations fall below 220 DU, the same levels that currently comprise the "hole" over Antarctica. (In 1974, globally averaged ozone was 315 DU.) The UV index in mid-latitude cities reaches 15 around noon on a clear summer day (a UV index of 10 is considered extreme today.), giving a perceptible sunburn in about 10 minutes. Over Antarctica, the ozone hole becomes a year-round fixture.
In the 2050s, something strange happens in the modeled world: Ozone levels in the stratosphere over the tropics collapse to near zero in a process similar to the one that creates the Antarctic ozone hole.
By the end of the model run in 2065, global ozone drops to 110 DU, a 67 percent drop from the 1970s. Year-round polar values hover between 50 and 100 DU (down from 300-500 in 1960). The intensity of UV radiation at Earth's surface doubles; at certain shorter wavelengths, intensity rises by as much as 10,000 times. Skin cancer-causing radiation soars.
"Our world avoided calculation goes a little beyond what I thought would happen," said Goddard scientist and study co-author Richard Stolarski, who was among the pioneers of atmospheric ozone chemistry in the 1970s. "The quantities may not be absolutely correct, but the basic results clearly indicate what could have happened to the atmosphere. And models sometimes show you something you weren't expecting, like the precipitous drop in the tropics."
"We simulated a world avoided," said Newman, "and it's a world we should be glad we avoided."
The real world of CFC regulation has been somewhat kinder. Production of ozone-depleting substances was mostly halted about 15 years ago, though their abundance is only beginning to decline because the chemicals can reside in the atmosphere for 50 to 100 years. The peak abundance of CFCs in the atmosphere occurred around 2000, and has decreased by roughly 4 percent to date.
Stratospheric ozone has been depleted by 5 to 6 percent at middle latitudes, but has somewhat rebounded in recent years. The largest recorded Antarctic ozone hole was recorded in 2006.
"I didn't think that the Montreal Protocol would work as well as it has, but I was pretty naive about the politics," Stolarski added. "The Montreal Protocol is a remarkable international agreement that should be studied by those involved with global warming and the attempts to reach international agreement on that topic."
Adapted from materials provided by NASA/Goddard Space Flight Center.

Drought, Urbanization Were Ingredients For Atlanta's Perfect Storm

2009-03-19T00:16:00.001-07:00

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ScienceDaily (Mar. 18, 2009) — On March 14, 2008, a tornado swept through downtown Atlanta, its 130 mile-per-hour winds ripping holes in the roof of the Georgia Dome, blowing out office windows, and trashing parts of Centennial Olympic Park. It was an event so rare in an urban landscape that researchers immediately began to examine NASA satellite data and historical archives to see what weather and climatological ingredients may have combined to brew such a storm.

Though hundreds of tornadoes form each year across the United States, records of "downtown tornadic events" are quite rare. The 2008 Atlanta tornado—the first in the city's recorded history—was also unique because it developed during extreme drought conditions.
In a NASA-funded study, researchers from Purdue University in West Lafayette, Ind., and the University of Georgia (UGA) in Athens found that intermittent rain in the days before the storms—though providing temporary drought relief—may have moistened some areas enough to create favorable conditions for severe storms to form and intensify. Additionally, the sprawling urban landscape may have given the storms the extra, turbulent energy needed to spin up a tornado. The researchers reported their findings in January at the annual meeting of the American Meteorological Society.
"The Atlanta tornado, though forecasted well, caught us by surprise because it evolved rapidly under very peculiar conditions during a drought and over a downtown area," said Dev Niyogi, an assistant professor of regional climatology at Purdue and lead author of the modeling study. "We wanted to know why it hit Atlanta during one of the longest, harshest droughts the southeast has experienced. Was it a manifestation of the drought? Does urban development have an effect on such a storm?"
Such questions are becoming more relevant as the Intergovernmental Panel on Climate Change, NASA, and other institutions investigate the relationships between extreme water cycle events (such as drought), land cover change, weather, and climate change.
In the southeastern U.S., tornadoes are quite common in the spring when upper level wind patterns, surface moisture, and surface weather features promote severe weather. But moisture was scarce in the weeks leading up to the March 2008 Atlanta tornado, and likely should have suppressed a storm, according to atmospheric scientist Marshall Shepherd of UGA. Shepherd, Niyogi and colleagues recently completed a 50-year climatological assessment that finds tornadic activity is often suppressed during droughts in the Southeast.
To get to the bottom of how such a storm could have developed despite the drought, Purdue researchers Niyogi, Ming Lei, and Anil Kumar—along with Shepherd—investigated reports of isolated rain showers that had swept through parts of Alabama and northwest Georgia in the 48 hours prior to the tornado. They suspected that these "wet pockets" might have triggered—but more likely enhanced—the initial thunderstorms.
The scattered rainfall fell between areas that received no rain, setting up pockets of high humidity between areas of warm, dry air. The wet and dry areas may have acted as weak atmospheric fronts or may have promoted air circulation and evaporation that could have intensified the storms. A similar phenomenon promotes severe thunderstorms in Florida, where moist sea breezes interact with dry interior air masses.
Niyogi and Shepherd also found evidence that storm intensity was amplified by the heat-retaining effects of Atlanta's buildings and streets. The "heat island" effect leads to warmer air temperatures in urban areas because impervious surfaces like glass, metal, concrete and asphalt absorb, reflect, and store heat differently than tree or grass-covered land. Urban environments heat the air and cause moisture to rise quickly, creating a "thunderstorm pump" that can fuel or intensify storms. In March 2008, the differences in soil moisture and Atlanta's sprawling land cover may have provided the perfect blend for storms to intensify.
"A thunderstorm, energized by moist pockets within a drought region, grew into a tornado-causing severe thunderstorm because of weather instabilities it encountered at the rural-urban boundary," Niyogi explained.
"Drought and urbanization do not cause the thunderstorms or tornado, but ultimately they added fuel to the fire of an already energized storm," he added. "The variable rain bands created patches of land that were wet and dry, green and not green. The combination created surface boundaries that can destabilize the weather system and energize an approaching storm, providing the one-two punch."
Niyogi, Shepherd, and colleagues used the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA's Aqua satellite to assess the state of ground vegetation immediately before and after the storm, as well the long-term differences before and during the drought. The researchers also examined rainfall estimates captured by NASA's Tropical Rainfall Measurement Mission satellite to identify the unusual bands of rainfall two days before the tornado.
Finally, they examined soil moisture data from the Japanese Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) instrument on NASA's Aqua satellite to evaluate the intensity of the drought at the time of the tornado. When these real drought and urban land cover conditions were included in the team's atmosphere-land surface computer models, the simulations produced a more intense storm that mirrored reality.
"Our findings highlight the difficulty in detangling the influences of the atmosphere and of Earth's surface within the weather-hydroclimate system," said Shepherd. "Soil moisture and urban land cover are not well-represented in weather models, but a new look at satellite data offers a fresh opportunity to improve forecasts."
"With many studies suggesting more potential for urbanization and droughts in our future," Niyogi added, "it will be important to see if this kind of intense storm development could happen more frequently in future climates."
Adapted from materials provided by NASA/Goddard Space Flight Center.

Lessons From Hurricane Rita Not Practiced During Hurricane Ike

2009-03-18T13:51:00.001-07:00

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ScienceDaily (Mar. 19, 2009) — A new Rice University report released yesterday, exactly six months after Hurricane Ike slammed the Texas Gulf Coast, suggests that people did not practice the lessons learned from Hurricane Rita.

According to the study, 75 percent of Harris County residents say they would evacuate if a Category 4 hurricane threatened Houston. This is a significant potential increase over the 24 percent of residents who left during the Category 2 Hurricane Ike. It's also a significant increase over the 52 percent of Harris County residents who evacuated in 2005 during the Category 4 Hurricane Rita but found themselves stuck in miles-long traffic jams on highways or stranded as the storm approached.
"Essentially, this study shows that people didn't learn from Hurricane Rita," said the report's co-author Robert Stein, the Lena Gohlman Fox Professor of Political Science at Rice. "Had Hurricane Ike been a severe storm -- a Category 3 or 4 -- more people would have evacuated, and we would have experienced roadway gridlock."
The reports shows that significantly fewer people evacuated during Hurricane Ike than during Hurricane Rita, but a large portion of the population left areas that were not under an evacuation order.
"The timing of evacuations showed no improvement over the experience during Hurricane Rita, when roadways experienced paralyzing gridlock," Stein said. "People evacuating from hurricane Ike all left too late, potentially creating the same conditions that existed during Hurricane Rita had a larger population evacuated."
The report details the results of surveys that assessed people's experience before, during and after each hurricane's landfall. The surveys were conducted in the weeks immediately after each storm -- Sept. 29-Oct. 3 for the Hurricane Rita survey, and Sept. 23-Oct. 24 for the Hurricane Ike survey.
The report is intended to enable policymakers and leaders to be more effective in getting their constituents to comply with evacuation orders.
The report also found:
Local television weather reporters were the most-relied-upon source of information for both hurricanes. During Hurricane Ike, the Weather Channel was the second most-relied-upon source.
In non-evacuation zones during Hurricane Rita, 40 percent of residents evacuated. These "shadow evacuees" were largely responsible for the road congestion. During Hurricane Ike, that number fell to 21 percent.
Evacuees during Hurricane Ike responded correctly by taking fewer vehicles and slightly more people per vehicle. This was particularly true for people from areas under an evacuation order.
The release of this report coincides with a free public forum at Rice University March 12 featuring Houston Mayor Bill White and Harris County Judge Ed Emmett discussing the leadership challenges they had to overcome to guide Houston through the disaster. "Leadership in Crisis: Guiding Houston through the Storm" will be held from 6 to 7 p.m. in Sewall Hall, Room 301, on the Rice campus, 6100 Main St. Stein and report co-authors Leonardo Dueñas-Osorio, assistant professor in civil and environmental engineering, and Devika Subramanian, professor of computer science and in electrical and computer engineering, will be available to take questions before and after the event.
The full report is available at http://www.media.rice.edu/images/media/0312_CCE_HurricaneIke_report.pdf

Earth's Crust Melts Easier Than Previously Thought

2009-03-18T13:48:00.000-07:00

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ScienceDaily (Mar. 19, 2009) — A University of Missouri study just published in Nature has found that the Earth's crust melts easier than previously thought. In the study, researchers measured how well rocks conduct heat at different temperatures and found that as rocks get hotter in the Earth's crust, they become better insulators and poorer conductors.

This finding provides insight into how magmas are formed and will lead to better models of continental collision and the formation of mountain belts.
"In the presence of external heat sources, rocks will heat up more efficiently than previously thought," said Alan Whittington, professor of geological sciences in the MU College of Arts and Science. "We applied our findings to computer models that predict what happens to rocks when they get buried and heat up in mountain belts, such as the Himalayas today or the Black Hills in South Dakota in the geologic past. We found that strain heating, caused by tectonic movements during mountain belt formation, quite easily triggers crustal melting."
In the study, researchers used a laser-based technique to determine how long it took heat to conduct through different rock samples. In all of the samples, thermal diffusivity, or how well a material conducts heat, decreased rapidly with increasing temperatures. Researchers found the thermal diffusivity of hot rocks and magmas to be half that of what had been previously assumed.
"Most crustal melting on the Earth comes from intrusions of hot basaltic magma from the Earth's mantle," said Peter Nabelek, professor of geological sciences in the MU College of Arts and Science. "The problem is that during continental collisions, we don't see intrusions of basaltic magma into continental crust. These experiments suggest that because of low thermal diffusivity, strain heating is much faster and more efficient, and once rocks get heated, they stay hotter for much longer. Of course, these processes take millions of years to occur and we can only simulate them on a computer. This new data will allow us to create computer models that more accurately represent processes that occur during continental collisions."
The study was co-authored by Whittington, Nabelek and Anne Hofmeister, a professor at Washington University. The National Science Foundation funded this research.
Journal reference:
. Temperature-dependent thermal diffusivity of the Earth's crust and implications for magmatism. Nature, March 19, 2009
Adapted from materials provided by University of Missouri-Columbia, via EurekAlert!, a service of AAAS.

Tree-eating Bugs Seen By Satellite As They Denude Invasive Tamarisk Trees In Southwest U.S.

2009-03-18T03:34:00.001-07:00

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ScienceDaily (Mar. 18, 2009) — More than 150 years after a small Eurasian tree named tamarisk or saltcedar started taking over river banks throughout the U.S. Southwest, saltcedar leaf beetles were unleashed to defoliate the exotic invader.

Now, University of Utah scientists say their new study shows it is feasible to use satellite data to monitor the extent of the beetle's attack on tamarisk, and whether use of the beetles may backfire with unintended environmental consequences.
"We don't have any idea of the long-term impacts of using the beetles; their release may have unexpected repercussions," says Philip Dennison, an assistant professor of geography and first author of the study scheduled for online publication later this month in the journal Remote Sensing of Environment.
"The impact of this defoliation is largely unknown," says study co-author Kevin Hultine, a research assistant professor of biology at the University of Utah. "The net impact of controlling tamarisk could be positive or negative."
"We would like on-the-ground scientists and managers to understand and think about the long-term impact – what are these riparian [riverbank] areas going to look like 15 years from now, and how can we can maintain ecosystems" as well as water flows for farms, cities and river recreation, Hultine says.
Dennison and Hultine conducted the study with Jim Ehleringer, a distinguished professor of biology at the University of Utah; physical scientist Pamela Nagler, of the U.S. Geological Survey in Tucson, Ariz.; and Edward Glenn, a University of Arizona environmental scientist.
A Shady Invader from Eurasia
Anyone who has rafted Southwestern rivers like the Green and Colorado knows about the shady thickets of tamarisk that line the riverbanks. The trees can grow up to 30 feet tall. There are about 10 species of tamarisk.
The U.S. Animal and Plant Health Inspection Service (APHIS) says saltcedar or tamarisk is "a highly invasive, exotic weed" in the form of "a large shrub or small tree that was introduced to North America from Asia in the early 1800s. The plant has been used for windbreaks, ornamentals, and erosion control. By 1850, saltcedar had infested river systems and drainages in the Southwest, often displacing native vegetation."
"By 1938, infestations were found from Florida to California and as far north as Idaho," according to APHIS. "Saltcedar continues to spread rapidly and currently infests water drainages and areas throughout the United States."
Tamarisk dominates riverbank habitats, limiting camping areas for river runners, reducing diversity and providing poor habitat for some species of wildlife. Tamarisk also raises the risk of fires that destroy cottonwoods and other native plants but not tamarisk, which re-sprouts from roots. And tamarisk forms a dense canopy, also helping wipe out competing plants. Finally, tamarisk has a bad rap as a water-sucking wastrel that dries springs, lowers water tables and reduces stream flows, even impairing boating.
Dennison and Hultine say recent research indicates tamarisk's thirst is overstated.
"Some of the earliest research on tamarisk water use suggested tamarisk uses dramatically more water than other tree species," Hultine says. "So a lot of estimates on water loss over entire river reaches are based on information that now has been discredited in the scientific literature."
Hultine believes that unless aggressive programs to restore defoliated areas are implemented, tamarisk will be replaced by other invaders – Russian knapweed, Russian olive and pepperweed – that may use more water than tamarisk. Eradicating tamarisk with beetles also may reduce bird habitat, he adds.
Monitoring the Attack of the Tamarisk-Munching Beetles
The saltcedar leaf beetle, Diorhabda elongata, was brought to the U.S. from Kazakhstan. After an environmental assessment, APHIS approved them for tamarisk control.
Dennison says thousands of the beetles first were released in Utah during summer 2004, then again in summer 2005 and 2006 at locations along the Colorado River near Moab. Widespread defoliation of tamarisk in the area was noted during summer 2007.
Because long stretches of rivers in the Colorado River Basin are remote, Dennison and colleagues decided to test the feasibility of using satellite images to detect tamarisk leaf loss due to the spread of the saltcedar leaf beetles.
They mapped 56 accessible areas already defoliated by tamarisk, and studied if the defoliation could be detected using two instruments on Terra, one of the National Aeronautics and Space Administration's Earth-observing satellites.
Both instruments make images using red and near-infrared light. Plant pigments absorb red from sunlight and reflect near-infrared. In near-infrared images, tamarisk-covered areas appear red. Defoliated areas appear brown or black because there are no leaves to absorb red light and reflect near-infrared light. The two instruments are:
ASTER, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, obtains relatively high-resolution images, with each pixel covering an area about 50 feet long by 50 feet wide. It can detect big changes like tamarisk defoliation on an even smaller scale. It only obtains one to three images of a given area every summer.
MODIS, the Moderate Resolution Imaging Spectroradiometer, which can detect less detail – a pixel measures about 820 feet by 820 feet. But it can see where large swaths of tamarisk have been defoliated, Dennison says. MODIS makes daily images.
Dennison says the infrequent, higher-resolution ASTER images allow researchers to map defoliated areas, while the frequent, lower-resolution MODIS images help them detect changes in vegetation over time.
The area studied included four sites along the Colorado River northeast of Moab, and a fifth site along the tributary Dolores River at the Entrada Field Station operated by the University of Utah for education and research. The five sites covered 589 acres, and within them, researchers mapped 56 polygon-shaped areas totaling 57 acres where tamarisk had been defoliated by the beetles.
ASTER measured what is known as NVDI – the normalized difference vegetation index, which is the difference between red light absorbed by plants and near-infrared light reflected by them. The index is high when plants are present, low when they are absent.
Those satellite measurements showed minor changes in vegetation at the test sites from 2005 to 2006, but a large change between 2006 and 2007 – indicating extensive defoliation of tamarisk, even though the defoliated plants regrow within about six weeks.
The satellite's MODIS instrument used another vegetation index that also revealed widespread tamarisk defoliation at the five sites in July 2007.
While some tamarisk has died in Nevada where the beetles first were established, "we don't understand whether repeated defoliation eventually will kill most of the trees, or will they reach some point where they'll just have less leaf area over the entire year," Hultine says.
The researchers also used the satellite to estimate "evapotranspiration" – the evaporation of water from soil and the transpiration or use of water by plants – to learn more about how defoliation of tamarisk affects water use. For comparison, Hultine measured sap flow through trees, which reflects how much water is used by the trees.
Satellite estimates of tamarisk water use declined modestly as the plants were defoliated, Dennison says. The findings also were consistent with earlier research indicating tamarisk is less of a water hog than previously thought.
Dennison says he and his colleagues did the study to test the feasibility of using satellites to monitor tamarisk defoliation on an ongoing basis. That, he says, could be done by federal agencies such as the Bureau of Land Management, Bureau of Reclamation and U.S. Geological Survey.
Adapted from materials provided by University of Utah.

Robot Sub Searches For Signs Of Melting 60 Km Into An Antarctic Ice Shelf Cavity

2009-03-17T10:13:00.000-07:00

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ScienceDaily (Mar. 17, 2009) — Autosub, a robot submarine built and developed by the UK's National Oceanography Centre, Southampton, has successfully completed a high-risk campaign of six missions travelling under an Antarctic glacier.

Autosub has been exploring Pine Island Glacier, a floating extension of the West Antarctic ice sheet, using sonar scanners to map the seabed and the underside of the ice as it juts into the sea. Scientists hope to learn why the glacier has been thinning and accelerating over recent decades. Pine Island Glacier is in the Amundsen Sea, part of the South Pacific bordering West Antarctica. Changes in its flow have been observed since the early 1970s, and together with neighbouring glaciers it is currently contributing about 0.25 mm a year to global sea level rise.
Steve McPhail led the Autosub team during the ten-day survey. He said: "Autosub is a completely autonomous robot: there are no connecting wires with the ship and no pilot. Autosub has to avoid collisions with the jagged ice overhead and the unknown seabed below, and return to a pre–defined rendezvous point, where we crane it back onboard the ship.
"Adding to the problems are the sub zero water temperatures and the crushing pressures at 1000 m depth. All systems on the vehicle must work perfectly while under the ice or it would be lost. There is no hope of rescue 60 km in, with 500 metres of ice overhead."
An international team of scientists led by Dr Adrian Jenkins of British Antarctic Survey and Stan Jacobs of the Lamont-Doherty Earth Observatory, Columbia University, New York on the American ship, the RVIB Nathaniel B Palmer, has been using the robot sub to investigate the underside of the ice and measure changes in salinity and temperature of the surrounding water.
After a test mission in unusually ice-free seas in front of the face of the glacier, they started with three 60km forays under the floating glacier and extended the length of missions to 110km round-trip. In all, a distance over 500km beneath the ice was studied.
Using its sonar, the Autosub picks its way through the water, while creating a three-dimensional map that the scientists will use to determine where and how the warmth of the ocean waters drives melting of the glacier base.
"There is still much work to be done on the processing of the data", said Adrian Jenkins, "but the picture we should get of the ocean beneath the glacier will be unprecedented in its extent and detail. It should help us answer critical questions about the role played by the ocean in driving the ongoing thinning of the glacier."
The lead US researcher on the project, Stan Jacobs, is studying the Pine Island Glacier with International Polar Year (IPY) funding from the National Science Foundation (NSF). One of the IPY research goals is to better understand the dynamics of the world's massive ice sheets, including the massive West Antarctic Ice Sheet. If this were to melt completely global sea levels would rise significantly. The most recent report of the Intergovernmental Panel on Climate Change (IPCC) noted that because so little is understood about ice-sheet behaviour it is difficult to predict how ice sheets will contribute to sea level rise in a warming world. The behaviour of ice sheets the IPCC report said is one of the major uncertainties in predicting exactly how the warming of the global will affect human populations.
Complementing the Autosub exploration, other work during the 53-day NB Palmer cruise included setting out 15 moored instrument arrays to record the variability in ocean properties and circulation over the next two years, extensive profiling of 'warm' and melt-laden seawater, sampling the perennial sea ice and swath-mapping deep, glacially-scoured troughs on the sea floor.
Autosub is an AUV – Automated Underwater Vehicle, designed, developed and built at the National Oceanography Centre, Southampton with funding from the Natural Environment Research Council. Autosub has a maximum range of 400km and is powered by 5,000 ordinary D-cell batteries. The batteries are packed in bundles in pressure-tested housings. Either end of the seven-metre sub there are free-flooding areas where the payload of instruments are installed. It carries a multibeam sonar system that builds up a 3D map of the ice above and the seabed below.. It also carries precision instruments for measuring the salinity, temperature, and oxygen concentrations in the sea water within the ice cavity, which are vital to understanding the flow of water within the ice cavity and the rate of melting. Autosub is 7m long and weighs 3.5 tonnes. Travelling at 6km hour it is capable of diving up to 1600 m deep, and can operate for 72 hours (400 km) between battery changes.
Adapted from materials provided by National Oceanography Centre, Southampton (UK).

Cleaning Up Oil Spills Can Kill More Fish Than Spills Themselves

2009-03-17T10:06:00.001-07:00

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ScienceDaily (Mar. 17, 2009) — A new Queen's University study shows that detergents used to clean up spills of diesel oil actually increase its toxicity to fish, making it more harmful.

"The detergents may be the best way to treat spills in the long term because the dispersed oil is diluted and degraded," says Biology professor Peter Hodson. "But in the short term, they increase the bioavailability and toxicity of the fuel to rainbow trout by 100-fold."
The detergents are oil dispersants that decrease the surface tension between oil and water, allowing floating oil to mix with water as tiny droplets. Dr. Hodson and his team found that dispersion reduces the potential impacts of oil on surface-dwelling animals, While this should enhance biodegradation, it also creates a larger reservoir of oil in the water column.
This increases the transfer of hydrocarbons from oil to water, Dr. Hodson explains. The hydrocarbons pass easily from water into tissues and are deadly to fish in the early stages of life. "This could seriously impair the health of fish populations, resulting in long-term reductions in economic returns to fisheries," he says.
The study is published in the journal, Environmental Toxicology and Chemistry.
The researchers also determined that even though chemical dispersants are not typically used in freshwater, turbulent rivers can disperse spilled diesel and create similar negative effects.
"It doesn't matter if the oil is being dispersed by chemicals or by the current," says Dr. Hodson. "Now that we know how deadly dispersed oil is, it is important to assess the risks of diesel spills to fish and fisheries in terms of the spill location, and the timing relative to fish spawning and development."
Funding for the study was provided by the Natural Sciences and Engineering Research Council of Canada (NSERC) and by Petroleum Research Atlantic Canada. Also on the research team are Allison Schein and Jason Scott from Queen's School of Environmental Studies and environmental consultant Lizzy Mos.
Adapted from materials provided by Queen's University.

Climate-related Changes Affect Life On The Antarctic Peninsula

2009-03-17T02:58:00.001-07:00

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ScienceDaily (Mar. 17, 2009) — Scientists have long established that the Antarctic Peninsula is one of the most rapidly warming spots on Earth. Now, new research using detailed satellite data indicates that the changing climate is affecting not just the penguins at the apex of the food chain, but simultaneously the microscopic life that is the base of the ecosystem.

The research was published in the journal Science by researchers with the National Science Foundation's (NSF) LTER (Long Term Ecological Research) program. The LTER, which has 26 sites around the globe, including two in Antarctica, enables tracking of ecological variables over time, so that the mechanisms of climate change impact on ecosystems can be revealed. The specific findings were made by researchers with the Palmer LTER, using data collected near Palmer Station and from the research vessel Laurence M. Gould. Both Palmer Station and the Laurence M. Gould are operated by NSF's Office of Polar Programs.
Hugh Ducklow, of the Marie Biological Laboratory at Woods Hole, the principal investigator for the Palmer LTER project, said that the new findings are scientifically significant, but they also are consistent with the climate trends on the Peninsula and other observed changes.
However, it took new scientific tools and analytical work by post-doctoral fellow Martin Montes Hugo to verify scientifically what scientists had been inferring from other changes for some time.
"I have to say the findings weren't a surprise; I think with the weight of all the other observations that we had on changes happening to organisms higher up in the food chain, we thought that phytoplankton weren't going to escape this level of climate change," Ducklow said. "But it took Martin to have all the right tools and the abilities to go in and do the analysis and prove what we suspected."
Those data, gathered over years, were essential to tracking patterns that supported the new findings.
"That's the beauty of the LTER program," he added.
Over the past 50 years, winter temperatures on the Peninsula have risen five times faster than the global average and the duration of sea-ice coverage has decreased. A warm, moist maritime climate has moved into the northern Peninsula region, pushing the continental, polar conditions southward.
As a result, the prevalence of species that depend on sea ice, such as Adelie penguins, Antarctic silverfish and krill, has decreased in the Peninsula's northern region, and new species that typically avoid ice, such as Gentoo and Chinstrap penguins, and lanternfish are moving into the habitat.
The LTER researchers show that satellite data on ocean color, temperature, sea ice and winds, indicate that phytoplankton at the base of the food chain are also responding to changes in sea-ice cover and winds driven by climate change. However, there are contrasting changes in northern and southern regions, and the satellite and ground-based data provide insights into the forcing mechanisms for each region.
The researchers weren't surprised that primary productivity in the waters of the Peninsula has changed dramatically over the last 20 years. But the contrasting changes in the north and south were a surprise.
In the north, where ice-dependent species are disappearing, sea ice cover has declined and wind stress has increased. The wind intensity and reduced sea ice causes greater mixing of the surface ocean waters. The result--a deepening of the surface mixed layer that lowers primary productivity rates and causes changes in phytoplankton species, because phytoplankton cells are exposed to less light.
Conversely, in the southern Peninsula waters, where ice-dependent species continue to thrive, the situation is reversed. There, sea ice loss has been in areas where it formerly covered most of the ocean surface for most of the year. Now, ice is less prevalent, exposing more water to sunlight and stimulating phytoplankton growth. The ice loss in the South, combined with less wind stress, promotes the formation of a shallower mixed layer, with increased light and the development of large phytoplankton cells, such as diatoms. Diatoms, single-celled creatures, form the base of the rich Antarctic food web that includes krill, penguins and whales.
Journal reference:
Montes-Hugo et al. Recent Changes in Phytoplankton Communities Associated with Rapid Regional Climate Change Along the Western Antarctic Peninsula. Science, March 13, 2009; 323 (5920): 1470 DOI: 10.1126/science.1164533
Adapted from materials provided by National Science Foundation.

New Tool For Study Of Air Quality Developed

2009-03-16T23:59:00.000-07:00

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ScienceDaily (Mar. 17, 2009) — Air quality models have achieved a great degree of sophistication over the last few years thanks mainly to scientific and computational advances. These are tools that simulate the dynamics of the atmosphere and estimate the impact of particular sources of contamination such as industries or traffic on air quality so that plans and decisions can then be made according to the produced results.

The Grupo de Modelos y Software para el medio Ambiente of the Facultad de Informática at the Universidad Politécnica de Madrid has developed a very sophisticated tool (OPANA) that estimates the impact of air quality on the health of citizens using last generation models.
This tool is based on very advanced numerical methods that produce extremely precise measurements of the concentration of a certain atmospheric contaminant that a person breathes in a determined time and place, from a particular source (an industry, an incinerator, a motorway, etc.). It is possible to determine the consequent impact under almost any circumstances or distance from the source thanks to the enormous calculating power available today.
In order to ensure that the obtained results are reliable, it is necessary to introduce accurate data into the tool. The tool requires detailed information about the topography of the site under study, the different uses of land obtained through remote sensing, meteorological information, relevant information about the surroundings of the area under study, and above all an accurate estimate of the emissions that occur in the area and its surroundings.
With these tools, it is possible to evaluate the impact that a new industry would have on the atmospheric contamination of an area and carry out experiments using different scenarios to be compared against the current conditions. In this way, the best decisions can be made to protect the health of inhabitants of the area.
Journal reference:
Sanjose et al. The evaluation of the air quality impact of an incinerator by using MM5-CMAQ-EMIMO modeling system: North of Spain case study. Environment International, 2008; 34 (5): 714 DOI: 10.1016/j.envint.2007.12.010
Adapted from materials provided by Universidad Politécnica de Madrid, via AlphaGalileo.

Atmospheric 'Sunshade' Could Reduce Solar Power Generation

2009-03-16T09:15:00.000-07:00

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ScienceDaily (Mar. 16, 2009) — The concept of delaying global warming by adding particles into the upper atmosphere to cool the climate could unintentionally reduce peak electricity generated by large solar power plants by as much as one-fifth, according to a new NOAA study.

“Injecting particles into the stratosphere could have unintended consequences for one alternative energy source expected to play a role in the transition away from fossil fuels,” said author Daniel Murphy, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colo.
The Earth is heating up as fossil-fuel burning produces carbon dioxide, the primary heat-trapping gas responsible for man-made climate change. To counteract the effect, some geoengineering proposals are designed to slow global warming by shading the Earth from sunlight.
Among the ideas being explored is injecting small particles into the upper atmosphere to produce a climate cooling similar to that of large volcanic eruptions, such as Mt. Pinatubo’s in 1991. Airborne sulfur hovering in the stratosphere cooled the Earth for about two years following that eruption.
Murphy found that particles in the stratosphere reduce the amount and change the nature of the sunlight that strikes the Earth. Though a fraction of the incoming sunlight bounces back to space (the cooling effect), a much larger amount becomes diffuse, or scattered, light.
On average, for every watt of sunlight the particles reflect away from the Earth, another three watts of direct sunlight are converted to diffuse sunlight. Large power-generating solar plants that concentrate sunlight for maximum efficiency depend solely on direct sunlight and cannot use diffuse light.
Murphy verified his calculations using long-term NOAA observations of direct and diffuse sunlight before and after the 1991 eruption.
After the eruption of Mt. Pinatubo, peak power output of Solar Electric Generating Stations in California, the largest collective of solar power plants in the world, fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.
“The sensitivity of concentrating solar systems to stratospheric particles may seem surprising,” said Murphy. “But because these systems use only direct sunlight, increasing stratospheric particles has a disproportionately large effect on them.”
Nine Solar Electric Generating Stations operate in California and more are running or are under construction elsewhere in the world. In sunny locations such systems, which use curved mirrors or other concentrating devices, generate electricity at a lower cost than conventional photovoltaic, or solar, cells.
Flat photovoltaic and hot water panels, commonly seen on household roofs, use both diffuse and direct sunlight. Their energy output would decline much less than that from concentrating systems.
Even low-tech measures to balance a home’s energy, such as south-facing windows for winter heat and overhangs for summer shade, would be less effective if direct sunlight is reduced.
The findings recently appeared in the journal Environmental Science and Technology.
Journal reference:
Daniel M. Murphy. Effect of Stratospheric Aerosols on Direct Sunlight and Implications for Concentrating Solar Power. Environmental Science & Technology, 2009; 090311080700076 DOI: 10.1021/es802206b
Adapted from materials provided by National Oceanic And Atmospheric Administration.

Sea Level Rise Due To Global Warming Poses Threat To New York City

2009-03-16T03:53:00.001-07:00

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ScienceDaily (Mar. 16, 2009) — Global warming is expected to cause the sea level along the northeastern U.S. coast to rise almost twice as fast as global sea levels during this century, putting New York City at greater risk for damage from hurricanes and winter storm surge, according to a new study led by a Florida State University researcher.

Jianjun Yin, a climate modeler at the Center for Ocean-Atmospheric Prediction Studies (COAPS) at Florida State, said there is a better than 90 percent chance that the sea level rise along this heavily populated coast will exceed the mean global sea level rise by the year 2100. The rising waters in this region -- perhaps by as much as 18 inches or more -- can be attributed to thermal expansion and the slowing of the North Atlantic Ocean circulation because of warmer ocean surface temperatures.
Yin and colleagues Michael Schlesinger of the University of Illinois at Urbana-Champaign and Ronald Stouffer of Geophysical Fluid Dynamics Laboratory at Princeton University are the first to reach that conclusion after analyzing data from 10 state-of-the-art climate models, which have been used for the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report. Yin's study is published in the journal Nature Geoscience.
"The northeast coast of the United States is among the most vulnerable regions to future changes in sea level and ocean circulation, especially when considering its population density and the potential socioeconomic consequences of such changes," Yin said. "The most populous states and cities of the United States and centers of economy, politics, culture and education are located along that coast."
The researchers found that the rapid sea-level rise occurred in all climate models whether they depicted low, medium or high rates of greenhouse-gas emissions. In a medium greenhouse-gas emission scenario, the New York City coastal area would see an additional rise of about 8.3 inches above the mean sea level rise that is expected around the globe because of human-induced climate change.
Thermal expansion and the melting of land ice, such as the Greenland ice sheet, are expected to cause the global sea-level rise. The researchers projected the global sea-level rise of 10.2 inches based on thermal expansion alone. The contribution from the land ice melting was not assessed in this study due to uncertainty.
Considering that much of the metropolitan region of New York City is less than 16 feet above the mean sea level, with some parts of lower Manhattan only about 5 feet above the mean sea level, a rise of 8.3 inches in addition to the global mean rise would pose a threat to this region, especially if a hurricane or winter storm surge occurs, Yin said.
Potential flooding is just one example of coastal hazards associated with sea-level rise, Yin said, but there are other concerns as well. The submersion of low-lying land, erosion of beaches, conversion of wetlands to open water and increase in the salinity of estuaries all can affect ecosystems and damage existing coastal development.
Although low-lying Florida and Western Europe are often considered the most vulnerable to sea level changes, the northeast U.S. coast is particularly vulnerable because the Atlantic meridional overturning circulation (AMOC) is susceptible to global warming. The AMOC is the giant circulation in the Atlantic with warm and salty seawater flowing northward in the upper ocean and cold seawater flowing southward at depth. Global warming could cause an ocean surface warming and freshening in the high-latitude North Atlantic, preventing the sinking of the surface water, which would slow the AMOC.
Journal reference:
Yin et al. Model projections of rapid sea-level rise on the northeast coast of the United States. Nature Geoscience, March 15, 2009; DOI: 10.1038/ngeo462
Adapted from materials provided by Florida State University, via EurekAlert!, a service of AAAS.

Researchers Study Cave’s 'Breathing' For Better Climate Clues

2009-03-16T03:24:00.000-07:00

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ScienceDaily (Mar. 16, 2009) — A University of Arkansas researcher studying the way caves “breathe” is providing new insights into the process by which scientists study paleoclimates.

Katherine Knierim, a graduate student at the University of Arkansas, together with Phil Hays of the geosciences department and the U.S. Geological Survey and Erik Pollock of the University of Arkansas Stable Isotope Laboratory, are conducting close examinations of carbon cycling in an Ozark cave. Caves “breathe” in the sense that air flows in and out as air pressure changes.
The researchers have found that carbon dioxide pressures vary with external temperatures and ground cover, indicating a possible link between the carbon found in rock formations in the caves and seasonal changes. They presented their findings at a recent meeting of the American Geophysical Union.
The movement of carbon in cave systems is controlled by the concentration of carbon dioxide. When conditions are right, this carbon can be deposited as layers in stalagmites, stalactites and soda straws. These layers resemble the rings found in trees, except that they can date back millions of years, hold information about cave conditions.
“People have been using these formations as paleoclimate records,” Hays said. However, researchers make an assumption when they do so.
“The problem is that you have to assume you are getting even carbon and oxygen isotope exchange,” Knierim said. Isotopes, or atoms of the same type but with slightly different weights, are found in plants, animals, organic matter and rocks. Different types of material have unique “signatures,” or proportions of a particular atom at a particular atomic weight.
By looking at carbon isotope ratios in cave topsoils, the cave atmosphere and the stream within the cave, Knierim and her colleagues will be able to determine the different contributions of carbon sources to the formations. This will help scientists develop more accurate paleoclimate conditions from cave formations.
A greater knowledge of how carbon cycles through cave systems also will help scientists develop better methods for watershed management.
The researchers are in the geosciences department of the J. William Fulbright College of Arts and Sciences.
Adapted from materials provided by University of Arkansas, Fayetteville.

Ninth Warmest February For Globe, NOAA

2009-03-16T03:18:00.000-07:00

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ScienceDaily (Mar. 16, 2009) — The combined global land and ocean surface average temperature for February 2009 was the ninth warmest since records began in 1880, according to an analysis by NOAA’s National Climatic Data Center in Asheville, N.C.

The analyses in NCDC’s global reports are based on preliminary data, which are subject to revision. Additional quality control is applied to the data when later reports are received several weeks after the end of the month and as increased scientific methods improve NCDC’s processing algorithms.
Temperature Highlights – February
The combined global land and ocean surface temperature for February was 54.80 degrees F, 0.90 degree F above the 20th century mean of 53.9 degrees F, ranking as the ninth warmest on record.
Separately, the global land surface temperature was 39.38 degrees F, 1.58 degrees F above the 20th century mean of 37.8 degrees F.
The global ocean surface temperature of 61.25 degrees F ranked as eighth warmest on record and was 0.65 degree F above the 20th century mean of 60.6 degrees F.
Temperature Highlights – Boreal (Meteorological) Winter
The combined global land and ocean surface temperature for boreal winter (December-February) was 54.72 degrees F, 0.92 degree F above the 20th century mean of 53.8 degrees F and ranking eighth warmest.
Separately, the global land surface temperature was 39.31 degrees F, 1.51 degrees F above the 20th century mean of 37.8 degrees F, ranking as ninth warmest on record.
The global ocean surface temperature of 61.20 degrees F ranked as seventh warmest on record and was 0.70 degree F above the 20th century mean of 60.5 degrees F.
Global Highlights for February
Based on NOAA satellite observations of snow cover extent, 10.7 million square miles (27.7 million square kilometers) of Eurasia (Europe and Asia) were covered by snow in February 2009, which is 0.4 million square miles (1.1 million square kilometers) below the 1966-2009 average of 11.1 million square miles (28.8 million square kilometers).
Satellite-based snow cover extent for the Northern Hemisphere was 17.4 million square miles (45.0 million square kilometers) in February, which is 0.3 million square miles (0.9 million square kilometers) below the 1966-2009 average of 17.7 million square miles (45.9 million square kilometers).
Arctic sea ice coverage during February 2009 was at its fourth lowest February extent since satellite records began in 1979, according to the National Snow and Ice Data Center. Average ice extent during February was 5.7 million square miles (14.8 million square kilometers). The Arctic sea ice pack usually expands during the cold season, reaching a maximum in March, then contracts during the warm season, reaching a minimum in September.
Very hot, dry conditions affected southern Australia during the end of January and beginning of February. An intense heat wave February 6-8 resulted in a high temperature of 119.8 degrees F at Hopetoun, Victoria, Feb. 7, surpassing the previous record of 117.0 degrees F set in January 1939. This is a state record and perhaps the highest temperature ever recorded for such a southerly latitude. The hot, dry conditions contributed to the development of Australia’s deadliest wildfires in history.
China declared its highest level of emergency for eight provinces that were suffering from their worst drought in 50 years. The drought conditions, which began in November 2008, affected more than 4 million people and more than 24 million acres of crops.
A strong winter storm brought heavy snow to parts of the United Kingdom on February 2, disrupting transportation and bringing London to a virtual standstill. The event, in which up to 12 inches of snow fell in southeastern England, was the UK’s most widespread snow in 18 years, according to the UK Met Office.
Adapted from materials provided by National Oceanic And Atmospheric Administration.

Silica Algae Reveal How Ecosystems React To Climate Changes

2009-03-15T03:09:00.000-07:00

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ScienceDaily (Mar. 14, 2009) — A newly published dissertation by Linda Ampel from the Department of Physical Geography and Quaternary Geology at Stockholm University in Sweden examined how rapid climate changes during the most recent ice age affected ecosystems in an area in continental Europe.

Rapid and extensive climate changes have taken place on several occasions in the past. For example, the latest ice age (lasting from about 115,000 to 11,500 years ago) is characterized by several rapid and dramatic climate swings. These swings recurred in cycles of roughly 1,500 years and were originally discovered through studies of ice cores from Greenland in the early 1990s. These cycles started with an extremely rapid rise in temperatures, over just a few years or decades, of as much as 8-16o C over Greenland.
Linda Ampel studied how these rapid cycles in the climate affected ecosystems in an area in continental Europe. The study was based on analyses of sediment cores from an overgrown lake named Les Echets in eastern France and focuses on a time interval between 40,000 and 16,000 ago.
The findings are based on analyses of fossil silica algae, diatoms. Various species of diatoms prefer different water conditions relating to physical and chemical parameters such as temperature, salinity, access to nutrients, light, water depth, or available types of places to grow. These parameters, in turn, are affected by climate. Different species of diatoms can therefore indicate how the water environment changed as a consequence of the climate in the past.
Diatom analyses of the environmental archive from Les Echets, together with further analyses of chemical and biological parameters such as content of organic material and pollen grains from trees and other plants preserved in the lake, show that the ecosystems in the lake and its surroundings underwent marked changes during the latest ice age as a consequence of these 1,500-year cycles. The adaptation of the ecosystems prompted by the recurring warm periods took place as quickly as within 50 to 200 years.
“These findings show that ecosystems have changed rapidly in reaction to climate changes in the past, which indicates that quick adaptations could also take place in the future as a consequence of global warming, for instance,” says Linda Ampel.
Adapted from materials provided by Vetenskapsrådet (The Swedish Research Council), via AlphaGalileo.

Wind Shifts May Stir Carbon Dioxide From Antarctic Depths, Amplifying Global Warming

2009-03-14T01:04:00.001-07:00

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ScienceDaily (Mar. 13, 2009) — Natural releases of carbon dioxide from the Southern Ocean due to shifting wind patterns could have amplified global warming at the end of the last ice age--and could be repeated as manmade warming proceeds, a new paper in the journal Science suggests.

Many scientists think that the end of the last ice age was triggered by a change in Earth's orbit that caused the northern part of the planet to warm. This partial climate shift was accompanied by rising levels of the greenhouse gas CO2, ice core records show, which could have intensified the warming around the globe. A team of scientists at Columbia University's Lamont-Doherty Earth Observatory now offers one explanation for the mysterious rise in CO2: the orbital shift triggered a southward displacement in westerly winds, which caused heavy mixing in the Southern Ocean around Antarctica, pumping dissolved carbon dioxide from the water into the air.
"The faster the ocean turns over, the more deep water rises to the surface to release CO2," said lead author Robert Anderson, a geochemist at Lamont-Doherty. "It's this rate of overturning that regulates CO2 in the atmosphere." In the last 40 years, the winds have shifted south much as they did 17,000 years ago, said Anderson. If they end up venting more CO2 into the air, manmade warming underway now could be intensified.
Scientists have been studying the oceans for more than 25 years to understand their influence on CO2 levels and the glacial cycles that have periodically heated and chilled the planet for more than 600,000 years. Ice cores show that the ends of other ice ages also were marked by rises in CO2.
Two years ago, J.R. Toggweiler, a scientist at the National Oceanic and Atmospheric Administration (NOAA), proposed that westerly winds in the Southern Ocean around Antarctica may have undergone a major shift at the end of the last ice age. This shift would have raised more CO2-rich deep water to the surface, and thus amplified warming already taking place due to the earth's new orbital position. Anderson and his colleagues are the first to test that theory by studying sediments from the bottom of the Southern Ocean to measure the rate of overturning.
The scientists say that changes in the westerlies may have been triggered by two competing events in the northern hemisphere about 17,000 years ago. The earth's orbit shifted, causing more sunlight to fall in the north, partially melting the ice sheets that then covered parts of the United States, Canada and Europe. Paradoxically, the melting may also have spurred sea-ice formation in the North Atlantic Ocean, creating a cooling effect there. Both events would have caused the westerly winds to shift south, toward the Southern Ocean. The winds simultaneously warmed Antarctica and stirred the waters around it. The resulting upwelling of CO2 would have caused the entire globe to heat.
Anderson and his colleagues measured the rate of upwelling by analyzing sediment cores from the Southern Ocean. When deep water is vented, it brings not only CO2 to the surface but nutrients. Phytoplankton consume the extra nutrients and multiply.
In the cores, Anderson and his colleagues say spikes in plankton growth between roughly 17,000 years ago and 10,000 years ago indicate added upwelling. By comparing those spikes with ice core records, the scientists realized the added upwelling coincided with hotter temperatures in Antarctica as well as rising CO2 levels.
In the same issue of Science, Toggweiler writes a column commenting on the work. "Now I think this really starts to lock up how the CO2 changed globally," he said in an interview. "Here's a mechanism that can explain the warming of Antarctica and the rise in CO2. It's being forced by the north, via this change in the winds."
At least one model supports the evidence. Richard Matear, a researcher at Australia's Commonwealth Scientific and Industrial Research Organisation, describes a scenario in which winds shift south and produce an increase in CO2 venting in the Southern Ocean. Plants, which incorporate CO2 during photosynthesis, are unable to absorb all the added nutrients, causing atmospheric CO2 to rise.
Some other climate models disagree. In those used by the Intergovernmental Panel on Climate Change, the westerly winds do not simply shift north-south. "It's more complicated than this," said Axel Timmermann, a climate modeler at the University of Hawaii. Even if the winds did shift south, Timmermann argues, upwelling in the Southern Ocean would not have raised CO2 levels in the air. Instead, he says, the intensification of the westerlies would have increased upwelling and plant growth in the Southeastern Pacific, and this would have absorbed enough atmospheric CO2 to compensate for the added upwelling in the Southern Ocean.
"Differences among model results illustrate a critical need for further research," said Anderson. These, include "measurements that document the ongoing physical and biogeochemical changes in the Southern Ocean, and improvements in the models used to simulate these processes and project their impact on atmospheric CO2 levels over the next century."
Anderson says that if his theory is correct, the impact of upwelling "will be dwarfed by the accelerating rate at which humans are burning fossil fuels." But, he said, "It could well be large enough to offset some of the mitigation strategies that are being proposed to counteract rising CO2, so it should not be neglected."
In addition to Anderson, the paper was coauthored by Simon Nielsen of Florida State University, and five Lamont-Doherty researchers: Shahla Ali, Louisa Bradtmiller, Martin Fleisher, Brenton Anderson and Lloyd Burckle. The study was funded by NOAA, the National Science Foundation, Norwegian Research Council and Norwegian Polar Institute.
Journal reference:
. Wind-Driven Upwelling in the Southern Ocean and the Deglacial Rise in Atmospheric CO2. Science, March 13, 2009
Adapted from materials provided by The Earth Institute at Columbia University, via EurekAlert!, a service of AAAS.

New Method For Monitoring Volcanoes

2009-03-13T13:46:00.000-07:00

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ScienceDaily (Mar. 13, 2009) — Seventeen of the world’s most active volcanoes have been supplied with monitoring equipment from Chalmers University of Technology in Sweden to measure their emission of sulphur dioxide. The measurement results will be used to make it easier to predict volcano eruptions, and they can also be used to improve today’s climate models.

One of the Chalmers researchers who developed the monitoring equipment is Mattias Johansson, who recently defended his doctoral dissertation in the subject.
The most active volcanoes in the world have special observatories that monitor them in order to be able to sound the alarm and evacuate people in the vicinity if an eruption threatens. These observatories keep track of several parameters, primarily seismic activity. Now 17 observatories have received a new parameter that facilitates their work – the volcanoes’ emissions of sulphur dioxide.
“Increasing gas emissions may indicate that magma is rising inside the volcano,” says Mattias Johansson at the Department of Radio and Space Science at Chalmers. “If this information is added to the other parameters, better risk estimates can be made at the observatories.”
The equipment he has been working with measures the total amount of gas emitted, whereas most other methods for metering gas can only indicate the gas concentration at a particular point. This is made possible by placing two or more metering instruments in different places around the volcano and then aggregating the information they gather.
Much of the Chalmers researchers’ work has involved making the equipment sufficiently automatic, robust, and energy-efficient for use in the inhospitable environment surrounding volcanoes, in poor countries with weak infrastructure.
“I have primarily been working with the software required for processing and presenting the measurement results,” says Mattias Johansson. “Among other things, I have created a program that analyzes the data collected, calculates the outward flow of gas, and presents the information as a simple graph on a computer screen that the observatory staff need only glance at to find out how much sulphur dioxide the volcano is emitting at any particular time.”
He has also participated in the installation of the equipment on two of the volcanoes, Aetna in Italy and San Cristobal in Nicaragua. In Project Novac, which his research is part of, a total of 20 volcanoes will be provided with monitoring equipment from Chalmers.
It will also be possible to improve global climate models when the Chalmers researchers receive continuous reports about how much sulphur dioxide is emitted by the 20 most active volcanoes.
“Sulphur dioxide is converted in the atmosphere to sulphate particles, and these particles need to be factored into climate models if those models are to be accurate,” says Associate Professor Bo Galle, who directed the dissertation. “Volcanoes are an extremely important source of sulphur dioxide. Aetna alone, for instance, releases roughly ten times more sulphur dioxide than all of Sweden does.”
The methods that Mattias Johansson has devised can moreover be used to measure the total emissions of air pollutants from an entire city. China has already purchased equipment that they are now using to study the pollution situation in the megacity Beijing.
Adapted from materials provided by The Swedish Research Council, via AlphaGalileo.

Coral Reefs May Start Dissolving When Atmospheric Carbon Dioxide Doubles

2009-03-11T04:43:00.000-07:00

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ScienceDaily (Mar. 10, 2009) — Rising carbon dioxide in the atmosphere and the resulting effects on ocean water are making it increasingly difficult for coral reefs to grow, say scientists. A study to be published online March 13, 2009 in Geophysical Research Letters by researchers at the Carnegie Institution and the Hebrew University of Jerusalem warns that if carbon dioxide reaches double pre-industrial levels, coral reefs can be expected to not just stop growing, but also to begin dissolving all over the world.

The impact on reefs is a consequence of both ocean acidification caused by the absorption of carbon dioxide into seawater and rising water temperatures. Previous studies have shown that rising carbon dioxide will slow coral growth, but this is the first study to show that coral reefs can be expected to start dissolving just about everywhere in just a few decades, unless carbon dioxide emissions are cut deeply and soon.
"Globally, each second, we dump over 1000 tons of carbon dioxide into the atmosphere and, each second, about 300 tons of that carbon dioxide is going into the oceans," said co-author Ken Caldeira of the Carnegie Institution's Department of Global Ecology, testifying to the U.S. House of Representatives Subcommittee on Insular Affairs, Oceans and Wildlife of the Committee on Natural Resources on February 25, 2009. "We can say with a high degree of certainty that all of this CO2 will make the oceans more acidic – that is simple chemistry taught to freshman college students."
The study was designed determine the impact of this acidification on coral reefs. The research team, consisting of Jacob Silverman, Caldeira, and Long Cao of the Carnegie Institution as well as Boaz Lazar and Jonathan Erez from The Hebrew University of Jerusalem, used field data from coral reefs to determine the effects of temperature and water chemistry on coral calcification rates. Armed with this information, they plugged the data into a computer model that calculated global seawater temperature and chemistry at different atmospheric levels of CO2 ranging from the pre-industrial value of 280 ppm (parts per million) to 750 ppm. The current atmospheric concentration is over 380 ppm, and is rapidly rising due to human-caused emissions, primarily through the burning of fossil fuels.
Based on the model results for more than 9,000 reef locations, the researchers determined that at the highest concentration studied, 750 ppm, acidification of seawater would reduce calcification rates of three quarters of the world's reefs to less than 20% of pre-industrial rates. Field studies suggest that at such low rates, coral growth would not be able to keep up with dissolution and other natural as well as manmade destructive processes attacking reefs.
Prospects for reefs are even gloomier when the effects of coral bleaching are included in the model. Coral bleaching refers to the loss of symbiotic algae that are essential for healthy growth of coral colonies. Bleaching is already a widespread problem, and high temperatures are among the factors known to promote bleaching. According to their model the researchers calculated that under present conditions 30% of reefs have already undergone bleaching and that at CO2 levels of 560 ppm (twice pre-industrial levels) the combined effects of acidification and bleaching will reduce the calcification rates of all the world's reefs by 80% or more. This lowered calcification rate will render all reefs vulnerable to dissolution, without even considering other threats to reefs, such as pollution.
"Our fossil-fueled lifestyle is killing off coral reefs," says Caldeira. "If we don't change our ways soon, in the next few decades we will destroy what took millions of years to create."
"Coral reefs may be the canary in the coal mine," he adds. "Other major pieces of our planet may be similarly threatened because we are using the atmosphere and oceans as dumps for our CO2 pollution. We can save the reefs if we decide to treat our planet with the care it deserves. We need to power our economy with technologies that do not dump carbon dioxide into the atmosphere or oceans."
Journal reference:
Silverman, J., B. Lazar, L. Cao, K. Caldeira, and J. Erez. Coral reefs may start dissolving when atmospheric CO2 doubles. Geophys. Res. Lett., 2009; DOI: 10.1029/2008GL036282
Adapted from materials provided by Carnegie Institution, via EurekAlert!, a service of AAAS.

Rising Sea Levels Set To Have Major Impacts Around The World

2009-03-11T03:32:00.001-07:00

SOURCE

ScienceDaily (Mar. 11, 2009) — Research presented March 10 at the International Scientific Congress on Climate Change in Copenhagen shows that the upper range of sea level rise by 2100 could be in the range of about one meter, or possibly more. In the lower end of the spectrum it looks increasingly unlikely that sea level rise will be much less than 50 cm by 2100.

This means that if emissions of greenhouse gases is not reduced quickly and substantially, even the best case scenario will hit low lying coastal areas housing one in ten humans on the planet hard.
Dr John Church of the Centre for Australian Weather and Climate Research, Hobart, Tasmania, Australia and the lead speaker in the sea level session, told the conference, "The most recent satellite and ground based observations show that sea-level rise is continuing to rise at 3 mm/yr or more since 1993, a rate well above the 20th century average. The oceans are continuing to warm and expand, the melting of mountain glacier has increased and the ice sheets of Greenland and Antarctica are also contributing to sea level rise."
New insights reported include the loss of ice from the Antarctic and Greenland Ice Sheets. "The ice loss in Greenland has accelerated over the last decade. The upper range of sea level rise by 2100 might be above 1m or more on a global average, with large regional differences depending where the source of ice loss occurs", says Konrad Steffen, Director of the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado, Boulder and co-chair of the congress session on sea level rise.
The last assessment report from the IPCC from 2007 projected a sea level rise of 18 - 59 centimeter. However the report also clearly stated that not all factors contributing to sea level rise could be calculated at that time. The uncertainty was centered on the ice sheets, how they react to the effects of a warmer climate and how they interact with the oceans, explains Eric Rignot, Professor of Earth System Science at the University of California Irvine and Senior Research Scientist at NASA's Jet Propulsion Laboratory.
"The numbers from the last IPCC are a lower bound because it was recognized at the time that there was a lot of uncertainty about ice sheets. The numerical models used at the time did not have a complete representation of outlet glaciers and their interactions with the ocean. The results gathered in the last 2-3 years show that these are fundamental aspects that cannot be overlooked. As a result of the acceleration of outlet glaciers over large regions, the ice sheets in Greenland and Antarctica are already contributing more and faster to sea level rise than anticipated. If this trend continues, we are likely to witness sea level rise one meter or more by year 2100", he says.
"Unless we undertake urgent and significant mitigation actions, the climate could cross a threshold during the 21st century committing the world to a sea level rise of metres", said John Church.
"Measurements around the world show that sea level has risen almost 20 centimeters since 1880," explains Professor Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research, who will give the plenary speech on sea level rise at the congress. These data also reveal that the rate of sea level rise is closely linked to temperature: sea level rises faster the warmer it gets. "If sea level keeps rising at a constant pace, we will end up in the middle of that 18-59 cm IPCC range by 2100," says Rahmstorf. "But based on past experience I expect that sea level rise will accelerate as the planet gets hotter."
The impacts of sea level rise - even in the lower ranges of the current predictions - looks to be severe. Approximately ten percent of the worlds population - 600 million people - live in low lying areas in danger of being flooded. A previously released study led by John Church, shows that even a modest sea level rise of 50 centimeters will result in a major increase in the number of coastal flooding events.
"Our study centered on Australia showed that coastal flooding events that today we expect only once every hundred years will happen several times a year by 2100", says John Church.
John Church also brings new results of the current sea level rise to the congress, "Sea level is currently rising at a rate that is above any of the model projections of 18 to 59 cm".
"Different groups may come to slightly different projections, but differences in the details of the projections should not cloud the overall picture where even the lower end of the projections looks to have very serious effects," says Konrad Steffen.
1. The rising tide: assessing the risks od climate change and human settlements in low elevation costal zones. Gordon McGranahan, Deborah Balk, and Bridget Anderson; Environment and Urbanization, Apr 2007; vol. 19: pp. 17-37.
Adapted from materials provided by University of Copenhagen.

Melting Glaciers May Release DDT And Contaminate Antarctic Environment

2008-05-27T22:33:00.001-07:00

Source:

http://www.sciencedaily.com/releases/2008/05/080526153152.htm

ScienceDaily (May 27, 2008) — In an unexpected consequence of climate change, scientists are raising the possibility that glacial melting is releasing large amounts of the banned pesticide DDT, which is contaminating the environment in Antarctica.

The study is scheduled for the June 1 issue of ACS’ bi-weekly journal Environmental Science & Technology.
In the study, Heidi N. Geisz and colleagues estimate that up to 2.0-8.8 pounds of DDT are released into coastal waters annually along the Western Antarctic Ice Sheet from glacial meltwater. The researchers point out that DDT reaches Antarctica by long-range atmospheric transport in snow, and then gets concentrated in the food chain.
DDT has been banned in the northern hemisphere and has been regulated worldwide since the 1970s. Geisz found, however, that DDT levels in the Adelie penguin have been unchanged since the 1970s, despite an 80 percent reduction in global use.
Global warming may explain that contradiction, they say. As the annual winter temperature on the Antarctic Peninsula has increased by about 10 degrees Fahrenheit in the last 30 years, glaciers have retreated. The possibility that glacial meltwater has contaminated Antarctic organisms with DDT, the study says, “has compelling consequences” if global warming should continue and intensify.

Fausto Intilla - www.oloscience.com

Scorched Earth Millenium Map Shows 'Fire Scars'

2008-05-27T22:30:00.000-07:00

Source:

http://www.sciencedaily.com/releases/2008/05/080522093333.htm

ScienceDaily (May 27, 2008) — A geographer from the University of Leicester has produced for the first time a map of the scorched Earth for every year since the turn of the Millennium.

Dr Kevin Tansey, of the Department of Geography, a leading scientist in an international team, created a visual impression of the fire scars on our planet between 2000 and 2007. The work was funded by the Joint Research Centre of the European Commission.
The map reveals that between 3.5 and 4.5 million km2 of vegetation burns on an annual basis. This is an area equivalent to the European Union (EU27) and larger than the country of India that is burnt every year.
The information is vital for scientists and agencies involved in monitoring global warming, measuring and understanding pollutants in the atmosphere, managing forests and controlling fire and even for predicting future fire occurrence.
Dr Tansey, a Lecturer in Remote Sensing at the University of Leicester, said: "We have produced, for the first time, a global data base and map of the occurrence of fire scars covering the period 2000-2007. Prior to this development, data were only available for the year 2000. With seven years of data, it is not possible to determine if there is an increasing trends in the occurrence of fire, but we have significant year-to-year differences, of the order of 20%, in the area that is burnt.
"The work was undertaken with colleagues from the Joint Research Centre of the European Commission (Italy) and the Université catholique de Louvain (Belgium).
"This unique data set is in much demand by a large community of scientists interested in climate change, vegetation monitoring, atmospheric chemistry and carbon storage and flows.
"We have used the VEGETATION instrument onboard the SPOT European satellite, which collects reflected solar energy from the Earth's surface, providing global coverage on almost a daily basis.
"When vegetation burns the amount of reflected energy is altered, long enough for us to make an observation of the fire scar. Supercomputers located in Belgium were used to process the vast amounts of satellite data used in the project. At the moment, we have users working towards predicting future fire occurrence and fire management issues in the Kruger Park in southern Africa".
"The majority of fires occur in Africa. Large swathes of savannah grasslands are cleared every year, up to seven times burnt in the period 2000-2007 (see Figure 1). The system is sustainable because the grass regenerates very quickly during the wet season. From a carbon perspective, there is a net balance due to the regenerating vegetation acting as a carbon sink. Fires in forests are more important as the affected area becomes a carbon source for a number of years.
"The forest fires last summer in Greece and in Portugal a couple of years back, remind us that we need to understand the impact of fire on the environment and climate to manage the vegetation of the planet more effectively. Probably 95% of all vegetation fires have a human source; crop stubble burning, forest clearance, hunting, arson are all causes of fire across the globe. Fire has been a feature of the planet in the past and under a scenario of a warmer environment will certainly be a feature in the future".
The project was funded by the European Commission, through DG Joint Research Centre.

Fausto Intilla - www.oloscience.com

Hot Climate Could Shut Down Plate Tectonics

2008-05-13T12:21:00.000-07:00

Source:

http://www.sciencedaily.com/releases/2008/05/080512135102.htm

ScienceDaily (May 13, 2008) — A new study of possible links between climate and geophysics on Earth and similar planets finds that prolonged heating of the atmosphere can shut down plate tectonics and cause a planet's crust to become locked in place.

"The heat required goes far beyond anything we expect from human-induced climate change, but things like volcanic activity and changes in the sun's luminosity could lead to this level of heating," said lead author Adrian Lenardic, associate professor of Earth science at Rice University. "Our goal was to establish an upper limit of naturally generated climate variation beyond which the entire solid planet would respond."
Lenardic said the research team wanted to better understand the differences between the Earth and Venus and establish the potential range of conditions that could exist on Earth-like planets beyond the solar system. The team includes Lenardic and co-authors Mark Jellinek of the University of British Columbia in Vancouver and Louis Moresi of Monash University in Clayton, Australia. The research is available online from the journal Earth and Planetary Science Letters.
The findings may explain why Venus evolved differently from Earth. The two planets are close in size and geological makeup, but Venus' carbon dioxide-rich atmosphere is almost 100 times more dense than the Earth's and acts like a blanket. As a result, Venus' surface temperature is hotter than that of even Mercury, which is twice as close to the sun.
The Earth's crust -- along with carbon trapped on the oceans' floors -- gets returned to the interior of the Earth when free-floating sections of crust called tectonic plates slide beneath one another and return to the Earth's mantle. The mantle is a flowing layer of rock that extends from the planet's outer core, about 1,800 miles below the surface, to within about 30 miles of the surface, just below the crust.
"We found the Earth's plate tectonics could become unstable if the surface temperature rose by 100 degrees Fahrenheit or more for a few million years," Lenardic said. "The time period and the rise in temperatures, while drastic for humans, are not unreasonable on a geologic scale, particularly compared to what scientists previously thought would be required to affect a planet's geodynamics."
Conventional wisdom holds that plate tectonics is both stable and self-correcting, but that view relies on the assumption that excess heat from the Earth's mantle can efficiently escape through the crust. The stress generated by flowing mantle helps keep tectonic plates in motion, and the mantle can become less viscous if it heats up. The new findings show that prolonged heating of a planet's crust via rising atmospheric temperatures can heat the deep inside of the planet and shut down tectonic plate movement.
"We found a corresponding spike in volcanic activity could accompany the initial locking of the tectonic plates," Lenardic said. "This may explain the large percentage of volcanic plains that we find on Venus."
Venus' surface, which shows no outward signs of tectonic activity, is bone dry and heavily scarred with volcanoes. Scientists have long believed that Venus' crust, lacking water to help lubricate tectonic plate boundaries, is too rigid for active plate tectonics.
Lenardic said one of the most significant findings in the new study is that the atmospheric heating needed to shut down plate tectonics is considerably less than the critical temperature beyond which free water could exist on the Earth's surface.
"The water doesn't have to boil away for irrevocable heating to occur," Lenardic said. "The cycle of heating can be kicked off long before that happens. All that's required is enough prolonged surface heating to cause a feedback loop in the planet's mantle convection cycle."
The research was supported by the National Science Foundation and the Canadian Institute for Advanced Research.

Fausto Intilla - www.oloscience.com

Solar Variability: Striking A Balance With Climate Change

2008-05-13T03:11:00.000-07:00

Source:

http://www.sciencedaily.com/releases/2008/05/080512120523.htm

ScienceDaily (May 12, 2008) — The sun has powered almost everything on Earth since life began, including its climate. The sun also delivers an annual and seasonal impact, changing the character of each hemisphere as Earth's orientation shifts through the year. Since the Industrial Revolution, however, new forces have begun to exert significant influence on Earth's climate.
"For the last 20 to 30 years, we believe greenhouse gases have been the dominant influence on recent climate change," said Robert Cahalan, climatologist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
For the past three decades NASA scientists have investigated the unique relationship between the sun and Earth. Using space-based tools, like the Solar Radiation and Climate Experiment (SORCE), they have studied how much solar energy illuminates Earth, and explored what happens to that energy once it penetrates the atmosphere. The amount of energy that reaches Earth's outer atmosphere is called the total solar irradiance. Total solar irradiance is variable over many different timescales, ranging from seconds to centuries due to changes in solar activity.
The sun goes through roughly an 11-year cycle of activity, from stormy to quiet and back again. Solar activity often occurs near sunspots, dark regions on the sun caused by concentrated magnetic fields. The solar irradiance measurement is much higher during solar maximum, when sunspot cycle and solar activity is high, versus solar minimum, when the sun is quiet and there are usually no sunspots.
"The fluctuations in the solar cycle impacts Earth's global temperature by about 0.1 degree Celsius, slightly hotter during solar maximum and cooler during solar minimum," said Thomas Woods, solar scientist at the University of Colorado in Boulder. "The sun is currently at its minimum, and the next solar maximum is expected in 2012."
Using SORCE, scientists have learned that about 1,361 watts per square meter of solar energy reaches Earth's outermost atmosphere during the sun's quietest period. But when the sun is active, 1.3 watts per square meter (0.1 percent) more energy reaches Earth. "This TSI measurement is very important to climate models that are trying to assess Earth-based forces on climate change," said Cahalan.
Over the past century, Earth's average temperature has increased by approximately 0.6 degrees Celsius (1.1 degrees Fahrenheit). Solar heating accounts for about 0.15 C, or 25 percent, of this change, according to computer modeling results published by NASA Goddard Institute for Space Studies researcher David Rind in 2004. Earth's climate depends on the delicate balance between incoming solar radiation, outgoing thermal radiation and the composition of Earth's atmosphere. Even small changes in these parameters can affect climate. Around 30 percent of the solar energy that strikes Earth is reflected back into space. Clouds, atmospheric aerosols, snow, ice, sand, ocean surface and even rooftops play a role in deflecting the incoming rays. The remaining 70 percent of solar energy is absorbed by land, ocean, and atmosphere.
"Greenhouse gases block about 40 percent of outgoing thermal radiation that emanates from Earth," Woods said. The resulting imbalance between incoming solar radiation and outgoing thermal radiation will likely cause Earth to heat up over the next century, accelerating the melting polar ice caps, causing sea levels to rise and increasing the probability of more violent global weather patterns.
Non-Human Influences on Climate Change
Before the Industrial Age, the sun and volcanic eruptions were the major influences on Earth's climate change. Earth warmed and cooled in cycles. Major cool periods were ice ages, with the most recent ending about 11,000 years ago.
"Right now, we are in between major ice ages, in a period that has been called the Holocene,” said Cahalan. “Over recent decades, however, we have moved into a human-dominated climate that some have termed the Anthropocene. The major change in Earth's climate is now really dominated by human activity, which has never happened before."
The sun is relatively calm compared to other stars. "We don't know what the sun is going to do a hundred years from now," said Doug Rabin, a solar physicist at Goddard. "It could be considerably more active and therefore have more influence on Earth's climate."
Or, it could be calmer, creating a cooler climate on Earth similar to what happened in the late 17th century. Almost no sunspots were observed on the sun's surface during the period from 1650 to 1715. This extended absence of solar activity may have been partly responsible for the Little Ice Age in Europe and may reflect cyclic or irregular changes in the sun's output over hundreds of years. During this period, winters in Europe were longer and colder by about 1 C than they are today.
Since then, there seems to have been on average a slow increase in solar activity. Unless we find a way to reduce the amount of greenhouse gases we put into the atmosphere, such as carbon dioxide from fossil fuel burning, the solar influence is not expected to dominate climate change. But the solar variations are expected to continue to modulate both warming and cooling trends at the level of 0.1 to 0.2 degrees Celsius (0.18 to 0.26 Fahrenheit) over many years.
Future Measurements of Solar Variability
For three decades, a suite of NASA and European Space Agency satellites have provided scientists with critical measurements of total solar irradiance. The Total Irradiance Monitor, also known as the TIM instrument, was launched in 2003 as part of the NASA’s SORCE mission, and provides irradiance measurements with state-of-the-art accuracy. TIM has been rebuilt as part of the Glory mission, scheduled to launch in 2009. Glory's TIM instrument will continue an uninterrupted 30-year record of solar irradiance measurements and will help researchers better understand the sun's direct and indirect effects on climate. Glory will also collect data on aerosols, one of the least understood pieces of the climate puzzle.

Fausto Intilla - www.oloscience.com

Coherent Description Of Earth's Inaccessible Interior Clarifies Mantle Motion

2008-05-04T11:04:00.000-07:00

Source:

http://www.sciencedaily.com/releases/2008/05/080501154212.htm

ScienceDaily (May 4, 2008) — A new model of inner Earth constructed by Arizona State University researchers pulls past information and hypotheses into a coherent story to clarify mantle motion.

"The past maybe two or three years there have been a lot of papers in Science and Nature about the deep mantle from seismologists and mineral physicists and it's getting really confusing because there are contradictions amongst the different papers," says Ed Garnero, seismologist and an associate professor in Arizona State University's School of Earth and Space Exploration.
"But we've discovered that there is a single framework that is compatible with all these different findings," he adds.
Garnero partnered with geodynamicist and assistant professor Allen McNamara, also in the School of Earth and Space Exploration in ASU's College of Liberal Arts and Sciences, to synthesize the information for their paper to be published in the May 2 issue of Science.
"Our goal was to bring the latest seismological and dynamical results together to put some constraints on the different hypotheses we have for the mantle. If you Google 'mantle' you'll see 20 different versions of what people are teaching," explains McNamara.
According to the ASU scientists, all this recent research of the past few years fits into a single story. But what is that story? Is it a complicated and exceedingly idiosyncratic story or is it a straightforward simple framework?
"In my opinion," explains Garnero, "it's simple. It doesn't really appeal to anything new; it just shows how all those things can fit together."
The pair paints a story for a chemically complex inner earth, a model that sharply contrasts the heavily relied upon paradigm of the past few decades that the mantle is all one thing and well mixed. The original model was composed of simple concentric spheres representing the core, mantle and crust -- but the inner Earth isn't that simple.
What lies beneath
Earth is made up of several layers. Its skin, the crust, extends to a depth of about 40 kilometers (25 miles). Below the crust is the mantle area, which continues to roughly halfway to the center of Earth. The mantle is the thick layer of silicate rock surrounding the dense, iron-nickel core, and it is subdivided into the upper and lower mantle, extending to a depth of about 2,900 km (1,800 miles). The outer core is beneath that and extends to 5,150 km (3,200 mi) and the inner core to about 6,400 km (4,000 mi).
The inner Earth is not a static storage space of the geologic history of our planet -- it is continuously churning and changing. How a mantle convects and how the plates move is very different depending on whether the mantle is isochemical (chemically homogenous made entirely of only one kind of material) or heterogeneous, composed of different kinds of compounds.
Garnero and McNamara's framework is based upon the assumption that the Earth's mantle is not isochemical. Garnero says new data supports a mantle that consists of more than one type of material.
"Imagine a pot of water boiling. That would be all one kind of composition. Now dump a jar of honey into that pot of water. The honey would be convecting on its own inside the water and that's a much more complicated system," McNamara explains.
Observations, modeling and predictions have shown that the deepest mantle is complex and significantly more anomalous than the rest of the lower mantle. To understand this region, seismologists analyze tomographic images constructed from seismic wave readings. For 25 years they have been detecting differences in the speeds of waves that go through the mantle.
This difference in wave speeds provides an "intangible map" of the major boundaries inside the mantle -- where hot areas are, where cold areas are, where there are regions that might be a different composition, etc. The areas with sluggish wave speeds seem to be bounded rather abruptly by areas with wave speeds that are not sluggish or delayed. An abrupt change in wave speed means that something inside the mantle has changed.
If the mantle is all the same material, then researchers shouldn't be observing the boundary between hot and cold in the mantle as a super sharp edge and the temperature anomalies should also be more spread out. The abrupt change in velocity was noticeable, yet they didn't know what caused it.
Garnero and McNamara believe that the key aspect to this story is the existence of thermo-chemical piles. On each side of the Earth there are two big, chemically distinct, dense "piles" of material that are hundreds of kilometers thick -- one beneath the Pacific and the other below the Atlantic and Africa. These piles are two nearly antipodal large low shear velocity provinces situated at the base of Earth's mantle.
"You can picture these piles like peanut butter. It is solid rock but rock under very high pressures and temperatures become soft like peanut butter so any stresses will cause it to flow," says McNamara.
Recently mineral physicists discovered that under high pressure the atoms in the rocks go through a phase transition, rearranging themselves into a tighter configuration.
In these thermo-chemical piles the layering is consistent with a new high pressure phase of the most abundant lower mantle mineral called post-perovskite, a material that exists specifically under high pressures that cause new arrangements of atoms to be formed.
Perovskite is a specific arrangement of silicon and magnesium and iron atoms.
"At a depth a few hundred kilometers above the core, the mineral physicists tell us that the rocks' atoms can go into this new structure and it should happen abruptly and that's consistent with the velocity discontinuities that the seismologists have been seeing for decades," says Garnero.
These thick piles play a key role in the convection currents. Ultra-low velocity zones live closest to the edges of the piles because that's the hottest regions of the mantle due to the currents that go against the pile walls as they bring the heat up from the core. Off their edges exist instability upwellings that turn out to be the plumes that feed hot spots such as Hawaii, Iceland and the Galapagos.
"We observe the motions of plate tectonics very well, but we can't fully understand how the mantle is causing these motions until we better understand how the mantle itself is convecting," says McNamara. "The piles dictate how the convective cycles happen, how the currents circulate. If you don't have piles then convection will be completely different."
Adapted from materials provided by Arizona State University, via EurekAlert!, a service of AAAS.

Fausto Intilla - www.oloscience.com