Northern Lights Glimmer With Unexpected Trait

Source:

http://www.sciencedaily.com/releases/2008/04/080425123355.htm

ScienceDaily (Apr. 26, 2008) — An international team of scientists has detected that some of the glow of Earth's aurora is polarized, an unexpected state for such emissions. Measurements of this newfound polarization in the Northern Lights may provide scientists with fresh insights into the composition of Earth's upper atmosphere, the configuration of its magnetic field, and the energies of particles from the Sun, the researchers say.
If observed on other planets, the phenomenon might also give clues to the shape of the Sun's magnetic field as it curls around other bodies in the solar system.
When a beam of light is polarized, its electromagnetic waves share a common orientation, say, aligned vertically, or at some other angle. Until now, scientists thought that light from energized atoms and molecules in planetary upper atmospheres could not be polarized. The reason is simple: in spite of the low number of particles at the altitudes concerned (above 100 kilometers (60 miles)), there are still numerous collisions between molecules and gas atoms. Those collisions depolarize the emitted light.
Fifty years ago, an Australian researcher, Robert Duncan, claimed to observe what looked like polarization of auroral light, but other scientists found that single observation unconvincing.
To revisit the question, Jean Lilensten of the Laboratory of Planetology of Grenoble, France, and his colleagues studied auroral light with a custom-made telescope during the winters of 2006-2007 and 2007-2008. They made their observations from Svalbard Island, Norway, which is in the polar region, at a latitude of 79° north.
At the north and south magnetic poles, many charged particles in the solar wind --a flow of electrically charged matter from the Sun--are captured by the planet's field and forced to plunge into the atmosphere. The particles strike atmospheric gases, causing light emissions.
Lilensten and his colleagues observed weak polarization of a red glow that radiates at an altitude of 220 kilometers (140 miles). The glow results from electrons hitting oxygen atoms. The scientists had suspected that such light might be polarized because Earth's magnetic field at high latitudes funnels the electrons, aligning the angles at which they penetrate the atmosphere.
The finding of auroral polarization "opens a new field in planetology," says Lilensten, who is the lead author of the study. He and his colleagues reported their results on 19 April in Geophysical Research Letters, a publication of the American Geophysical Union, or AGU.
Fluctuations in the polarization measurements can reveal the energy of the particles coming from the Sun when they enter Earth's atmosphere, Lilensten notes. The intensity of the polarization gives clues to the composition of the upper atmosphere, particularly with regard to atomic oxygen.
Because polarization is strongest when the telescope points perpendicularly to the magnetic field lines, the measurements also provide a way to determine magnetic field configurations, Lilensten adds. That could prove especially useful as astronomers train their telescopes on other planetary atmospheres. If polarized emissions are observed there as well, the measurements may enable scientists to understand how the Sun's magnetic field is distorted by obstacles such as the planets Venus and Mars, which lack intrinsic magnetic fields.
Journal reference: Lilensten, J., J. Moen, M. Barthélemy, R. Thissen, C. Simon, D. A. Lorentzen, O. Dutuit, P. O. Amblard, and F. Sigernes (2008), Polarization in aurorae: A new dimension for space environments studies, Geophys. Res. Lett., 35, L08804, doi:10.1029/2007GL033006.
Adapted from materials provided by American Geophysical Union.

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Mystery Of Ancient Supercontinent's Demise Revealed

Source:

http://www.sciencedaily.com/releases/2008/04/080423185112.htm

ScienceDaily (Apr. 24, 2008) — In a paper published in Geophysical Journal International, Dr Graeme Eagles from the Earth Sciences Department at Royal Holloway, University of London, reveals how one of the largest continents ever to exist met its demise.

Gondwana was a ‘supercontinent’ that existed between 500 and 180 million years ago. For the past four decades, geologists have debated how Gondwana eventually broke up, developing a multitude of scenarios which can be loosely grouped into two schools of thought – one theory claiming the continent separated into many small plates, and a second theory claiming it broke into just a few large pieces. Dr Eagles, working with Dr Matthais König from the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany, has devised a new computer model showing that the supercontinent cracked into two pieces, too heavy to hold itself together.
Gondwana comprised of most of the landmasses in today’s Southern Hemisphere, including Antarctica, South America, Africa, Madagascar, Australia-New Guinea, and New Zealand, as well as Arabia and the Indian subcontinent of the Northern Hemisphere. Between around 250 and 180 million years ago, it formed part of the single supercontinent ‘Pangea’.
Evidence suggests that Gondwana began to break up at around 183 million years ago. Analysing magnetic and gravity anomaly data from some of Gondwana’s first cracking points – fracture zones in the Mozambique Basin and the Riiser-Larsen Sea off Antarctica – Dr Eagles and Dr König reconstructed the paths that each part of Gondwana took as it broke apart. The computer model reveals that the supercontinent divided into just two large, eastern and western plates. Approximately 30 million years later, these two plates started to split to form the familiar continents of today’s Southern Hemisphere.
‘You could say that the process is ongoing as Africa is currently splitting in two along the East African Rift,’ says Dr Eagles. ‘The previously held view of Gondwana initially breaking up into many different pieces was unnecessarily complicated. It gave fuel to the theory that a plume of hot mantle, about 2,000 to 3,000 kilometres wide, began the splitting process. A straight forward split takes the spotlight off plumes as active agents in the supercontinent’s breakup, because the small number of plates involved resembles the pattern of plate tectonics in the rest of Earth’s history during which plumes have played bit parts.’
According to Dr Eagles and Dr König’s study, because supercontinents like Gondwana are gravitationally unstable to begin with, and have very thick crusts in comparison to oceans, they eventually start to collapse under their own weight.
Says Dr Eagles, ‘These findings are a starting point from which more accurate and careful research can be made on the supercontinent. The new model challenges the positions of India and Sri Lanka in Gondwana which have been widely used for the past 40 years, assigning them very different positions in the supercontinent. These differences have major consequences for our understanding of Earth.’
Adapted from materials provided by Royal Astronomical Society.

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Extreme Ocean Storms Have Become More Frequent Over Past Three Decades, Study Of Tiny Tremors Shows

Source:

http://www.sciencedaily.com/releases/2008/04/080417105456.htm

ScienceDaily (Apr. 21, 2008) — Data from faint earth tremors caused by wind-driven ocean waves -- often dismissed as "background noise" at seismographic stations around the world -- suggest extreme ocean storms have become more frequent over the past three decades. The International Panel on Climate Change (IPCC) and other prominent researchers have predicted that stronger and more frequent storms may occur as a result of global warming trends. The tiny tremors, or microseisms, offer a new way to discover whether these predictions are already coming true, said Richard Aster, a geophysics professor at the New Mexico Institute of Mining and Technology.

Unceasing as the ocean waves that trigger them, the microseisms show up as five- to 30-second oscillations of Earth's surface at seismographic stations around the world. Even seismic monitoring stations "in the middle of a continent are sensitive to the waves crashing all around the continent," Aster said.
As storm winds drive ocean waves higher, the microseism signals increase their amplitude as well, offering a unique way to track storm intensities across seasons, over time, and at different geographical locations. For instance, Aster and colleagues Daniel McNamara from the U.S. Geological Survey and Peter Bromirski of the Scripps Institution of Oceanography recently published analysis in the Seismological Society of America journal Seismological Research Letters showing that microseism data collected around the Pacific Basin and throughout the world could be used to detect and quantify wave activity from multi-year events such as the El Niño and La Niña ocean disruptions.
The findings spurred them to look for a microseism signal that would reveal whether extreme storms were becoming more common in a warming world. In fact, they saw "a remarkable thing," among the worldwide microseism data collected from 1972 to 2008, Aster recalled. In 22 of the 22 stations included in the study, the number of extreme storm events had increased over time, they found.
While the work on evaluating changes in extreme storms is "still very much in its early stages", Aster is "hoping that the study will offer a much more global look" at the effects of climate change on extreme storms and the wind-driven waves that they produce. At the moment, most of the evidence linking the two comes from studies of hurricane intensity and shoreline erosion in specific regions such as the Pacific Northwest Gulf of Mexico, he noted.
The researchers are also working on recovering and digitizing older microseism records, potentially creating a data set that stretches back to the 1930s. Aster praised the work of the long-term observatories that have collected the records, calling them a good example of the "Cinderella science"--unloved and overlooked--that often support significant discoveries.
"It's absolutely great data on the state of the planet. We took a prosaic time series, and found something very interesting in it," he said.
The presentation of "Microseism-Based Climate Monitoring" was made in the session: Models, Methods, and Measurements: Seismic Monitoring Research on April 17, 2008 at the annual meeting of the Seismological Society of America. Authors include Aster, R. New Mexico Institute of Mining and Technology; McNamara, D., U.S. Geological Survey in Golden, CO; Bromirski, P., Scripps Institution of Oceanography; and Gee, L., and Hutt, C.R., U.S. Geological Survey in Albuquerque, NM.
Adapted from materials provided by Seismological Society of America, via EurekAlert!, a service of AAAS.

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Greenland Ice May Not Be Headed Down Too Slippery A Slope, But Stability Still Far From Assured

Source:

http://www.sciencedaily.com/releases/2008/04/080417142507.htm

ScienceDaily (Apr. 20, 2008) — Lubricating meltwater that makes its way from the surface down to where a glacier meets bedrock turns out to be only a minor reason why Greenland's outlet glaciers accelerated their race to the sea 50 to 100 percent in the 1990s and early 2000s, according to University of Washington's Ian Joughin and Woods Hole Oceanographic Institution's Sarah Das. The two are lead co-authors of two papers posted April 18 on the Science Express website.

The report also shows that surface meltwater is reaching bedrock farther inland under the Greenland Ice Sheet, something scientists had speculated was happening but had little evidence.
"Considered together, the new findings indicate that while surface melt plays a substantial role in ice sheet dynamics, it may not produce large instabilities leading to sea level rise," says Joughin, a glaciologist with the UW's Applied Physics Laboratory. Joughin goes on to stress that "there are still other mechanisms that are contributing to the current ice loss and likely will increase this loss as climate warms."
Outlet glaciers are rapid flows of ice that start in the Greenland Ice Sheet and extend all the way to the ocean, where their fronts break apart in the water as icebergs, a process called calving. While most of the ice sheet moves less than one tenth a mile a year, some outlet glaciers gallop along at 7.5 miles a year, making outlet glaciers a concern because of their more immediate potential to cause sea level rise.
If surface meltwater lubrication at the intersection of ice and bedrock was playing a major role in speeding up the outlet glaciers, one could imagine how global warming, which would create ever more meltwater at the surface, could cause Greenland's ice to shrink much more rapidly than expected -- even catastrophically. Glacial ice is second only to the oceans as the largest reservoir of water on the planet and 10 percent of the Earth's glacial ice is found in Greenland.
It turns out, however, that when considered over an entire year, surface meltwater was responsible for only a few percent of the movement of the six outlet glaciers monitored, says Joughin, lead author of "Seasonal Speedup along the Western Flank of the Greenland Ice Sheet." Even in the summer it appears to contribute at most 15 percent, and often considerably less, to the total annual movement of these fast-moving outlet glaciers.
Calculations were made both by digitally comparing pairs of images acquired at different times from the Canadian RADARSAT satellite and by ground-based GPS measurements in a project funded by the National Science Foundation and National Aeronautics and Space Administration.
But while surface meltwater plays an inconsequential role in the movement of outlet glaciers, meltwater is responsible for 50 to 100 percent of the summer speed up for the large stretches near the edge of the ice sheet where there are no major outlet glaciers, a finding consistent with, but somewhat larger than, earlier observations.
"What Joughin, Das and their co-authors confirm is that iceflow speed up with meltwater is a widespread occurrence, not restricted to the one site where previously observed. But, they also show that the really fast-moving ice doesn't speed up very much with this. So we can expect the ice sheet in a warming world to shrink somewhat faster than previously expected, but this mechanism will not cause greatly faster shrinkage," says Richard Alley, professor of geosciences at Pennsylvania State University, who is not connected with the papers.
So what's behind the speed up of Greenland's outlet glaciers" Joughin says he thinks what's considerably more significant is when outlet glaciers lose large areas of ice at their seaward ends through increased calving, which may be affected by warmer temperatures. He's studied glaciers such as Jakobshavn Isbrae, one of Greenland's fastest-moving glaciers, and says that as ice calves and icebergs float away it is like removing a dam, allowing ice farther uphill to stream through to the ocean more quickly. At present, iceberg calving accounts for approximately 50 percent of the ice loss of Greenland, much of which is balanced by snowfall each winter. Several other studies recently have shown that the loss from calving is increasing, contributing at present rates to a rise in sea level of 1 to 2 inches per century.
"We don't yet know what warming temperatures means for increased calving of icebergs from the fronts of these outlet glaciers," Joughin says.
Until now scientists have only speculated if, and how, surface meltwater might make it to bedrock from high atop the Greenland Ice Sheet, which is a half-mile or more thick in places. The paper "Fracture Propagation to the Base of the Greenland Ice Sheet During Supraglacial Lake Drainage," with Woods Hole Oceanographic Institution's glaciologist Das as lead author, presents evidence of how a lake that disappeared from the surface of the inland ice sheet generated so much pressure and cracking that the water made it to bedrock in spite of more than half a mile of ice.
The glacial lake described in the paper was 2 to 2 ½ miles at its widest point and 40 feet deep. Researchers installed monitoring instruments and, 10 days after leaving the area, a large fracture developed, a crack spanning nearly the full length of the lake. The lake drained in 90 minutes with a fury comparable to that of Niagara Falls. (The researchers were ever so glad they hadn't been on the lake in their 10-foot boat with its 5-horsepower engine and don't plan future instrument deployments when the lakes are full of water. They'll get them in place only when the lakes are dry.)
Measurements after the event suggest there's an efficient drainage system under the ice sheet that dispersed the meltwater widely. The draining of multiple lakes each could explain the observed net regional summer ice speedup, the authors write.
Along with Das and Joughin other authors on the two papers are Matt King, Newcastle University, UK; Ben Smith, Ian Howat (now at Ohio State) and Twila Moon of the UW's Applied Physics Laboratory; Mark Behn and Dan Lizarralde of Woods Hole Oceanographic Institution; and Maya Bhatia, Massachusetts Institute of Technology/WHOI Joint Program.
Adapted from materials provided by University of Washington.

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Climate Change Likely To Intensify Storms, New Study Confirms

Source:

http://www.sciencedaily.com/releases/2008/04/080417170213.htm

ScienceDaily (Apr. 19, 2008) — Hurricanes in some areas, including the North Atlantic, are likely to become more intense as a result of global warming even though the number of such storms worldwide may decline, according to a new study by MIT researchers.

Kerry Emanuel, the lead author of the new study, wrote a paper in 2005 reporting an apparent link between a warming climate and an increase in hurricane intensity. That paper attracted worldwide attention because it was published in Nature just three weeks before Hurricane Katrina slammed into New Orleans.
Emanuel, a professor of atmospheric science in MIT's Department of Earth, Atmospheric and Planetary Sciences, says the new research provides an independent validation of the earlier results, using a completely different approach. The paper was co-authored by postdoctoral fellow Ragoth Sundararajan and graduate student John Williams and recently appeared in the Bulletin of the American Meteorological Society.
While the earlier study was based entirely on historical records of past hurricanes, showing nearly a doubling in the intensity of Atlantic storms over the last 30 years, the new work is purely theoretical. It made use of a new technique to add finer-scale detail to computer simulations called Global Circulation Models, which are the basis for most projections of future climate change.
"It strongly confirms, independently, the results in the Nature paper," Emanuel said. "This is a completely independent analysis and comes up with very consistent results."
Worldwide, both methods show an increase in the intensity and duration of tropical cyclones, the generic name for what are known as hurricanes in the North Atlantic. But the new work shows no clear change in the overall numbers of such storms when run on future climates predicted using global climate models.
However, Emanuel says, the new work also raises some questions that remain to be understood. When projected into the future, the model shows a continuing increase in power, "but a lot less than the factor of two that we've already seen" he says. "So we have a paradox that remains to be explained."
There are several possibilities, Emanuel says. "The last 25 years' increase may have little to do with global warming, or the models may have missed something about how nature responds to the increase in carbon dioxide."
Another possibility is that the recent hurricane increase is related to the fast pace of increase in temperature. The computer models in this study, he explains, show what happens after the atmosphere has stabilized at new, much higher CO2 concentrations. "That's very different from the process now, when it's rapidly changing," he says.
In the many different computer runs with different models and different conditions, "the fact is, the results are all over the place," Emanuel says. But that doesn't mean that one can't learn from them. And there is one conclusion that's clearly not consistent with these results, he said: "The idea that there is no connection between hurricanes and global warming, that's not supported," he says.
The work was partly funded by the National Science Foundation.
Adapted from materials provided by Massachusetts Institute Of Technology.

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Global Land Temperature Warmest On Record In March 2008

Source:

http://www.sciencedaily.com/releases/2008/04/080418112341.htm

ScienceDaily (Apr. 19, 2008) — The average global land temperature last month was the warmest on record and ocean surface temperatures were the 13th warmest. Combining the land and the ocean temperatures, the overall global temperature ranked the second warmest for the month of March. Global temperature averages have been recorded since 1880.

An analysis by NOAA’s National Climatic Data Center shows that the average temperature for March in the contiguous United States ranked near average for the past 113 years. It was the 63rd warmest March since record-keeping began in the United States in 1895.
Global Highlights
The global land surface temperature was the warmest on record for March, 3.3°F above the 20th century mean of 40.8°F. Temperatures more than 8°F above average covered much of the Asian continent. Two months after the greatest January snow cover extent on record on the Eurasian continent, the unusually warm temperatures led to rapid snow melt, and March snow cover extent on the Eurasian continent was the lowest on record.
The global surface (land and ocean surface) temperature was the second warmest on record for March in the 129-year record, 1.28°F above the 20th century mean of 54.9°F. The warmest March on record (1.33°F above average) occurred in 2002.
Although the ocean surface average was only the 13th warmest on record, as the cooling influence of La Niña in the tropical Pacific continued, much warmer than average conditions across large parts of Eurasia helped push the global average to a near record high for March.
Despite above average snowpack levels in the U.S., the total Northern Hemisphere snow cover extent was the fourth lowest on record for March, remaining consistent with boreal spring conditions of the past two decades, in which warming temperatures have contributed to anomalously low snow cover extent.
Some weakening of La Niña, the cold phase of the El Niño-Southern Oscillation, occurred in March, but moderate La Niña conditions remained across the tropical Pacific Ocean.
U.S. Temperature Highlights
In the contiguous United States, the average temperature for March was 42°F, which was 0.4°F below the 20th century mean, ranking it as the 63rd warmest March on record, based on preliminary data.
Only Rhode Island, New Mexico and Arizona were warmer than average, while near-average temperatures occurred in 39 other states. The monthly temperature for Alaska was the 17th warmest on record, with an average temperature 3.8°F above the 1971-2000 mean.
The broad area of near-average temperatures kept the nation’s overall temperature-related residential energy demand for March near average, based on NOAA’s Residential Energy Demand Temperature Index.
U.S. Precipitation Highlights
Snowpack conditions dropped in many parts of the West in March, but in general, heavy snowfall during December-February has left the western snow pack among the healthiest in more than a decade, with most locations near to above average.
Nine states from Oklahoma to Vermont were much wetter than average, with Missouri experiencing its second wettest March on record. Much of the month’s precipitation fell March 17-20, when an intense storm system moved slowly from the southern Plains through the southern Midwest.
Rainfall amounts in a 48-hour period totaled 13.84 inches in Cape Girardeau, Mo., and 12.32 inches in Jackson, Mo. The heavy rainfall combined with previously saturated ground resulted in widespread major flooding of rivers and streams from the Missouri Ozarks eastward into southern Indiana.
From March 7-9, eight to 12 inches of snow fell from Louisville, Ky., to central Ohio. In Columbus, an all-time greatest 24-hour snowfall of 15.5 inches broke the old record of 12.3 inches set on April 4, 1987.
In the Southeast, a powerful tornado moved through downtown Atlanta on March 14, causing significant damage to many buildings. This was one of 90 tornado reports from the Southeast in March.
Rainfall in the middle of March improved drought conditions in much of the Southeast, but moderate-to-extreme drought still remained in more than 59 percent of the region.
In the western U.S., the weather pattern in March bore a greater resemblance to a typical La Niña, with especially dry conditions across Utah, Arizona, Nevada, and California. March was extremely dry in much of California, tying as the driest in 68 years at the Sacramento airport with 0.05 inches, a 2.75 inch departure from average.
Adapted from materials provided by National Oceanic And Atmospheric Administration.

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Millions Of Pounds Of Trash Found On Ocean Beaches

Source:

http://www.sciencedaily.com/releases/2008/04/080416214912.htm

ScienceDaily (Apr. 18, 2008) — Ocean Conservancy released its annual report on trash in the ocean with new data from the 2007 International Coastal Cleanup the most comprehensive snapshot of the harmful impacts of marine debris. The mission of Ocean Conservancy’s International Coastal Cleanup is to engage people to remove trash from the world’s beaches and waterways, to identify the sources of debris and to change the behaviors that cause pollution.

This year, more than 378,000 volunteers participated in cleanups around every major body of water around the globe. Volunteers record the trash found on land and underwater allowing Ocean Conservancy a global snapshot of the problem.
"Our ocean is sick," says Laura Capps, Senior Vice President at Ocean Conservancy. "And the plain truth is that our ocean ecosystem cannot protect us unless it is healthy and resilient. Harmful impacts like trash in the ocean, pollution, climate change, and habitat destruction are taking its toll. But the good news is that hundreds of thousands of people from around the world are starting a sea change by joining together to clean up the ocean. Trash doesn’t’ fall from the sky it falls from people’s hands. With the International Coastal Cleanup, everyone has an opportunity to make a difference, not just on one day but all year long."
Trash in the ocean kills more than one million seabirds and 100,000 marine mammals and turtles each year through ingestion and entanglement. This year, 81 birds, 63 fish, 49 invertebrates, 30 mammals 11 reptiles and one amphibian were found entangled in debris by volunteers. Some of the debris they were entangled or had ingested include plastic bags, fishing line, fishing nets, six-pack holders, string from a balloon or kite, glass bottles and cans.
Entanglement in Ocean Trash
Wraps around flippers causing circulation loss and amputations
Creates wounds and cuts leading to bacterial infections
Slows animals ability to swim making them more vulnerable to predators
Smothers or traps animals, causing them to drown
Causes starvation as animals can no-longer eat or feed its young
Ingestion of Ocean Trash
Leads to starvation by blocking digestive tracks
Provides false sense of being full once swallowed, which leads to starvation
Ingests sharp objects like metal or glass that perforate the stomach, causing internal bleeding
Becomes lodged in animals windpipes, cutting off airflow and causing suffocation
How Long Does It Take for Trash in the Ocean to Decompose?
A tin can that entered the ocean in 1986 is still decomposing in 2036
A plastic bottle that entered the ocean in 1986 is decomposing in 2436
A glass bottle that entered the ocean in 1986 is decomposing in year 1,001,986
Prevention is the real solution to trash in the ocean. The International Coastal Cleanup volunteers make ocean conservation an everyday priority. Since 1986, more than six million volunteers have removed 116,000,000 pounds of debris across 211,460 miles of shoreline in 127 nations. The 23rd annual Flagship International Coastal Cleanup will be held Sept. 20, 2008.
Adapted from materials provided by Ocean Conservancy.

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