World's Largest Aerosol Sensing Network Has Leafy Origins

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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

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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

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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

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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

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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

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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

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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.