Climate News

The Arctic sea ice cover appears to have reached its minimum extent for the year, the third-lowest recorded since satellites began measuring sea ice extent in 1979, according to the University of Colorado at Boulder's National Snow and Ice Data Center.

While this year's September minimum extent was greater than 2007 and 2008, the two record-setting and near-record-setting low years, it is still significantly below the long-term average and well outside the range of natural climate variability, according to CU-Boulder's NSIDC scientists. Most researchers believe the shrinking Arctic sea ice is tied to warming temperatures caused by an increase in human-produced greenhouse gases being pumped into Earth's atmosphere.

On Sept. 10 the sea ice extent dropped to 1.84 million square miles, or 4.76 million square kilometers, and is likely the lowest ice extent of the year as sea ice appears to have begun its annual cycle of growth.

The 2010 minimum ice extent is 93,000 square miles, or 240,000 square kilometers, above the 2008 numbers and 240,000 square miles, or 630,000 square kilometers, above the record low in 2007. The 2010 sea ice extent is 130,000 square miles, or 340,000 square kilometers, below 2009, according to Serreze.
"We are still looking at summers with an ice-free Arctic Ocean in perhaps 20 to 30 years," said Serreze, also a professor in CU-Boulder's geography department.

The 2010 minimum is 753,000 square miles, or 1.95 million square kilometers, below the 1879-2000 average minimum and 625,000 square miles, or 1.62 million square kilometers, below the 1979 to 2010 average minimum.

Since NSIDC researchers determine the minimum sea ice extent using a five-day running average, there is still a small chance the sea ice extent could fall slightly, said Serreze. CU-Boulder's NSIDC will provide more detailed information in early October with a full analysis of the 2010 Arctic ice conditions, including aspects of the melt season and conditions heading into the winter ice-growth season.

NSIDC is part of CU-Boulder's Cooperative Institute for Research in Environmental Sciences -- a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration -- and is funded primarily by NASA.

For more information contact NSIDC's Jane Beitler at 303-492-1497 or Jim Scott in the CU-Boulder Office of News Services at 303-492-3114.

Contact
Jane Beitler, NSIDC, 303-492-1497
 (Jbeitler@nsidc.org
)

Jim Scott, CU News Services, 303-492-3114
 (Jim.Scott@colorado.edu)
 

The recently created Renewable and Sustainable Energy Institute (formerly
the CU-Boulder Energy Initiative), in partnership with corporate sponsors,
will be holding its Third Annual Research Symposium on Wednesday, October
21st at the University Memorial Center (UMC) on the CU-Boulder Campus.

The symposium will begin with a keynote address by Professor Steve Rayner of
the University of Oxford, followed by a poster session in which faculty,
research associates, graduate students and scientists display research
projects and ideas for tackling energy and related climate change or
sustainability issues.  More importantly, participants can learn about
related research interests and expertise on the CU campus and at local
federal laboratories (e.g. NREL, NOAA, NCAR, etc.). Poster presentations on
all aspects of renewable energy and energy sustainability are welcome.

A Seed Grant Competition with awards up to $50,000 will be held following
the Research Symposium.  Only poster participants in the Research Symposium
will be eligible to submit proposals to the Seed Grant Competition.
Specific proposal instructions and reviewing criteria, as well as an
application form, will be available immediately following the Symposium.

Registration for the Research Symposium is free and open to the public and
will be available on the RASEI site, http://rasei.colorado.edu/ , in the
next few weeks, along with additional details.
 

As the West warms, a drier Colorado River system could see as much as a one-in-two chance of fully depleting all of its reservoir storage by mid-century assuming current management practices continue on course, according to a new University of Colorado at Boulder study.

The study, in press in the American Geophysical Union journal, Water Resources Research, looked at the effects of a range of reductions in Colorado River stream flow on future reservoir levels and the implications of different management strategies. Roughly 30 million people depend on the Colorado River -- which hosts more than a dozen dams along its 1,450 journey from Colorado’s Rocky Mountains to the Gulf of California -- for drinking and irrigation water.

The Colorado River system is presently enduring its 10th year in a drought that began in 2000, said lead study author Balaji Rajagopalan, a CU-Boulder associate professor of civil, environmental and architectural engineering. Fortunately, the river system entered the drought with the reservoirs at approximately 95 percent of capacity. The reservoir system is presently at 59 percent of capacity, about the same as this time last year, said Rajagopalan, also a fellow at CU-Boulder’s Cooperative Institute for Research in Environmental Sciences.

The research team examined the future vulnerability of the system to water supply variability coupled with projected changes in water demand.  The team found that through 2026, the risk of fully depleting reservoir storage in any given year remains below 10 percent under any scenario of climate fluctuation or management alternative. During this period, the reservoir storage could even recover from its current low level, according to the researchers.

But if climate change results in a 10 percent reduction in the Colorado River’s average stream flow as some recent studies predict, the chances of fully depleting reservoir storage will exceed 25 percent by 2057, according to the study.  If climate change results in a 20 percent reduction, the chances of fully depleting reservoir storage will exceed 50 percent by 2057, Rajagopalan said.

“On average, drying caused by climate change would increase the risk of fully depleting reservoir storage by nearly ten times more than the risk we expect from population pressures alone,” said Rajagopalan.  “By mid-century this risk translates into a 50 percent chance in any given year of empty reservoirs, an enormous risk and huge water management challenge,” he said.

But even under the most extensive drying scenario, threats to water supplies won’t be felt immediately. “There’s a tremendous storage capacity on the Colorado River that helps with the reliability of supply over periods of a just few years,” said Rajagopalan.

Total storage capacity of reservoirs on the Colorado exceeds 60 million acre feet, almost 4 times the average annual flow on the river, and the two largest reservoirs -- Lake Mead and Lake Powell -- can store up to 50 million acre feet of water. As a result, the risk of full reservoir depletion will remain low through 2026, even with a 20 percent stream flow reduction induced by climate change, said Rajagopalan.

Between 2026 and 2057, the risks of fully depleting reservoir storage will increase seven-fold under the current management practices when compared with risks expected from population pressures alone. Implementing more aggressive management practices -- in which downstream releases are reduced during periods of reservoir shortages -- could lead to only a two-fold increase in risk of depleting all reservoir storage during this period, according to the study.

The magnitude of the risk will ultimately depend on the extent of climate drying and on the types of water management and conservation strategies established, according to the CU-Boulder study.

“Water conservation and relatively small pre-planned delivery shortages tied to declining reservoir levels can play a big part in reducing our risk,” said Ken Nowak, a graduate student with CU-Boulder’s Center for Advanced Decision Support for Water and Environmental Systems, or CADSWES, and a study co-author.

“But the more severe the drying with climate change, the more likely we will see shortages and perhaps empty reservoirs despite our best efforts.” Nowak said. “The important thing is not to get lulled into a sense of safety or security with the near-term resiliency of the Colorado River basin water supply. If we do, we’re in for a rude awakening.”

“This study, along with others that predict future flow reductions in the Colorado River Basin, suggests that water managers should begin to re-think current water management practices during the next few years before the more serious effects of climate change appear,” said Rajagopalan.

Titled “Water Supply Risk on the Colorado River: Can Management Mitigate?” the study was conducted with support from the Western Water Assessment – a joint venture of CU-Boulder and the National Oceanic and Atmospheric Administration, as well as CADSWES and the Bureau of Reclamation.

Other study authors included James Prairie of the Bureau of Reclamation, Martin Hoerling and Andrea Ray of NOAA, Joseph Barsugli and Bradley Udall of CIRES and Benjamin Harding of AMEC Earth & Environmental Inc. of Boulder.

Contact:
Balaji Rajagopalan, 303-492-5968
Rajagopalan.Balaji@Colorado.edu
Kenneth Nowak, 303-492-0892
Carol Rowe, 303-492-7426
Adriana Bailey, 303-492-6289

A small NASA aircraft completed its first successful science flight Thursday in partnership with the University of Colorado at Boulder as part of an expedition to study the receding Arctic sea ice and improve understanding of its life cycle and the long-term stability of the Arctic ice cover.  The mission continues through July 24.
 
NASA’s Characterization of Arctic Sea Ice Experiment, known as CASIE, began a series of unmanned aircraft system flights in coordination with satellites.  Working with CU-Boulder and its research partners, NASA is using the remotely piloted aircraft to image thick, old slabs of ice as they drift from the Arctic Ocean south through the Fram Strait -- which lies between Greenland and Svalbard, Norway -- and into the North Atlantic Ocean.
 
NASA’s Science Instrumentation Evaluation Remote Research Aircraft, or SIERRA, will weave a pattern over open ocean and sea ice to map and measure ice conditions below cloud cover to as low as 300 feet.
 
“Our project is attempting to answer some of the most basic questions regarding the most fundamental changes in sea-ice cover in recent years,” said CU-Boulder Research Professor James Maslanik of the aerospace engineering sciences department and principal investigator for the NASA mission.  “Our analysis of satellite data shows that in 2009 the amount of older ice is just 12 percent of what it was in 1988 -- a decline of 74 percent.  The oldest ice types now cover only 2 percent of the Arctic Ocean as compared to 20 percent in the 1980s.”
 
SIERRA, laden with scientific instruments, travels long distances at low altitudes, flying below the clouds. The aircraft has high maneuverability and slow flight speed.  SIERRA’s relatively large payload, approximately 100 pounds, combined with a significant range of 500 miles and a small, 20-foot wingspan, makes it the ideal aircraft for the expedition.
 
The mission is conducted from the Ny-Alesund research base on the island of Svalbard, Norway, located near the northeastern tip of Greenland.  Mission planners are using satellite data to direct flights of the aircraft.
 
“We demonstrated the utility of small- to medium-class unmanned aircraft systems for gathering science data in remote, harsh environments during the CASIE mission,” said Matt Fladeland, CASIE project and SIERRA manager at NASA’s Ames Research Center in Moffett Field, Calif.
 
The aircraft observations will be complemented by NASA satellite large-scale views of many different features of the Arctic ice.  The Moderate Resolution Imaging Spectroradiometer aboard NASA’s Aqua satellite will be used to identify the ice edge location, ice features of interest and cloud cover. Other sensors such as the Advanced Microwave Scanning Radiometer-Earth Observing System on Aqua and the Quick Scatterometer satellite can penetrate cloud cover and analyze the physical properties of ice.
 
By using multiple types of satellite data, in conjunction with high-resolution aircraft products, more can be learned about ice conditions than is possible by using one or two data analysis methods.
 
NASA’s CASIE mission supports a larger NASA-funded research effort titled “Sea Ice Roughness as an Indicator of Fundamental Changes in the Arctic Ice Cover: Observations, Monitoring, and Relationships to Environmental Factors.”  The project also supports the goals of the International Polar Year, a major international scientific research effort involving many NASA research efforts to study large-scale environmental changes in Earth’s polar regions.
 
Other CU-Boulder participants in CASIE include Research Associate Ute Herzfeld, aerospace engineering graduate student Ian Crocker and Professional Research Assistant Katja Wegrzyn.
 
The CASIE expedition is providing mission updates online at:
 
http://blogs.nasa.gov/cm/blog/CASIE
 
http://twitter.com/NASA_CASIE
 
For more information about CASIE visit http://www.espo.nasa.gov/casie/.

Contact:

James Maslanik, 303-492-8974

James.Maslanik@colorado.edu

Jim.Scott@colorado.edu

According to Colorado lore, a settler named Mike Callahan came to the state's Western Slope in 1882 and settled along Parachute Creek. He built a log cabin from the sturdy pines of the area and finished it off with a fireplace and chimney made from the abundant rocks he found on nearby hills. But when he lit a fire in the hearth his housewarming suddenly took on new meaning when the chimney rocks burst into flames, engulfing the entire house.

Callahan discovered too late that the Piceance Basin is full of flammable rock called oil shale, and in the decades to follow it would become the center of a major debate among landowners, oil companies, environmentalists and the government.

The University of Colorado at Boulder's Center of the American West has put together an online report titled "What Every Westerner Should Know About Oil Shale" to help bring an impartial perspective to the debate over oil shale. After two previous booms and busts, including a regionally devastating downturn in the early 1980s, it looks like another oil shale development cycle is on the horizon. It's a prospect local residents, policymakers and concerned citizens throughout the country regard with a mix of anticipation and apprehension.

The report was authored by history Professor Patty Limerick, faculty director and chair of the Center of the American West's board, and Jason Hanson, a member of the center's research staff since 2004.

Hanson said the intent of the report is "to provide a safe port in the storm of data disputes that usually rage on topics like this. We want to encourage a more responsible, more informed and more productive decision-making process."

Said Limerick, "As a historian, I've read as much as I care to read and studied as much as I care to study about people acting in haste. I really don't need more of that. So it was great for me to look at a situation where there is such a process of deliberation going on."

Two years in the making, the online report details the first two oil shale booms on the western slope of the Rocky Mountains -- where the world's largest supplies of the substance lie trapped beneath the surface -- and the reasons those efforts ultimately failed.

Looking ahead to the new round of oil shale development, Limerick and Hanson survey efforts currently under way in Colorado and Utah. The report examines ways in which energy companies and other stakeholders can anticipate and manage the variety of social, economic and environmental issues raised by the prospect of creating an oil shale industry in the mountain West.

The report does not suggest that past failures necessarily predict the future for oil shale. Limerick is quick to point out that almost every human enterprise is met with adversity at first and that the day could come when oil extracted from shale is flowing out of the West by the barrel.

"There are unknowns and uncertainties," Limerick said. "There is certainly no guarantee that this will work. But its failure is not predictable, either. History offers a remarkable record of human ingenuity powering past obstacles."

Judicious estimates suggest that 800 billion barrels -- more than triple Saudi Arabia's proven reserves and enough to meet current U.S. demand for more than a century -- might one day be extracted from the Green River Formation along the T-shaped border of Colorado, Wyoming and Utah. The richest known deposits are located in Colorado's Piceance Basin, an area of more than 1,300 square miles just north of Grand Junction.

One of the major environmental concerns related to U.S. oil shale development is water. Current research estimates that commercial production could require about three barrels of water for every barrel of oil, an amount many people say would be devastating in the arid West where many different interests already compete for every gallon.

Hanson said the Center of the American West takes no position either for or against oil shale production. The report grew out of a workshop funded by Chevron and people involved in its preparation on different sides of the debate have praised it.

"It's a very well balanced, very well done, comprehensive report and it has a particularly excellent historical review of oil shale in terms of the efforts that have been done in the past and kind of drawing attention to the issues that oil shale development brings to a region," said Tracy Boyd, communications and sustainability manager for Shell Exploration and Production Company on Unconventional Oil.

Karin Sheldon, executive director of Western Resource Advocates, a nonprofit environmental law and policy organization headquartered in Boulder, agreed.

"I think the center's report is terrific," Sheldon said. "It gives a good overview of the issues involved in oil shale development. It's an important document for public education and to help inform the debate that we all need to have about oil shale."

Limerick is glad to see all sides on the question of oil shale development talking about the issues involved.

"It's spirit-lifting to see a society thinking, 'No, we need to really think before we move ahead on this,' " said Limerick. "At long last, we have gotten to a stage of trying to think as hard as we can about our actions and their likely consequences. This seems like a really great act of maturation as a group of human beings."

The online report will be updated to stay current with recent developments. It also will feature space for comments and discussion from stakeholders who have an interest in oil shale development.

See the CU-Boulder Center of the American West's report "What Every Westerner Should Know About Oil Shale" at http://oilshale.centerwest.org.

A CU-Boulder video news release on the topic can be accessed at http://www.colorado.edu/news by clicking on the headline about the oil shale report.

Contact:
Jason Hanson, 303-492-4879
Jason.hanson@colorado.edu

Patty Limerick, 303-492-4879
Patricia.Limerick@colorado.edu

Peter Caughey, 303-492-4007

The Natural Resources Law Center (NRLC) and partners have developed a comprehensive, free-access, searchable, web-based database of best management practices (BMPs) for the Intermountain West.

The intention of this project of compiling BMPs is to protect all of the surface resources affected by oil and gas development - air and water quality, soils, vegetation, visual aesthetics, tranquility, health and safety, wildlife and other resources.  The database now includes more than 4000 records of BMPs currently in use, required and/or recommended in Colorado, Montana, New Mexico, Utah and Wyoming.

To access the website, visit http://www.oilandgasbmps.org

While a total or partial collapse of the West Antarctic Ice Sheet as a result of warming would not raise global sea levels as high as some predict, levels on the U.S. seaboards would rise 25 percent more than the global average and threaten cities like New York, Washington, D.C., and San Francisco, according to a new study.

Long thought of as the sleeping giant with respect to sea level rise, Antarctica holds about nine times the volume of ice of Greenland. Its western ice sheet, known as WAIS, is of particular interest to scientists due to its inherent instability, a result of large areas of the continent's bedrock lying below sea level. But the ice sheet's potential contribution to sea level rise has been greatly overestimated, according to new calculations.

"There's a vast body of research that's looked at the likelihood of a WAIS collapse and what implications such a catastrophic event would have for the globe," said Jonathan Bamber, lead author of the study published in Science May 15. "But all of these studies have assumed a 5-meter to 6-meter contribution to sea level rise. Our calculations show those estimates are much too large, even on a thousand-year timescale."

Bamber and his colleagues found a WAIS collapse would only raise sea levels by 3.3 meters, or about 11 feet. Bamber, a professor at the University of Bristol in England, currently is a visiting fellow at the University of Colorado at Boulder's Cooperative Institute for Research in Environmental Sciences, or CIRES.

The study authors used models based on glaciological theory to simulate how the massive ice sheet likely would respond if the floating ice shelves fringing the continent broke free. Vast ice shelves currently block WAIS from spilling into the Weddell and Ross seas, limiting total ice loss to the ocean.

According to theory, if these floating ice shelves were removed, sizeable areas of WAIS would essentially become undammed, triggering an acceleration of the ice sheet toward the ocean and a rapid inland migration of the grounding line.  The grounding line is the point where the ice sheet's margins meet the ocean and begin to float.

The most unstable areas of WAIS are those sections sitting in enormous inland basins on bedrock entirely below sea level. If the ice filling these basins becomes undammed by the disappearance of floating ice shelves, it quickly would become buoyant and form new floating ice shelves further inland, in time precipitating further breakup and collapse, according to existing theories.

The study authors assumed that only ice on the downward-sloping and inland-facing sides of the basins would be vulnerable to collapse.  They also assumed that ice grounded on inland bedrock that slopes upward or on bedrock that lies above sea level likely would survive.

"Unlike the world's other major ice sheets -- the East Antarctic Ice Sheet and Greenland -- WAIS is the only one with such an unstable configuration," said Bamber.

Just how rapid the collapse of WAIS would be is largely unknown. If such a large mass of ice steadily melted over 500 years, as has been suggested in earlier studies, it would add about 6.5 millimeters or a quarter of an inch per year to sea level rise -- about twice the current rate due to all sources.

"Interestingly, the pattern of sea level rise is independent of how fast or how much of the WAIS collapses," he said. "Even if the WAIS contributed only a meter of sea level rise over many years, sea levels along North America's shorelines would still increase 25 percent more than the global average," said Bamber.

Regional variations in sea level would largely be driven by the distribution of ice mass from the Antarctic continent to the oceans, according to the study. With less mass at the South Pole, Earth's gravity field would weaken in the Southern Hemisphere and strengthen in the Northern Hemisphere, causing water to pile up in the northern oceans.

This redistribution of mass also would affect Earth's rotation, which in turn would cause water to build up along the North American continent and in the Indian Ocean.

Study co-authors included Riccardo Riva and Bert Vermeersen from Delft University of Technology in the Netherlands and Anne LeBroq of the University of Durham in England.  The study was conducted with support from the Natural Environment Research Council.

Contact:
Jonathan Bamber, 303-492-8695
j.bamber@bristol.ac.uk

Adriana Bailey, 303-492-6289
Adriana.bailey@colorado.edu

An analysis of ancient Greenland ice suggests a spike in the greenhouse gas methane about 11,600 years ago originated from wetlands rather than the ocean floor or from permafrost, a finding that is good news according to the University of Colorado at Boulder scientist who led the study.

Methane bound up in ocean sediments and permafrost, called methane clathrate, has been a concern to scientists because of its huge volume, greenhouse gas potency and potential for release during periods of warming, said Vasilii Petrenko, a CU-Boulder postdoctoral fellow and lead study author. If just 10 percent of methane from clathrates -- an ice-like substance composed of methane and water -- were suddenly released into Earth's atmosphere, the resulting increase in the greenhouse effect would be equivalent to a 10-fold increase in atmospheric carbon dioxide, he said.

Using carbon 14 as a "tracer" to date and distinguish wetland methane from methane clathrates, an international team determined the methane jump 11,600 years ago likely emanated primarily from Earth's wetlands. "From a global warming standpoint, this appears to be good news," said Petrenko of CU-Boulder's Institute of Arctic and Alpine Research, lead author on a paper that was published in Science on April 24.

Methane is the third most powerful greenhouse gas behind water vapor and C02 and accounts for roughly 20 percent of the human-caused increase in the greenhouse effect.

As Earth emerged from the last ice age, temperatures in some places in the Northern Hemisphere shot up about 18 degrees Fahrenheit in just 20 years, said Petrenko.  Scientists have been concerned that such abrupt warming events could trigger huge oceanic methane "burps" caused by the dissociation of seafloor clathrates, providing a positive climate feedback mechanism that could drive up Earth's temperatures still further.

"If we found that clathrates release a lot of methane to the atmosphere during abrupt episodes of warming, that could signal big trouble for the planet, " said Petrenko. "But even though wetlands appear be the primary source, it's still something to be concerned about."

Methane emitted from human activities like rice cultivation, livestock, the burning of grasslands, forests and wood fuels, gas leaks from fossil fuel production and waste management activities have nearly tripled methane concentrations in Earth's atmosphere in the past 250 years, Petrenko said.  The amount of carbon held in methane clathrate deposits on Earth may equal the amount of carbon in all oil, coal and gas reserves on the planet, he said.

Study co-authors were from the Scripps Institution of Oceanography, Oregon State University, the Australian Nuclear Science and Technology Organisation, the National Institute of Water and Atmospheric Research in New Zealand, Danish Technical University and the Commonwealth Scientific and Industrial Research Organisation in Australia.  Petrenko conducted most of the research as part of his doctoral thesis at the Scripps Institution of Oceanography under Professor Jeffrey Severinghaus.

The research team extracted several tons of ancient ice from the western margin of the Greenland ice sheet at a site called Pakitsoq, the largest ice samples ever recovered for a climate change study.  The researchers cut the ice into blocks with electric chain saws, dumped 17 cubic feet at a time into a vacuum melting tank heated by powerful propane torches, and transferred ancient air released from bubbles in the ice into cylinders for subsequent laboratory analysis, Petrenko said.

The effort, which lasted five field-seasons, was "an undertaking of epic proportions," said Petrenko.  "This was the first measurement of its kind, and we really pushed the envelope," he said.  "It represents a major advance in analytical methods for studying ancient ice."

Methane clathrates are only stable in conditions that combine cold temperatures and high pressures. Some scientists suspect that a swift and massive warming in the early Cenozoic era about 56 million years ago may have been triggered by huge methane releases from clathrates into the atmosphere, Petrenko said.

Methane levels in Earth's atmosphere increased about 2 percent from about A.D. 1 to 1000 and decreased by 2 percent from 1000 to 1700, which may have been due in part to decreased landscape burning by indigenous people in the Americas devastated by introduced diseases, according to a 2005 CU-Boulder study. About 60 percent of atmospheric methane is now generated from human-related activities, according to the International Panel on Climate Change.

The 2009 Greenland ice study was funded by the National Science Foundation, the American Chemical Society and several other agencies. Petrenko's postdoctoral fellowship at CU-Boulder is funded by The University Corporation for Atmospheric Research.

Contact:
Vasilii Petrenko, 303-492-7132
Vasilii.petrenko@colorado.edu

Jim Scott, 303-492-3114

The latest data from NASA and the University of Colorado at Boulder's National Snow and Ice Data Center show the continuation of a decade-long trend of shrinking sea ice extent in the Arctic, including new evidence for thinning ice as well.

The researchers, who have been tracking Arctic sea ice cover with satellites since 1979, found that the winter of 2008-09 was the fifth lowest maximum ice extent on record. The six lowest maximum events in the satellite record have all occurred in the past six years, according to CU-Boulder researcher Walt Meier of NSIDC.

The new measurements by CU-Boulder's NSIDC show the maximum sea ice extent for 2008-09 reached on Feb. 28 was 5.85 million square miles, which is 278,000 square miles below the average extent for 1979 to 2000, an area slightly larger than the state of Texas, said Meier.

In addition, a team of CU-Boulder researchers led by Research Associate Charles Fowler of the Colorado Center for Astrodynamics Research, or CCAR, has found that younger, thinner ice has replaced older, thicker ice as the dominant type over the past five years, making it more prone to summer melt.

"Ice extent is an important measure of the health of the Arctic, but it only gives us a two dimensional view of the ice cover," said Meier. "Thickness is important, especially in the winter, because it is the best overall indicator of the health of the ice cover.  As the ice cover in the Arctic grows thinner, it becomes more vulnerable to summer melt."

Until recent years, measurements have shown most Arctic ice has survived at least one summer and often several, said Meier.  But the balance has now flipped, and seasonal ice -- which melts and re-freezes every year -- now comprises about 70 percent of Arctic sea ice in winter, up from 40 to 50 percent in the 1980s and 1990s, he said.  Thicker ice that has survived two or more years now comprises just 10 percent of ice cover, down from 30 to 40 percent in years past.

Scientists believe Arctic sea ice functions like an air conditioner for the global climate system by naturally cooling air and water masses, playing a key role in ocean circulation and reflecting solar radiation back into space.

In a related study led by Ron Kwok of NASA's Jet Propulsion Laboratory in Pasadena, Calif., researchers have demonstrated a way to estimate ice thickness over the entire Arctic Ocean. Using two years of data from NASA's Ice, Cloud and Land Elevation Satellite, or ICESat, the team made the first basin-wide estimate of the thickness and volume of the Arctic Ocean ice cover for 2005 and 2006.

"With the new data on the area and thickness of Arctic sea ice, we can now better understand the sensitivity and vulnerability of the ice cover to changes in climate," Kwok said.

A recent study by a team from CU-Boulder's CCAR concluded there has been a near complete loss of the oldest, thickest Arctic ice, and that 58 percent of perennial ice was only two to three years old.  In the mid-1980s, only 35 percent of that sea ice was that young and that thin, according to aerospace engineering sciences department Research Professor James Maslanik, who led the 2008 study published in Geophysical Research Letters.

"Heading into the 2009 summer melt season, the potential continues for extensive ice retreat due to the trend toward younger, thinner ice that has accelerated in recent years," said Maslanik, also a member of the Cooperative Institute for Research in Environmental Sciences.  "A key question will be whether this second year ice is thick enough to survive summer melt," said Maslanik.

"If it does, this might start a trend toward recovery of the perennial sea ice pack," Maslanik said. "If it doesn't, then this would be further evidence of the difficulty of re-establishing the ice conditions that were typical of 20 or 30 years ago."

The Arctic ice cap grows each winter as the sun sets for several months and intense cold sets in. The total volume of winter Arctic ice is equal to the volume of fresh water in Lake Superior and Lake Michigan combined.

While some sea ice is naturally pushed out of the Arctic by winds, much of it melts in place. First-year sea ice usually reaches 6 feet in thickness, while ice that has lasted through more than one summer averages 9 feet and can grow much thicker in some locations near the coast.

For more information visit http://nsidc.org/arcticseaicenews.

Contact:
Jane Beitler, 303-492-1497
jbeitler@nsidc.org

Walt Meier, 303-492-6508
walt@nsidc.org

James Maslanik, 303-492-8974
james.maslanik@colorado.edu

Jim Scott, 303-492-3114