Arctic Forecast to Lose Ice Cover Within 100 Years

TUCSON, Arizona, August 25, 2005 (ENS) - Climate warming across the Arctic is pushing the Arctic system into a seasonally ice-free state for the first time in more than one million years, concludes a new report by U.S. and Canadian scientists. The melting is accelerating, and the researchers could find no natural processes that might slow or reverse the thawing of Arctic glaciers and ice sheets.

The de-icing of the Arctic will raise sea levels worldwide, flooding coastal areas inhabited by millions of people, the scientists warn. The indigenous people and animals of the Arctic, which includes parts of Alaska, Canada, Russia, Siberia, Scandinavia and Greenland, are already feeling the heat.

"What really makes the Arctic different from the rest of the non-polar world is the permanent ice in the ground, in the ocean and on land," said lead author University of Arizona geoscientist Jonathan Overpeck. "We see all of that ice melting already, and we envision that it will melt back much more dramatically in the future as we move towards this more permanent ice-free state."

The report by Professor Overpeck and his colleagues is published in the August 23 issue of "Eos," the weekly newspaper of the American Geophysical Union.

Professor Jonathan Overpeck specializes in paleoclimatology, paleoecology, climate dynamics, and environmental decision-support. He is director of The Institute for the Study of Planet Earth,and heads the UA Department of Geosciences Environmental Studies Laboratory. (Photo courtesy University of Arizona (UA))

The workshop was organized by the National Science Foundation Arctic System Science Committee, which is chaired by Overpeck, director of the Institute for the Study of Planet Earth at the University of Arizona in Tucson. The National Science Foundation funded the meeting.

In the past, the Arctic has experienced glacial periods, where sea ice coverage expanded and ice sheets extended into Northern America and Europe, and warmer interglacial periods during which the ice retreats, as it has during the past 10,000 years.

By studying ice cores and marine sediments, scientists have a good idea what the "natural envelope" for Arctic climate variations has been for the past million years, Overpeck said.

Webcam image of instruments at the North Pole that measure melting ice. July 15, 2005. (Photo courtesy NOAA/Pacific Marine Environmental Laboratory)

The Arctic is "highly complex, with a tightly coupled system of people, land, ocean, ice and air that behaves in ways that we do not fully comprehend, and which has demonstrated a capacity for rapid and unpredictable change with global ramifications," the NSF Arctic System Science Program declares on its website. "The Arctic is pivotal to the dynamics of our planet and it is critical that we better understand this complex and interactive system."

Overpeck's team concluded that there are two major amplifying feedback systems in the Arctic that accelerate changes in the system. They involve the interplay between sea and land ice, ocean circulation in the North Atlantic, and the amounts of precipitation and evaporation in the system.

The white surface of sea ice reflects radiation from the sun, for example, Overpeck said. However, as sea ice melts, more solar radiation is absorbed by the dark ocean, which heats up and results in yet more sea ice melting.

Polar bears are losing their icy habitat and some scientists predict they will vanish into extinction. (Photo courtesy Greenpeace UK)

"I think probably the biggest surprise of the meeting was that no one could envision any interaction between the components that would act naturally to stop the trajectory to the new system," Overpeck said. While the group investigated several possible braking mechanisms that had been previously suggested, none appeared to be effective, he said.

In addition to sea and land ice melting, Overpeck warned that permafrost - the permanently frozen layer of soil that underlies much of the Arctic - will melt and eventually disappear in some areas. Such thawing could release additional greenhouse gases stored in the permafrost for thousands of years, which would amplify human-induced climate change.

Overpeck said humans could step on the brakes by reducing carbon dioxide emissions. "The trouble is we don't really know where the threshold is beyond which these changes are inevitable and dangerous," Overpeck said. "Therefore it is really important that we try hard, and as soon as we can, to dramatically reduce such emissions."

Overpeck's coauthors on the "Eos" paper are:

• Matthew Sturm of the Cold Regions Research and Engineering Laboratory in Fort Wainwright, Alaska
• Jennifer Francis of Rutgers University in New Brunswick, New Jersey
• Donald Perovich of the Cold Regions Research and Engineering Laboratory in Hanover, New Hampshire
• Mark Serreze of the University of Colorado, Boulder
• Ronald Benner of the University of South Carolina in Columbia
• Eddy Carmack of the Institute of Ocean Sciences in Sidney, British Columbia, Canada
• F. Stuart Chapin III of the University of Alaska, Fairbanks
• S. Craig Gerlach of the University of Alaska, Fairbanks
• Lawrence Hamilton of the University of New Hampshire in Durham
• Larry Hinzman of the University of Alaska, Fairbanks
• Marika Holland of the National Center for Atmospheric Research in Boulder, Colorado
• Henry Huntington of Huntington Consulting in Eagle River, Alaska
• Jeffrey Key of the National Oceanic and Atmospheric Administration's National Environmental Satellite, Data, and Information Service in Madison, Wisconsin
• Andrea Lloyd of Middlebury College in Middlebury, Virginia
• Glen M. MacDonald of the University of California, Los Angeles
• Joe McFadden of the University of Minnesota in St. Paul
• David Noone of the California Institute of Technology in Pasadena
• Terry Prowse of the University of Victoria, in British Columbia, Canada
• Peter Schlosser of Columbia University in Palisades, New York
• Charles Vörösmarty of the University of New Hampshire in Durham.

The University of Arizona's Institute for the Study of Planet Earth is found at: http://www.ispe.arizona.edu/

The NSF Arctic System Science Program: http://www.arcus.org/ARCSS/