Arctic Ocean Could Be Ice-Free in Summer Within 100 Years, Scientists Say

WASHINGTON - The current warming trends in the Arctic may shove the Arctic system into a seasonally ice-free state not seen for more than one million years, according to a new report. The melting is accelerating, and a team of researchers was unable to identify any natural processes that might slow the de-icing of the Arctic.

Such substantial additional melting of Arctic glaciers and ice sheets will raise sea level worldwide, flooding the coastal areas where many of the world's people live. Melting sea ice has already resulted in dramatic impacts for the indigenous people and animals in the Arctic, which includes parts of Alaska, Canada, Russia, Scandinavia, and Greenland.

The report is the result of week-long meeting of an interdisciplinary team of scientists that examined how the Arctic environment and climate interact and how that system would respond as global temperatures rise. It was organized by the National Science Foundation's Arctic System Science Committee, which is chaired by Jonathan T. Overpeck of the University of Arizona. The report by Overpeck, who also chaired the meeting, and 20 colleagues from the United States and Canada is published 23 August in Eos, the weekly newspaper of the American Geophysical Union.

"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 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 past climates in the Arctic include 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, such as the past 10,000 years. By studying natural data loggers such as 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.

At the workshop, the team of scientists synthesized what is currently known about the Arctic and defined key components that make up the current system. They identified how the components interact, including feedback loops that involve multiple parts of the system. "In the past, researchers have tended to look at individual components of the Arctic," said Overpeck. "What we did for the first time is really look at how all of those components work together."

The team concluded that there were two major amplifying feedbacks in the Arctic system, involving the interplay between sea and land ice, ocean circulation in the North Atlantic, and the amounts of precipitation and evaporation in the system. Such feedback loops accelerate changes in the system, Overpeck explained. For example, the white surface of sea ice reflects radiation from the Sun. As sea ice melts, more solar radiation is absorbed by the dark ocean, which heats up and results in yet more sea ice melting.

The scientists identified one feedback loop that could slow the changes, but they did not see any natural mechanism that could stop the dramatic loss of ice. "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, adding that the group investigated several possible braking mechanisms that had been previously suggested.

In addition to sea and land ice melting, Overpeck warned that permafrost, the permanently frozen layer of soil that underlies much of the Arctic landmass, 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.

Journalists (only) may obtain a pdf copy of this paper upon request to Jonathan Lifland: jlifland@agu.org. Please provide your name, name of publication, phone, and email address. The paper and this press release are not under embargo.

Title: "Arctic System on Trajectory to New, Seasonally Ice-Free State"

Authors:
Jonathan T. Overpeck, Institute for the Study of Planet Earth, University of Arizona, Tucson, Arizona, USA;
Matthew Sturm, Cold Regions Research and Engineering Laboratory, Fort Wainwright, Alaska, USA;
Jennifer A. Francis, Rutgers University, New Brunswick, New Jersey, USA;
Donald K. Perovich, the Cold Regions Research and Engineering Laboratory, Hanover, New Hampshire, USA;
Mark C. Serreze, University of Colorado, Boulder, Colorado, USA;
Ronald Benner, University of South Carolina, Columbia, South Carolina, USA;
Eddy C. Carmack, Institute of Ocean Sciences, Sidney, British Columbia, Canada;
F. Stuart Chapin III, University of Alaska, Fairbanks, Alaska, USA;
S. Craig Gerlach, University of Alaska, Fairbanks, Alaska, USA;
Lawrence C. Hamilton, University of New Hampshire, Durham, New Hampshire, USA;
Larry D. Hinzman of the University of Alaska, Fairbanks, Alaska, USA;
Marika Holland, National Center for Atmospheric Research, Boulder, Colorado, USA;
Henry P. Huntington, Huntington Consulting, Eagle River, Alaska USA;
Jeffrey R. Key, National Environmental Satellite, Data, and Information Service, National Oceanic and Atmospheric Administration, Madison, Wisconsin, USA;
Andrea H. Lloyd, Middlebury College, Middlebury, Virginia, USA;
Glen M. MacDonald, University of California, Los Angeles, California, USA;
Joe McFadden, University of Minnesota, St. Paul, Minnesota, USA;
David Noone, California Institute of Technology, Pasadena, California, USA;
Terry D. Prowse, University of Victoria, Victoria, British Columbia, Canada;
Peter Schlosser, Lamont-Doherty Earth Observatory, Columbia University, Palisades, New York, USA;
Charles Vörösmarty, University of New Hampshire, Durham New Hampshire, USA.

Citation:
Overpeck, J. T., M. Sturm, J. A. Francis, D. K. Perovich, M. C. Serreze, R. Benner, E. C. Carmack, F. S. Chapin III, S. C. Gerlach, L. C. Hamilton, L. D. Hinzman, M. Holland, H. P. Huntington, J. R. Key, A. H. Lloyd, G. M. MacDonald, J. McFadden, D. Noone, T. D. Prowse, P. Schlosser, and C. Vörösmarty, (2005), Arctic System on Trajectory to New, Seasonally Ice-Free State, Eos, Trans. AGU, 86(34), 309, 312-313.

Note: Author list may be shorted to Overpeck, J.T., et al.

Contact information for authors:
Jonathan T. Overpeck: jto@u.arizona.edu or +1 231-889-3566 or +1 520-907- 6480 (23-30 August); +1 970-728-0780 or +1 520-907-6480 (1 September and after)

Matthew Sturm: msturm@crrel.usace.army.mil or +1 907-353-5183 or +1 907-457-1898

Jennifer Francis: francis@imcs.rutgers.edu or +1732-708-1217

Mark C. Serreze: serreze@kryos.colorado.edu or +1 303-492-2963

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