climate change > newsfile > arctic forecast to lose ice cover within 100 years
Arctic forecast to lose ice cover within 100 YearsPosted: 04 Sep 2005
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 US 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.
Dramatic melting
"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."
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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)
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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.
The report is the result of week-long meeting of a team of interdisciplinary scientists, both government and academic, who examined how the Arctic environment and climate interact and how that system would respond as global temperatures rise.
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.
"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."
Feedback loops
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."
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Polar bears are losing their icy habitat in the Arctic and some scientists predict they will become extinct.
(Photo courtesy Greenpeace UK)
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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.
While the scientists identified one feedback loop that could slow the changes, 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. 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."
Copyright Environment News Service (ENS) 2005. All Rights Reserved.
Related links:
Jonathan Overpeck on-line
The University of Arizona's Institute for the Study of Planet Earth
The NSF Arctic System Science Program
Arctic lakes vanishing as planet warms
From our website:
People & the Planet website has published numerous features and news reports on the Arctic and climate which you can find on its Climate Change site.
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