Deborah Zabarenko, Reuters 10 Jun 08;
WASHINGTON (Reuters) - If Arctic sea ice starts melting fast, polar bears and ring seals wouldn't be the only creatures to feel it: A study released on Tuesday suggests it could spur warmer temperatures hundreds of miles (km) inland.
That means a possible thaw in the long-frozen soil known as permafrost, which in turn could have severe effects on ecosystems, human infrastructure like oil rigs and pipelines and the release of more global warming greenhouse gases in Russia, Alaska and Canada, the scientists said.
The study is particularly pertinent because of last year's record melt of Arctic sea ice, when ice cover in the Arctic Sea shrank to 30 percent below average. Another record melt is forecast for this year but it is unknown whether this is the beginning of a trend.
"Our climate model suggests that rapid ice loss is not necessarily a surprise," said David Lawrence of the National Center for Atmospheric Research, an author of the study.
"When you get certain conditions in the Arctic -- thin ice, a lot of first-year ice (as opposed to older, sturdier ice) -- that you can get a situation where ... you get a rapid and steady loss over a period of five to 10 years," Lawrence said by telephone from Colorado.
In such a period of rapid ice loss, autumn temperatures along the Arctic coasts of Russia, Alaska and Canada could rise by as much as 9 degrees F (5 degrees C), the study's climate model found. Autumn is often the warmest season in this area.
INTERCONNECTED ARCTIC
Last year's temperatures from August to October over land in the western Arctic were also unusually warm, more than 4 degrees F (about 2 degrees C) above the average temperatures for 1978-2006, raising questions about the relationship between shrinking sea ice and warmer land temperatures.
The scientists found that when sea ice melts rapidly, Arctic land warms three and a half times faster than the rate predicted in 21st century climate models. The warming is largest over the ocean but simulations indicate that it can extend as far as 900 miles inland.
In places where permafrost is already at risk, such as central Alaska, a quick sea ice melt could lead to a quick permafrost thaw.
The effects of melting are already evident in parts of Alaska, the scientists said: as pockets of soil collapse as the ice it contains melts, highways buckle, houses are destabilized and trees tilt crazily in a phenomenon known as "drunken forests" when the earth beneath them gives way.
"There's an interconnectedness about the Arctic," Lawrence said. "When sea ice retreats and retreats very rapidly it impacts other parts of the system, like warming temperatures over land. And warming temperatures over land can also accelerate the degradation of permafrost, particularly permafrost that's warm right now."
The research will be published on Friday in the journal Geophysical Research Letters.
Sea Ice Melt Could Cause More Warming in Arctic
Andrea Thompson, LiveScience.com Yahoo News 10 Jun 08;
The rapid retreat of Arctic sea ice observed in recent summers could triple the rate of warming over northern Alaska, Canada and Russia, a new study suggests. Such intensive warming could endanger sensitive ecosystems and human infrastructure in those regions.
It's the warm version of the snowball effect.
"Our study suggests that, if sea-ice continues to contract rapidly over the next several years, Arctic land warming and permafrost thaw are likely to accelerate," said study leader David Lawrence of the National Center for Atmospheric Research in Boulder, Colo.
The North Pole is a region of ice floating on the sea, an expanse of ice that in winter connects in some places with continental Arctic ice.
The new research was spurred by the record melt of Arctic sea ice last summer, which shrank to more than 30 percent below its average. Around the peak in ice melt, which occurred in September, air temperatures over land in the western Arctic were also unusually warm from August to October, reaching more than 4 degrees Fahrenheit (2 degrees Celsius) above the 1978-2006 average. This raised the question of whether or not these phenomena were related.
To answer that question, Lawrence and his team used simulations of sustained periods of rapid sea ice loss. The simulations showed that during such episodes, the rate of Arctic land warming is 3.5 times greater than the average 21st century warming predicted in global climate models.
While the warming was largest over the ocean, the simulations suggested that it could penetrate as far as 900 miles (1,450 kilometers) inland. They also indicated that this warming is particularly pronounced in the autumn months; a decade that sees rapid sea-ice loss could also see autumn temperatures rise by as much as 9 F (5 C) along Arctic coastlines.
Such accelerated warming could lead to rapid thaw of permafrost, the frozen soil that covers larger portions of the Arctic, especially in areas where the permafrost is already at risk from warming.
Thawing permafrost could further exacerbate global warming, because Arctic soils are believed to hold 30 percent or more of all the carbon stored in soils worldwide. Though researchers are unsure what would happen to this carbon when the soil thawed, it is possible that significant amounts of carbon dioxide or methane could be released into the already greenhouse-gas-enriched atmosphere.
As the permafrost thaws, it could also buckled highways, destabilize houses, and cause trees to lean at wild angles.
"An important unresolved question is how the delicate balance of life in the Arctic will respond to such a rapid warming," Lawrence says. "Will we see, for example, accelerated coastal erosion, or increased methane emissions, or faster shrub encroachment into tundra regions if sea ice continues to retreat rapidly?"
The study is detailed in the June 13 issue of the journal Geophysical Research Letters, and was funded by the U.S. Department of Energy and the National Science Foundation.
