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Arctic sea ice melting faster than expected

If the pattern continues, warming effects could reach up to 900 miles inland, melting permafrost

By Peter N. SpottsStaff writer of The Christian Science Monitor / June 12, 2008

A polar bear mother and her two cubs walk along the shore of Hudson Bay in Manitoba near Churchill, Canada. In May, the U.S. Interior Department declared the polar bear a threatened species saying it must be protected because of the decline in Arctic sea ice from global warming.

AP Photo/THE CANADIAN PRESS/Jonathan Hayward, File


Arctic Ocean sea ice – one of the most visible indicators for global warming – may be headed for another record-breaking summer decline.

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If the pattern continues, new research suggests, its warming effect could reach up to 900 miles inland, melting permafrost and potentially altering weather patterns at lower latitudes.
As of June 7, preliminary data show that the vast expanse of ice at the top of the world is some 55,800 square miles smaller than it was on the same date last year, according to University of Colorado researcher Sheldon Drobot. In May, sea-ice extent was slightly large than in May 2007. But the melt rate during the month – some 3,000 square miles a day – was faster, according to the National Snow and Ice Data Center in Boulder, Colo.

The ice’s seasonal shrinkage in 2007 smashed records, reaching a September minimum of 2.6 million square miles – some 23 percent smaller than the previous record, set in 2005. If it sets another record this year, it would mark the fifth season of record declines since 1998.

“The next few weeks should be quite instructive, and by mid July we ought to have a very good sense of how things are shaping up,” says Dr. Drobot, who is using satellite data on ice extent to develop forecasts of seasonal changes in Arctic Ocean ice cover.

Typically, bright sea ice sends sunlight streaming back into space, keeping things relatively cool at the surface. Leftover ice at the end of the summer forms the foundation on which ice rebuilds during fall and winter. Over successive seasons, older, multi-year ice grows thicker and more resistant to a meltdown in subsequent summers than thin, single-year ice. Last year’s record decline, however, left a shaky foundation. Some 63 percent of the ice is younger than average, while only 2 percent is older than average, according to Drobot.

The prospect of more open water in the Arctic Ocean in summer would be a boon to shipping interests, greatly reducing the sailing time between Europe and Asia, for instance. Indeed, the prospect of increased shipping is a key driver for Drobot’s forecasting research. And countries bordering the Arctic Ocean are trying to stake their claim to extended territorial waters under the Law of the Sea Treaty to exploit resources believed to lie beneath the Arctic Ocean floor.

But from a climate standpoint, more open water during summer translates into warmer temperatures, since the dark seawater absorbs sunlight, stores the heat, then slowly releases it. This played a large role in last year’s summer melt-off, explains Don Perovich, a researcher with the US Army Corps of Engineers Cold Regions Research and Engineering Laboratory in Hanover, N.H.