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Shrinking Arctic Ocean sea ice signals climate change

Global warming may have accelerated the irreversible loss of ice shelves that are thousands of years old, say scientists.

By Peter N. SpottsStaff writer of The Christian Science Monitor / September 4, 2008

Fractured: The Ward Hunt Ice Shelf along the coast of Ellesmere Island in northern Canada is rapidly disintegrating, endangering unique microbial ecosystems.

Denis Sarrazin/Center for Northern Studies/Reuters

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Key portions of Earth’s cryosphere are in deep trouble. So far this summer, Arctic Ocean sea ice has shrunk to its second-lowest extent on record as ice shelves along Canada’s northernmost islands are disintegrating at a rapid pace. A new report from the United Nations Environment Program and the World Glacier Monitoring Service notes that the melt rate for glaciers the service uses as reference sites appears to have doubled since 2000. The resulting increase in open water is expected to have a wide-ranging impact on global warming.

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“These are huge areas that are changing,” says Luke Copland, who heads the Laboratory for Cryospheric Research at the University of Ottawa, referring to the ice declines in the Arctic.

People can debate the causes behind what’s happening in the Arctic, he says, “but what we can’t debate is the fact that things are changing, and they’re changing really fast.” Moreover, the changes are irreversible under today’s climate regime, adds Derek Mueller, a polar scientist at Trent University in Peterborough, Ontario.

On Tuesday, Dr. Mueller and his colleagues reported that in early August, the 19-square-mile Markham Ice Shelf broke free of its moorings on the northern coast of Ellesmere Island. It’s now an ice island nearly the size of Manhattan floating freely in the Arctic Ocean.

Another of Canada’s four remaining ice shelves has lost 60 percent of its extent, while a third shelf continues to disintegrate. The accumulated loss for the summer amounts to an area of ice more than three times the size of Manhattan, or some 23 percent of the area that existed heading into summer.

As of Aug. 26, the total seasonal loss of Arctic Ocean sea ice was slightly more than 2 million square miles. That’s 760,000 square miles below the 1979-2000 average, according to the National Snow and Ice Data Center in Boulder, Colo.