Wednesday, July 30, 2008

Break-up after 3000 years

Edmonton, Canada 
The Age, July 31, 2008

A CHUNK of ice about 18 square kilometres in size broke off Canada's largest remaining ice shelf last week, a researcher says.

Trent University's Derek Mueller said he wouldn't be surprised if more ice broke off this summer from the Ward Hunt Ice Shelf, a vast frozen plain off Ellesmere Island in Canada's far north. In a development consistent with climate change theories, the huge icy plain broke free some time last week and began slowly drifting into the Arctic Ocean. The piece had been a part of the shelf for 3000 years.

A crack in the shelf was first spotted in 2002. Last spring Canadian Rangers found the weakness had spread into an extensive network of cracks, some 40 metres wide and 18 kilometres long. Formed by accumulating snow and freezing meltwater, ice shelves are large platforms of thick, ancient sea ice that float on the ocean's surface.

Ellesmere Island was once entirely ringed by a single enormous ice shelf that broke up in the early 1900s. At 440 square kilometres in size and 40 metres thick, the Ward Hunt shelf is the largest of those remnants - even bigger than the Antarctic shelf that collapsed this year.

Despite a period of stability in the 1980s, the shelf has been steadily declining since the 1930s, said Dr Mueller, who would not specifically blame climate change, but said the break-up was consistent with the theory.


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