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Friday, August 1, 2008

Climate fear as giant ice sheets break off Arctic shelf

A chunk of ice is shown drifting after it separated from the Ward Hunt Ice Shelf in Canada

(Sam Soja/The Canadian Press/AP)

Scientists say the break-up of the Ward Hunt shelf is consistent with climate change theories

Giant sheets of ice measuring over seven square miles have broken off the largest remaining ice shelf in the Canadian Arctic, in a development consistent with climate change predictions.

Officials said that the chunks of ice split off the Ward Hunt Ice Shelf off Ellesmere Island last week, forming two floating islands of 1.9 and 5.4 square miles. More could follow later this year, they warned.

It was the largest fracture of its kind since the nearby Ayles ice shelf - roughly the size of Manhattan at 25 square miles - broke away in 2005.

Scientists had already identified deep cracks in the Ward Hunt shelf, which measures around 155 square miles. The shelf is one of five along Ellesmere Island in the northern Arctic.

“Because the break-off occurred between two large parallel cracks they’re thinking more could go this summer before the freeze sets in,” Trudy Wohlleben of the Canadian Ice Service said.

Asked to be more specific, she said: “More could be a piece as large as the Ayles ice shelf.”

Some experts stressed that the event should not be totally attributed to climate change.

“The break-off is consistent with other changes we’ve seen in the area, such as the reduction in the amount of sea ice, the retreat of the glaciers and the break-up of other ice shelves,” Ms Wohlleben said. However the trigger for the final break-off was likely a strong wind from the south, she added.

Derek Mueller, an Arctic ice shelf specialist at Trent University in Ontario, said that rising temperatures meant shelves were not being reinforced.

“We’re in a different climate now,” he said. “It’s not conducive to regrowing them. It’s a one-way process.”

He said he was concerned by the rapidity of changes in the High Arctic over the last few years.

“It’s a bit of a wake-up call for those people who aren’t yet affected by climate change that there are places on earth that are, and the same could be true for them (these people) if you fast-forward a decade or two or three,” he said.

The shelf, which measures 170 square miles - larger than the Antarctic shelf which collapsed earlier this year - began to form over 4000 years ago, scientists believe. A crack was first spotted in 2002 and last spring a patrol of Canadian Rangers found the weakness had spread into an extensive network of cracks, some 40 metres wide and 11 miles long. The fracture-ridden section of ice was like a jigsaw puzzle, with the pieces held in place only by each other.

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 onceentirely ringed by a single enormous ice shelf that broke into five in the early 1900s. Ward Hunt was the largest of those remnants.

Original here

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