AN area of ice covering about 18sqkm has broken off Canada’s largest remaining ice shelf.
|The ice floe drifts off the Ward Hunt shelf|
Trent University researcher Derek Mueller said yesterday he would not be surprised if more ice broke off during the northern summer from the Ward Hunt Ice Shelf, a vast frozen plain off the north coast of Ellesmere Island in Canada’s far north.
In a development consistent with climate change theories, the enormous 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 northern spring, a patrol of Canadian Rangers found the weakness had spread into an extensive network of cracks, some 18km long and 40m wide. The crack-riddled 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 once entirely ringed by a single enormous ice shelf that broke up in the early 1900s.
At 440sqkm in size and 40m thick, the Ward Hunt shelf is the largest of those remnants — even bigger than the Antarctic shelf that collapsed this year and seven times the size of the Ayles Ice Shelf that broke off in 2005 from Ellesmere’s western coast.
Despite a period of stability in the 80s, the Ward Hunt shelf and its characteristic corrugated surface has been declining since the 30s, Dr Mueller said. Its southern edge has lost 18sqkm over the past six years.
Dr Mueller did not blame the Ward Hunt breakup specifically on climate change, but said it was consistent with the theory.
“We’re in a different climate now,” he said.
It’s the same all over the Arctic, said Gary Stern, co-leader of a major international research program on sea ice.
Speaking from the Coast Guard icebreaker Amundsen in Canada’s north, Professor Stern said the Ward Hunt breakup was related to what he was seeing thousands of kilometres away.