AN ancient ice shelf has cracked off northern Ellesmere Island, creating an enormous, 66-square-kilometre ice island and leaving a trail of icy blocks in its wake.
"It really is incredible," says Warwick Vincent of Laval University, one of the few people to have laid eyes on the scene. "It's like a cruise missile has come down and hit the ice shelf."
The breakup was so powerful, earthquake monitors 250 kilometres away picked up the tremors as the 3,000- to 4,500-year-old shelf tore away from its fjord on Ellesmere.
It broke up 16 months ago, but no one was present to see it. The scientists say they are only now releasing details after piecing together what occurred using seismic monitors and Canadian and U.S. satellites.
They say the ice shelf collapse is the biggest in Canada in 30 years and is indicative of the transformation underway on Ellesmere, Canada's most northern landmass.
"We're seeing incredible changes," says Vincent, whose group is studying the island's disappearing ice shelves and their unique ecosystems.
"People talk of endangered animals -- well, these are endangered landscape features, and we're losing them," says Vincent. In 2002, his graduate student Derek Mueller discovered Ellesmere's Ward Hunt Ice Shelf had cracked in half. The researchers have also seen the sudden collapse of ice dams and the draining of 30-kilometre-long lakes into the sea.
The Ayles Ice Shelf was one of six ice shelves left in Canada, remnants of a vast icy fringe that used to cover the top end of Ellesmere. Scientists consider the Canadian shelves, located about 800 kilometres south of the North Pole, sentinels that reflect the accelerating change in the Arctic.
The shelves are 90 per cent smaller than they were when Arctic explorer Robert Peary crossed them in 1906. And the Ayles ice shelf can now be erased from Canada's maps. "It no longer exists," says Vincent.
Laurie Weir, of the federal Canadian Ice Service in Ottawa, was poring over images from the RADARSAT satellite when she noticed the shelf had broken away. She passed the information on to Luke Copland, head of the new global ice lab at the University of Ottawa, who led the effort to determine what had happened.
It turned out it took less than an hour for the ice shelf to calve off in the early afternoon of Aug. 13, 2005, says Copland. Low frequency "rumbling" and tremors were picked up on Alert's earthquake monitors, and Canadian and U.S. satellites captured images of the shelf cracking and breaking away.
"If you were standing right on the edge of the shelf, there'd have been this huge 15-kilometre crack as far as you could see in both directions," says Copland. "And then the ice drifted off." Within an hour, the giant ice island was a kilometre offshore. It travelled west about 50 kilometres over the next few weeks, and then moved east before freezing into the sea ice about 15 kilometres offshore.
The ice island is about 37 metres thick and measures roughly 15 kilometres by five kilometres. The island is now stuck in the winter ice, but the researchers believe it is just a matter of time before it is freed and floats away. They say the ice island could become a potential hazard to navigation and oil and gas extraction if it sails south towards the Beaufort Sea.
But for now, it is a monument to change.
"This is the biggest event since the '80s in terms of ice-shelf loss, " says Copland. He says two key factors appear to have triggered the breakup -- the exceptionally warm temperatures on Ellesmere in the summer of 2005, which were three degrees Celsius above normal, and unusually brisk winds that blew the summer pack ice offshore, exposing the Ayles shelf to waves and open water.
The scientists say they can't prove human-induced climate change caused the Ayles shelf to break off, but they suspect global warming may be responsible.
-- CanWest News Service
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