Beware of rising waters

Ice Shelf Collapse Sends Chill

Canada's North changing. Global warming suspected cause of huge breakup on Ellesmere Island.

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," said Warwick Vincent of Universite Laval, 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 making public details after piecing together what occurred using seismic monitors and Canadian and U.S. satellites.

They say the ice shelf collapse, suspected to have been caused by global warming, is the biggest in Canada in 30 years and is indicative of the transformation under way on Ellesmere, Canada's most northern land mass.

"We are seeing incredible changes," said 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."

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.

In 2002, one of Vincent's graduate students, Derek Mueller, discovered that 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 shelves are 90 per cent smaller than they were when Arctic explorer Robert Peary crossed them in 1906. And the Ayles ice shelf can be erased from Canada's maps.

"It no longer exists," Vincent said.

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 one hour for the ice shelf to calve off in the early afternoon of Aug. 13, 2005, Copland said. Low frequency "rumbling" and tremors were picked up on 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," Copland said.

"And then the ice drifted off."

Within an hour, the giant ice island was one kilometre offshore. It travelled west about 50 kilometres during the next few weeks and then moved east before freezing into sea ice about 15 kilometres offshore.

Copland has reconstructed what happened with Weir and Mueller, who is now at the University of Alaska in Fairbanks.

"We have a really good sequence of the ice shelf breaking up and then floating away," Copland said.

Vincent flew out from his base camp on northern Ellesmere by helicopter this year to have a first-hand look at the scene of the collapse.

"There was a huge amount of rubble associated with this breakup," Vincent said, explaining how the fjord is now full of ice blocks, "and then this vast ice shelf floating offshore."

The ice island is about 37 metres thick and measures roughly 15 kilometres by five kilometres. That's the size of a small city, or larger than 11,000 football fields. The island is now stuck in winter ice, but the researchers say it is only 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 toward 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," Copland said. He said two key factors appear to have triggered the breakup - the exceptionally warm temperatures on Ellesmere in summer last year,

3 degrees Celsius above normal, and unusually brisk winds that blew the summer pack ice offshore, exposing the Ayles shelf to waves and open water. Normally, the prevailing winds blow summer pack ice up against Ellesmere's ice shelves, where it acts as a buffer, protecting them from the sea.

The scientists say they can't prove human-induced climate change caused the Ayles shelf to break off, but they suspect global warming might be responsible.

"We can say it is consistent with the larger body of evidence indicating the climate is warming and predictions that the greatest effects are likely to take place at high latitudes," Vincent said. He noted that the Ayles disintegration is the most recent of several abrupt changes on Ellesmere.

"Suddenly, lakes that existed aren't there any more, ice dams collapse, ice shelves break up," Vincent said.

"These are big changes."

Researchers say there are many more changes in store. Last week, a Canada-U.S. team predicted that the Arctic Ocean could be devoid of summer ice as early as 2040 and possibly sooner.

Original article posted here.