for National Geographic News
A huge Canadian ice shelf 500 miles (800 kilometers) from the North Pole has disintegrated, leaving a large floating island of ice stranded 30 miles (48 kilometers) offshore, scientists reported yesterday.
The entire 25.5-square-mile (66-square-kilometer) Ayles Ice Shelf broke free from the northern coast of Ellesmere Island on August 13, 2005 (map of Canada).
The event registered as a small earthquake on instruments stationed 150 miles (250 kilometers) away, Warwick Vincent of Quebec's Laval University told the CanWest News Service.
"It's like a cruise missile came down and hit the ice shelf," Vincent said. "It no longer exists."
The breakup was spotted on satellite photos shortly after it occurred, but scientists have held back until now to make an announcement.
"We've spent the last year reconstructing exactly what happened," said Luke Copland, a geographer with the University of Ottawa in Ontario, Canada.
Sixteen months of study led Copland and colleagues to the conclusion that several factors were at work, mostly related to global warming.
Ice shelves are floating tongues of glaciers that fill bays in the Arctic and Antarctic. The shelves are attached to land and are much thicker than pack ice—freely floating masses of sea ice.
The Ayles ice shelf was believed to be 3,000 to 4,500 years old.
Before the breakup the Canadian Arctic had six ice shelves.
"Now there are five," Copland said. In the past hundred years, he added, Canada's ice shelves have shrunk by 90 percent.
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