Giant Ice Shelf Breaks Off in Canadian Arctic
Richard A. Lovett
for National Geographic News
|December 29, 2006|
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.
"We can't say that this [specific] event is due to global warming, but it definitely fits the long-term trend."
The summer of 2005, Copland said, had the lowest amount of Arctic Ocean sea ice ever recorded.
Pack ice normally buffers the ice shelf from ocean movement. But with little ice and strong offshore winds, waves were able to batter the ice shelf, weakening it.
In addition, 2005 was the warmest summer recorded on Ellesmere Island since 1960, with temperatures about 3.8°F (2.1°C) above average.
And the ice shelf breakup wasn't the only geologic disturbance on the island that summer.
Antoni Lewkowicz, a geography professor at the University of Ottawa, happened to be on the island when the ice shelf disintegrated, although he was unaware of the event at the time.
For nearly 20 years Lewkowicz has been studying landslides triggered by melting permafrost.
The overall warm summer thawed out the island significantly, he said, and a week of strong sun at the end of July set off massive numbers of landslides.
"You need a blast of heat," he said. "And that's what happened—a week of clear weather and warm temperatures, which triggered a whole bunch of landslides literally all around us."
In one 3.5-square-mile (9-square-kilometer) tract he counted 50 landslides during the warming period.
"So there were reactions to that warm period on the land as well," he said.
The broken ice shelf and Lewkowicz's landslides are important indicators of global climate change and its effects on the polar ice caps.
Earlier this month scientists reported that global warming may mean that the Arctic Ocean's summer sea ice will be completely gone by 2040.
And recent studies have shown that a loss of Arctic ice is causing polar bear populations to plummet, leading to a proposal to include the bears on the U.S. endangered species list.
Copland adds that the ice shelves are valuable because they offer a variety of historical and ecological insights.
Creatures that survive in such extreme environments, for example, could be analogues for life on other planets.
Arctic ice shelves are "not as sexy as polar bears," Copland said.
"But these are very unique environments, and we just lost one of them."
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
|© 1996-2008 National Geographic Society. All rights reserved.|