Thursday, December 28, 2006
Giant ice shelf breaks free from Canadian Arctic
Updated Thu. Dec. 28 2006 7:54 PM ET
A giant ice shelf the size of 11,000 football fields has snapped free from Canada's Arctic, leaving a trail of icy boulders floating in its wake.
The mass of ice broke clear from the coast of Ellesmere Island, about 800 kilometres south of the North Pole. Warwick Vincent of Laval University, who studies Arctic conditions, travelled to the newly formed ice island and couldn't believe what he saw. "It was extraordinary," Vincent said Thursday, adding that in 10 years of working in the region he has never seen such a dramatic loss of sea ice.
"This is a piece of Canadian geography that no longer exists."
The collapse was so powerful that earthquake monitors 250 kilometres away picked up tremors from it.
Scientists say it is the largest event of its kind in 30 years and point their fingers at climate change as a major contributing factor.
"We think this incident is consistent with global climate change," Vincent said, adding that the remaining ice shelves are 90 per cent smaller than when they were first discovered in 1906.
"We aren't able to connect all of the dots . . . but unusually warm temperatures definitely played a major role."
The ice shelf actually broke up 16 months ago, but no one witnessed the dramatic event.
Laurie Weir, who monitors ice conditions for the Canadian Ice Service, was poring over satellite images when she noticed that the shelf had split and separated.
Weir notified Luke Copland, head of the new global ice lab at the University of Ottawa, who initiated an effort to find out what happened.
Using U.S. and Canadian satellite images, as well as data from seismic monitors, Copland discovered that the ice shelf collapsed in the early afternoon of Aug. 13, 2005.
"These ice shelves can break up really quickly, perhaps more quickly than we thought they could do in the past," he said.
"Within an hour we could see this entire ice chunk just disconnect and float away."
Within days, the floating ice shelf had drifted a few kilometres offshore. It travelled west for 50 kilometres until it finally froze into the sea ice in the early winter.
Derek Mueller, a polar researcher with Vincent's team, saw that Ellesmere's Ward Hunt Ice Shelf had cracked in half in 2002. He also saw that sea ice, which creates a buffer zone around ice shelves, was approaching lower and lower levels.
"These ice shelves get weaker and weaker as the temperature rises," he said.
"And the summer of 2005 had a combination of high temperatures and strong winds that probably blew the sea ice away, making this ice shelf much more vulnerable."
The Ayles Ice Shelf, roughly 66 square kilometres in area, was one of six major ice shelves remaining in Canada's Arctic.
They are packed with ancient ice that dates back over 3,000 years, and scientists like Vincent treat their loss as a sign that the global climate is crossing an unprecedented threshold.
"We're seeing the tragic loss of unique features of the Canadian landscape," he said.
"There are microscopic organisms and entire ecosystems associated with this ice, so we're losing a part of Canada's natural richness."
Meanwhile, the spring thaw may bring another concern as the warming temperatures could release the ice shelf from its Arctic grip.
Prevailing winds could then send the ice island southwards, deep into the Beaufort Sea.
"Over the next few years this ice island could drift into populated shipping routes," Weir said.
"There's significant oil and gas development in this region as well, so we'll have to keep monitoring its location over the next few years."
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