Giant iceberg potential Arctic shipping hazard

by Randy Boswell, Canwest News Service, June 7, 2009

A billion-tonne iceberg that calved from a northern Greenland glacier last summer has drifted 2,000 kilometres into Canadian waters and is now stalking the southern coast of Baffin Island -- a potential shipping hazard that federal scientists are closely tracking by satellite and with a beacon placed directly on the frozen mass.

But experts monitoring the Petermann Ice Island -- named for the glacier it split from last July -- say they're bracing for the birth of a monster berg five times bigger that could break away from the same High Arctic source this summer.

If that colossal chunk of ice and snow remains whole after it heaves clear of Greenland's ancient Petermann Glacier, it would form a floating monolith about the size of B.C.'s Saltspring Island -- greater in area than New Brunswick's Grand Manan or Ontario's Wolfe Island, the largest of the Thousand Islands.

Officials with the Canadian Ice Service, the branch of Environment Canada that monitors ice conditions on the country's navigable waterways, is sharing data with a team of U.S. scientists to ensure an early warning when the glacier calves again.

It currently has a massive crack about one kilometre wide and 12 kilometres long -- a split that could produce a 160-km² ice island likely to track the same southward route down Davis Strait the earlier one did.

"In terms of another chunk of ice about to break off," a Canadian Ice Service spokeswoman told Canwest News Service, the service is "sharing RADARSAT-2 images" with U.S. researchers studying the Greenland glacier, who will in return provide Environment Canada with "advance warning of any impending breakup."

Ohio State University scientist Jason Box and other experts with the Byrd Polar Research Center first alerted the world last summer to the loss of a 29-km² ice island from Petermann.

Petermann is a 1,300-km² projection of ice down a Greenland fiord that constitutes the largest floating glacier in the northern hemisphere.

The breakaway iceberg was the billion-tonne colossus that drifted through Nares Strait between Ellesmere Island and Greenland en route to its current position along Baffin Island's southeastern shore, said ice service spokeswoman Sujata Raisinghani.

Since that ice island calved 11 months ago, it has shrunk to 12 km² and lost about half of its mass, she said.

"In keeping with our mandate to monitor ice conditions to protect the safety of mariners and their ships in Canada's navigable waters, we have been tracking the ice island's movement," she said. "During the past month, the ice island has been in a stationary position just north of the entrance to Frobisher Bay."

The ice service says Petermann Ice Island poses "no immediate danger to marine shipping," but added it will continue to be tracked in case it threatens to interfere with summer traffic in Canada's increasingly busy Arctic waters.

At the time of the 29-km² calving event, Box warned of the growing crack further up the glacier and the "imminent" possibility of a larger collapse.

"This crack is moving, and moving closer and closer to the front," he said at the time. "It's just a matter of time till a much larger piece is going to break off."

The collapse of several Arctic ice shelves in recent years have kept Canadian officials on alert for possible disruptions to shipping activity or danger to offshore oil platforms.

In 2005, a 66-km² chunk of the Ayles Ice Shelf on Ellesmere Island's northern coast broke free and began drifting south. Federal scientists kept a close watch on the resulting Ayles Ice Island as it tracked a worrisome route toward the Beaufort Sea, a hot spot for oil exploration.

But in August 2007, the 5 x 15 km slab turned down a dead-end channel between Meighen and Axel Heiberg islands, where scientists expected it to slowly break up -- probably over decades -- and become an anonymous part of the Arctic pack ice.

Last year, the Ellesmere Island ice shelves experienced unprecedented losses of about 200 km², sending more huge chunks drifting through Canada's Arctic waters.

One of the country's five remaining Arctic ice shelves -- the 4,500-year-old, 50-km² Markham Ice Shelf -- broke completely away from Ellesmere and drifted into the Arctic Ocean, the most dramatic sign yet of how rising temperatures and retreating sea ice are creating what one top scientist called "irreversible'' changes to the country's polar frontier.

Referring to last summer's loss of about 25% of the total area in Canada covered by ice shelves, Trent University ice expert Derek Mueller said: "These substantial calving events underscore the rapidity of changes taking place in the Arctic. These changes are irreversible under the present climate and indicate that the environmental conditions that have kept these ice shelves in balance for thousands of years are no longer present.''

In an interview last year with Canwest News Service, Canadian Ice Service director Douglas Bancroft warned that although the opening of Arctic sea ice in recent years holds the promise of more shipping in the Northwest Passage and other polar routes, the breakup of multi-year ice caused by record-setting warm temperatures could also pose an increased hazard for navigation.

Link to article: http://www.nationalpost.com/news/story.html?id=1672001