Huge chunk snaps off storied Arctic ice shelf

A four-square-kilometre chunk has broken off Ward Hunt Ice Shelf - the largest remaining ice shelf in the Arctic - threatening the future of the giant frozen mass that northern explorers have used for years as the starting point for their treks.

Scientists say the break, the largest on record since 2005, is the latest indication that climate change is forcing the drastic reshaping of the Arctic coastline, where 9,000 square kilometres of ice have been whittled down to less than 1,000 over the past century, and are only showing signs of decreasing further.

"Once you unleash this process by cracking the ice shelf in multiple spots, of course we're going to see this continuing," said Derek Mueller, a leading expert on the North who discovered the ice shelf's first major crack in 2002.

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"We see this in a variety of indicators, including ... a gradual increase in air temperatures in this area. Each year it seems we're crossing a new threshold of environmental change in this area of the world."

Dr. Vincent said it's important to note that the Ward Hunt ice break is "small compared to what we've seen in the past."

Indeed, the largest ice break recorded in recent time was significantly larger: In 2005, the Ayles Ice Shelf, one of six in existence in Canada at the time, broke off in its entirety, rendering a 66-square-kilometre ice island that floated out to sea.

Still, the latest break "indicates ongoing change in this very sensitive area," Dr. Vincent said.

Dr. Mueller, whom Dr. Vincent calls the pre-eminent expert on Ward Hunt Ice Shelf, says he's concerned that the ice shelves will disappear completely.

"The take-home message for me is that these ice shelves are not regenerating," he said. "If we're looking at an indicator of whether climate is to blame, it's really the lack of regeneration that convinces me. They're breaking away so rapidly that there's no hope of regeneration," he said, adding that is "pretty strong evidence that suggests this is related to global warming."