Arctic Ocean sea ice has experienced another severe meltdown this year, with the approaching end-of-summer minimum representing the third-biggest thaw since satellite monitoring began about 30 years ago.
This year's retreat from a winter maximum of about 15 million square kilometres to a September coverage area of just five million square kilometres also means that the four greatest melts since satellite measurements began in the late 1970s have occurred in the past four years.
In a report released Tuesday, the U.S. National Snow and Ice Data Center described the opening of the Northwest Passage through Canada's Arctic islands and the "unusually fast" melting of ice in the Beaufort Sea as highlights of another extensive circumpolar thaw that has all northern nations — including Canada — scrambling to cope with increased Arctic ship traffic and to plan for potential oil and gas development.
"There are claims coming from some communities that the Arctic sea ice is recovering, is getting thicker again," Mark Serreze, director of the Colorado-based centre, told Postmedia News on Wednesday.
"That's simply not the case. It's continuing down in a death spiral."
Arctic sea ice typically reaches its minimum annual extent in mid-September.
In September 2007, scientists and governments around the world sounded alarms when an extreme meltdown reduced the ice cover from a winter maximum of about 14 million square kilometres to an end-of-summer minimum of just over four million square kilometres.
Since then, summer ice cover has repeatedly fallen below the 30-year average minimum of about seven million square kilometres.
Serreze said this year's retreat offers further evidence of the "overall downward trend" but only tells half the story of the declining Arctic ice cover.
Scientists have also determined that along with the overall shrinkage in ice area, the polar region's oldest and thickest slabs are increasingly being replaced by younger and thinner ice — a phenomenon that's widely expected to result in ice-free Arctic summers in the coming years.
"Every bit of evidence we have says the ice is thinning," said Serreze.
"That means there's less energy needed to melt it out than there used to be."
Sea ice trends, he cautioned, will continue to be affected by natural variations in temperature and wind patterns throughout the circumpolar world.
But Serreze said the overall pattern is unmistakable: "The decline in the extent of ice — the square kilometres — is being attended by a decrease in the volume of ice."
Canada and the four other Arctic Ocean coastal nations — Russia, the U.S., Denmark and Norway — have pledged to co-operate in creating new search-and-rescue and environmental protection regimes to manage increased shipping, tourism and economic development in the melting Arctic.
This summer's stranding of an Arctic adventure cruise ship and a second vessel carrying millions of litres of diesel fuel has underlined the growing risk of a tourism emergency or environmental catastrophe as once-frozen shipping lanes become unlocked in Canada's Far North.
Meanwhile, Canadian and U.S. scientists have been collaborating for the third straight year on mapping the Arctic Ocean seabed north of the Yukon-Alaska border, part of a bid by each country to secure huge new swaths of undersea territory under a UN treaty.
The push for extended continental shelves in the Arctic is considered potentially lucrative because it's estimated that up to one-quarter of the world's untapped oil and gas reserves can be found in the region.
The prospect of offshore petroleum operations in an increasingly accessible Arctic — despite growing environmental concerns fuelled by the Deepwater Horizon disaster in the Gulf of Mexico — continues to shape the Canadian government's northern economic agenda.
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