Thursday, 28 January 2010

Melting Arctic Ice: What Satellite Images Don't See - Ice "full of holes, like Swiss cheese."

RT @Northern_Clips: Melting #Arctic Ice: What Satellite Images Don't See - TIME Ice "full of holes, like Swiss cheese.


For scientists studying the health of Arctic sea ice, satellite observations are absolutely essential for providing the big picture. It was satellites that revealed in September 2007 a record minimum ice coverage in the region — the result of a massive summer melt. And it was satellites that showed in 2008 and 2009 the modest recovery of late-summer Arctic ice that suggested to some that the specter of a totally ice-free polar ocean might be somewhat less imminent than feared.

But those high-altitude observations need occasional reality checks from scientists down on the surface. It was during one such on-the-ground research expedition last fall that David Barber, an Arctic climatologist at the University of Manitoba, got an unwelcome surprise.

Barber was aboard the Canadian research icebreaker Amundsen, checking on ice in the Beaufort Sea north of Alaska and Western Canada. The ship was well inside a region the satellites said should be choked with thick, multiyear-old ice. "That's pretty much a no-go zone for an icebreaker of the Amundsen's size," says Barber. But the ship kept going, at a brisk 13 knots — its top speed in open water is 13.7 knots — and even when it finally reached thick ice, he says, "we could still penetrate it easily."

In short, as Barber and his colleagues explain in a recent paper in Geophysical Review Letters, the analysis of what the satellites were seeing was wrong. Some of what satellites identified as thick, melt-resistant multiyear ice turned out to be, in Barber's words, "full of holes, like Swiss cheese. We haven't seen this sort of thing before."

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