More melting news

I spent five years of my life in Canada's Arctic and not a day goes by that I'm not reminded just how powerful an impression those years left made on me. When I read the latest news on arctic sea-ice extent, I wish more people would recognize just how important what happens up there is to the rest of the planet. Now, I know fellow ScienceBlogger William Connelly is convinced "nothing much going on with sea ice at the moment." But that's not what I see in the latest graphs from the National Snow and Ice Data Center.

Just a couple of years ago, the scientists who study such things thought it would be at least 50 or 60 years before we'd be facing an ice-free summer in the Arctic Ocean. But with every season and every new research finding, that number shrinks.

Last year I wrote about how the the time-frame for an ice-free Arctic summer had shrunk from 40 years to 20 to 13. That was then.

The latest prediction has all the summer ice melting by 2013. That's just five more winters from now. Last year saw a record low for sea-ice extent (areas with at least 15% ice cover). Until this past week, the experts at the NSIDC were calling for a lower than average year, but not another record.

But one of things you learn living in the Great White North is just how fast conditions can change. Now, says the center's Mark Serreze, "It is a neck-and-neck race between 2007 and this year over the issue of ice loss." Why? As the NSIDC web report explains, it's because so much ice melted last year that most of what refroze is less than a year old, making much more less of the usual "multi-year" ice.

The Arctic sea ice is in a condition we have not seen since satellites began taking measurements ... thin first-year ice dominated the Arctic early in the melt season. Thin ice is much more vulnerable to melting completely during the summer; it seems likely that we will see a faster-than-normal rate of decline through the rest of the summer.

This is important because the loss of arctic ice is one of those climate "tipping points" that could trigger widespread changes elsewhere in the planetary ecosystem and could be impossible to reverse on human time scales. Tim Lenton of the University of East Anglia, who has been giving tipping points a lot of thought over the last few years, recently summarized his latest thinking thusly:

A more convincing case can be made that climate warming may have caused the Arctic sea-ice to pass a tipping point. Certainly the area coverage of both summer and winter Arctic sea-ice are declining at present, summer sea-ice more markedly, and the ice has thinned significantly over a large area. Elegant analysis has shown that positive ice-albedo feedback (the warming due to changing from reflective ice to dark ocean surface) dominates over external forcing (the global warming signal) in causing the thinning and shrinkage since around 1988. This suggests the system may already be undergoing a non-linear transition toward a different state with less Arctic sea-ice (perhaps none in summer).

For "non-linear transition" read "very, very fast." If that's the case, all bets are off on just how rapidly climate change will be upon the rest of us. Lenton goes on to write that "If any of the above inferences are correct and these systems have already passed a tipping point then there is little we can do about it except try and adapt."

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