Categorized | Alaska, Climate Change

Arctic Sea Ice Continues Decline

Arctic sea ice continues its precipitous decline: as we near the end of the summer ice-melt season, all indications suggest that the extent of sea ice has fallen to record or near-record lows this year. Satellite measurements by the National Snow and Ice Data Center found that the sea-ice extent was 1.68 million square miles, just 70,000 square miles above the all-time record low, set in 2007. That may seem like a substantial cushion over the minimum, but it’s a far cry from the 1979-2000 average September minimum of nearly 3 million square miles. NSIDC won’t be able to pinpoint the final minimum until the sea ice begins to re-form, but the 2011 extent is already below the previous second- and third-place years, 2010 and 2008. However, they report the rate of melt is slowing and might not surpass their records for 2007. That’s the good news.

The bad news is that another ice-tracking team, at the University of Bremen in Germany, reports that their measurements show 2011 ice extent reached the lowest extent that they have ever recorded, at 1.64 million square miles (Bremen’s measurement for 2007 was 1.65 million square miles). The Bremen team’s methodology differs from NSIDC’s, hence the slight differences in their figures. But the two groups are close enough to be clear that the Arctic is melting, and fast. And that’s not the worst news.

The worst news is that the trend in Arctic ice VOLUME is even more dramatic than the trend in area. The Polar Science Center in Seattle estimates that the current trend in sea ice volume is running well below 2007, even though the two years are running practically neck-and-neck on extent. The sharp decline in volume means that the ice that is there is thinner than in the past, and therefore more prone to melting in the future.

In 2007 the Intergovernmental Panel on Climate Change noted that Arctic sea ice had declined 2.7% per decade over the past 30 years and warned that “In some projections, arctic late-summer sea ice disappears almost entirely by the latter part of the 21st century.” The IPCC may have been overly optimistic: if ice continues to be lost at current rates, we could see complete loss of summer ice by 2040. .  And it’s that overall trend – not whether this year is the lowest or second lowest – that spells big trouble for Arctic wildlife like polar bears.

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- who has written 22 posts on dotWild.

Aimee Delach is a Senior Policy Analyst at Defenders of Wildlife. Aimee develops policies to help land managers and decision-makers incorporate climate change threats into efforts to protect wildlife and habitats.

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dotWild is the blog of scientists and policy experts at Defenders of Wildlife, a national, nonprofit membership organization dedicated to the protection of all native animals and plants in their natural communities.