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Science
| 03/26/15

Arctic sea ice reaches lowest extent on record

TCE

When Arctic sea ice reached its maximum range this year, it clocked in at the lowest extent in the satellite record, prompting domestic and international calls for urgent action. The United States (US) National Snow & Ice Data Center (NSIDC) announced last week that the annual maximum was 14.54 million square kilometres, roughly 1.10 million square kilometres less than the thirty-year (1981-2010) average, and 130,000 square kilometres less than the previous low that occurred in 2011.

This winter’s date of maximum ice coverage also came over a fortnight earlier—25 February—than the three-decade average of 12 March. The researchers note that the date of the maximum does vary, hitting as early as 24 February back in 1996 and as late as 2 April in 2010. A late surge in ice growth is still possible over the next two to three weeks, say the researchers, but this is unlikely to beat February’s top mark. On average, the extent of Arctic winter sea ice cover has diminished by 4.5 percent per decade; this February’s maximum areal coverage was 13% below the 16.5 million square kilometres observed in March 1979 at the beginning of the satellite-based monitoring era.

The NSIDC scientists say that this year’s weak maximum extent is the result of exceptionally warm conditions over the Pacific side of the Arctic—itself a product of an unusual configuration of the jet stream in February—and low atmospheric pressure between Iceland and southern Greenland and into the Barents Sea from mid-February to mid-March, which led to the arrival of warm surface winds from the south. Meanwhile on the other side of the world, Antarctic sea ice shrank on February 20 to the fourth smallest summer minimum in the satellite record. What is crucial for the public to understand, say the researchers, is how climate change produces both hotspots of unusual warmth and unusual cold. The localised Arctic warmth is part of a much broader area of atypically warm conditions reaching across much of northern Eurasia, Alaska and down through British Columbia into the western part of the US. At the same time, bitterly cold and snowy conditions have stuck around across eastern North America. Both these opposing patterns of warmth and cold, and the low ice extent are linked to an unusual jet stream pattern, with warm air extending further north than normal on the western side of North America, and Arctic air looping southwards over Ontario, Quebec and the US northeast. Reacting to the news, the federal opposition New Democrats repeated their (denied) 2012 call for an emergency debate in parliament over the ramifications. Environment critic Megan Leslie said that the record low sea ice extent has implications across a range of policy areas. “”This is an actual emergency,” she said. “With the sea ice level changes, we’re seeing unprecedented threats to the livelihoods and the lives of northern people, to our economy, to our security.”

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