The Arctic saw a record loss of summer sea ice in 2012, and the 2013 melt is off to a faster start than a year ago. Another record is uncertain, but warming has sapped the ice's staying power.
After a record loss of summer sea ice in the Arctic Ocean last year, the 2013 melt season has begun at the top of the world, with ice vanishing in April at a faster pace than it did this time last year.
Summer sea ice – a key player in Earth's climate system and one whose decline is widely taken as a prominent sign of global warming – has been shrinking in extent since satellites first started to build a consistent record of the ice in late 1978. Ice losses in 2007 set a melt-season record, only to be eclipsed by last year's decline. Ice volume and thickness also have been declining during the past 34 years.
Whether the start to the 2013 thaw presages another record melt is unclear. Sketching expectations for the end of the melt season based on preseason indicators and one month's activity can be as dicey as predicting that the Boston Red Sox, with the best record in baseball coming out of April, will sweep the World Series next fall.
At the least, ice conditions entering this year's melt season appear to have set the stage for another significant retreat, compared with the 1979-2000 average.
After ice losses set the previous record in 2007, summer ice-extent recovered somewhat in each of the next three years, notes Claire Parkinson, a researcher studying climate and polar sea ice at NASA's Goddard Space Flight Center in Greenbelt, Md.
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