Sea ice cover in the Arctic appears to have reached its maximum extent for the year, and according to scientists with the National Snow and Ice Data Center, that extent ties 2006 for the lowest on record.
Watching a time-lapse movie of sea ice as it waxes and wanes over the course of a year is a little like watching a lung breathe in and breathe out. Over the fall and winter months, it steadily expands until it achieves its greatest extent – generally somewhere in March – and then it retreats until it reaches its lowest area, generally in September.
As Arctic temperatures warm, particularly in summer, the minimum sea ice extent has decreased precipitously. It is presently declining by 11.5 percent per decade relative to the 1979-2000 average. That decline has in turn affected sea ice recovery in the winter, as the ice that reforms is now younger and thinner, and thus less likely to persist. However, because the Arctic remains an extremely cold environment in the winter months, winter sea ice decline is less than in summer: about 3 to 4 percent per decade since 1979, when satellite measurements began.
Since the start of the satellite record, the maximum Arctic sea ice extent has occurred as early as February 18 and as late as March 31, with an average date of March 6. This year, it appears to have reached its maximum on March 7. At 14.64 million square kilometers (5.65 million square miles), the extent was 1.2 million square kilometers (471,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles), and equal to 2006 for the lowest maximum extent in the satellite record.
NSIDC will publish a full analysis of the 2010-11 winter season, and graphics comparing this season to the long-term record, in early April.
Photograph by Andy Mahoney/NSIDC