Last September, at the end of the northern hemisphere summer, the Arctic Ocean’s icy cover shrank to its lowest extent on record, continuing a long-term trend and diminishing to about half the size of the average summertime extent from 1979 to 2000.
During the cold and dark of Arctic winter, sea ice refreezes and achieves its maximum extent, usually in late February or early March. According to a NASA analysis, this year the annual maximum extent was reached on Feb. 28 and it was the fifth lowest sea ice winter extent in the past 35 years.
The new maximum -5.82 million square miles (15.09 million square kilometers)- is in line with a continuing trend in declining winter Arctic sea ice extent: nine of the ten smallest recorded maximums have occurred during the last decade. The 2013 winter extent is 144,402 square miles (374,000 square kilometers) below the average annual maximum extent for the last three decades.