Editor’s note: Scientists are concerned the Arctic Ice Cap is shrinking. Based on data from the National Snow and Ice Data Center (NSIDC) at the University of Colorado, sea ice reached its maximum on February 25 before beginning its summer retreat. If so, it is the “the lowest and one of the earliest” on record. Of greater concern will be the size of the ice cap when it reaches its summer minimum. Past decades have seen a downward trend in both. NASA reports from its Global Climate Change website:
The sea ice cap of the Arctic appeared to reach its annual maximum winter extent on Feb. 25, according to data from the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado, Boulder. At 5.61 million square miles (14.54 million square kilometers), this year’s maximum extent was the smallest on the satellite record and also one of the earliest.
Arctic sea ice, frozen seawater floating on top of the Arctic Ocean and its neighboring seas, is in constant change: it grows in the fall and winter, reaching its annual maximum between late February and early April, and then it shrinks in the spring and summer until it hits its annual minimum extent in September. The past decades have seen a downward trend in Arctic sea ice extent during both the growing and melting season, though the decline is steeper in the latter.
This year’s maximum was reached 15 days earlier than the 1981 to 2010 average date of March 12, according to NSIDC. Only in 1996 did it occur earlier, on Feb. 24. However, the sun is just beginning to rise on the Arctic Ocean and a late spurt of ice growth is still possible, though unlikely.
If the maximum were to remain at 5.61 million square miles, it would be about 50,000 square miles below the previous lowest peak wintertime extent, reached in 2011 at 5.66 million square miles — in percentages, that’s less than a 1 percent difference between the two record low maximums. In comparison, the swings between record lows for the Arctic summertime minimum extent have been much wider: the lowest minimum extent on record, in 2012, was 1.31 million square miles, about 300,000 square miles, or 18.6 percent smaller than the previous record low one, which happened in 2007 and clocked at 1.61 million square miles.
A record low sea ice maximum extent does not necessarily lead to a record low summertime minimum extent.
“The winter maximum gives you a head start, but the minimum is so much more dependent on what happens in the summer that it seems to wash out anything that happens in the winter,” said Walt Meier, a sea ice scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “If the summer is cool, the melt rate will slow down. And the opposite is true, too: even if you start from a fairly high point, warm summer conditions make ice melt fast. This was highlighted by 2012, when we had one of the later maximums on record and extent was near-normal early in the melt season, but still the 2012 minimum was by far the lowest minimum we’ve seen.”