The National Snow and Ice Data Centre has just released the results of its latest analysis of Arctic sea ice. Surprise -- the prognosis is not good. The maximum extent of Arctic sea ice occurred early this year, and, at 5.61 million square miles, was the smallest in four decades.
The map above shows the Arctic sea ice extent at its peak this year on February 25th, with extent defined as the total area in which the ice concentration is at least 15 %. For comparison, the satellite image below was captured on March 14th, 1983. Comparison with 1983 gives scientists an idea of how conditions this year strayed from the long-term average of 5.96 million square miles for the 1979 -- 2000 period. (Note that the area inside the white circle is a data gap caused by how satellites fly close to, but not directly over, the north pole.)
According to NASA:
Arctic sea ice -- frozen seawater floating on top of the Arctic Ocean and its neighbouring seas -- is constantly changing. It grows in the fall and winter, reaching its maximum between late February and early April. It shrinks in the spring and summer until it reaches its minimum extent in September. The past three decades have seen a downward trend in sea ice extent during both the growing and melting season, though the decline has been steeper in the melting season.
This year's maximum was reached 15 days earlier than the 1981 to 2010 average date of March 12. Ice conditions have been below average everywhere except in the Labrador Sea and Davis Strait. A late spurt of ice growth is possible, but it is unlikely now that spring sunlight is arriving in the Arctic Circle.
If the maximum remains at 14.54 million square kilometers, it would be about 130,000 square kilometers below the previous lowest peak (set in 2011).
Areas that appear to have experienced the most significant ice loss include the Siberian coastline and the Bering Straight, between Alaska and Russia. If you really like geeking out over this stuff, NASA has created a handy comparison tool that allows you to scroll back and forth between the two sea ice images shown above and watch our planet's cryosphere change in a blink. [NASA Earth Observatory]