Sea ice extent in the Arctic Ocean this year reached the second lowest level on record, according to the National Snow and Ice Data Center (NSIDC). NSIDC announced on Thursday that sea ice cover for the year apparently reached its minimum extent on September 9, following which it began to rebound with the onset of fall. That minimum extent, 4.33 million square kilometers (1.67 million square miles), was the second-lowest on record, 160,000 square kilometers (61,800 square miles) above the record minimum, in 2007.
NSIDC offers the caveat that changing wind patterns, or a late season melt, could yet cause the extent to diminish more. They also note that their initial calculations have an estimated uncertainty of plus or minus 50,000 square kilometers (about 20,000 square miles), and that some research institutions – for example, the University of Bremen – have calculated the total extent to be lower than 2007 levels. Total sea ice area – i.e. the total surface area of sea ice if it were all clumped together, as opposed to the total of the Arctic Ocean that it occupies – has also been calculated to have reached an historic low in 2011.
Additionally, the sea ice that remains is older and thinner. The Polar Science Center of the University of Washington announced last week that the total volume of Arctic sea ice in 2011 reached its lowest ever this year, the second year in a row that it has done so. UW researchers calculated that August sea ice volume was fully 62 percent below the 1979-2010 average.
IMAGE: Arctic Sea Ice Extent. (NSIDC)