File:2008 Arctic Sea Ice Minimum w overlay 1280x720 (3086477806).jpg

Courtesy NASA Goddard Space Flight Center / Scientific Visualization Studio

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The continued significant reduction in the extent of the summer sea ice cover is a dramatic illustration of the pronounced impact increased global temperatures are having on the Arctic regions. There has also been a significant reduction in the relative amount of older, thicker ice. Satellite-based passive microwave images of the sea ice cover have provided a reliable tool for continuously monitoring changes in the extent of the Arctic ice cover since 1979. During 2008 the summer minimum ice extent, observed in September, reached 4.7 million km2. While slightly above the record minimum of 4.3 million km2, set just a year earlier in September 2007, the 2008 summer minimum further reinforces the strong negative trend in summertime ice extent observed over the past thirty years. At the record minimum in 2007, extent of the sea ice cover was 39% below the long-term average from 1979 to 2000. A longer time series of sea ice extent, derived primarily from operational sea ice charts produced by national ice centers, suggests that the 2007 September ice extent was 50% lower than conditions in the 1950s to the 1970s (Stroeve et al. 2008). The spatial pattern of the 2008 minimum extent was different than in 2007. The annual maximum sea ice extent typically occurs in March. In March 2008, the maximum ice extent was 15.2 million km2. This marked a second year of slight recovery in winter ice extent from the record minimum of 14.4 million km2 for the period 1979–2008, which was observed in 2006. For comparison, the mean monthly ice extent for March and September, for the period 1979–2008, is 15.6 and 6.7 million km2, respectively.