Arctic Ice Cover Headed for All-time Record Low

June marks the beginning of the melt season for Arctic sea ice, which reaches its minimum extent at the end of the season in September. In the past few Septembers, Arctic sea ice concentration (the amount of ice in a given area) has been markedly reduced. September 2002 set a new record low at 15 percent below average. It was followed closely by September 2003 and September 2004. So far, 2005 is shaping up to be another record-low sea ice year in the Arctic...

Different explanations have been proposed for Arctic sea ice decline, including the strong positive mode of the Arctic Oscillation (AO). This oscillation is an alternating pattern of atmospheric pressure at polar latitudes and mid-latitudes. In the early 1990s, the AO was in positive mode. In that mode, the AO produces a strong polar vortex, and resulting winds tended to flush older, thicker ice out of the Arctic. Since the late 1990s, however, the AO has been much more neutral, yet Arctic sea ice decline continues. Another explanation for declining sea ice is climate change. Global temperatures have risen, and climate models generally agree that one of the strongest signals of greenhouse warming is a loss of Arctic sea ice.

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