With thinner ice leading to faster melting, Arctic sea-ice coverage has reached a record low. On September 11, the National Snow and Ice Data Center in Colorado measured the extent of Arctic ice cover to be approximately 1.321 million square miles, a little more than half the extent measured in the 1980s and 1990s.
Sea surface temperatures continued to be high, compared to the average temperature between 1979 and 2000. In part the higher temperatures are caused by the loss of reflective ice cover. Solar radiation penetrates the dark, open-water areas exposed by ice melt and warms the mixed layer of the ocean.
Old, or multiyear, ice continues to decline. Because it is thicker, it is less prone to melting. By late summer the overall amount of old ice had declined by 33 percent, with the oldest ice, more than five years old, declining by 51 percent.
Loss of the ice cover is likely to cause major climatic shifts as a warmer polar region affects the Arctic Oscillation and the global weather patterns that it produces.