Arctic Sea Ice Reaches 3rd Lowest Minimum Extent

On September 12, the extent of sea ice in the Arctic reached the third lowest level ever recorded since satellite records began in 1979. Only 2007 and 2008 have had smaller ice extents than 2009. Sea ice extent in 2009 is shown in light blue, while 2007 and 2008 are shown in red and purple, respectively. The small increase in ice extent seen in 2009 was mostly due to strong polar winds pushing the ice and causing it to spread. Ice concentration and thickness, however, did not increase, so scientists do not expect the sea ice extent to continue to increase like it has over the past three years.

Sea ice reflects sunlight, which keeps the Arctic region cool and plays a major role in moderating global climate. The lowest amount of ice cover occurs each year typically around September 15, after sea ice has melted through the warm summer months and before it begins to refreeze in the winter. While Arctic sea ice extent varies from year to year, overall it has declined dramatically over the past few decades. The National Snow and Ice Data Center estimates that the overall extent of Arctic sea ice in 2009 dropped to 5.1 million square kilometers, well below the average minimum extent of 6.71 million square kilometers measured from 1979-2000.

Images adapted from an animation courtesy of the NOAA Environmental Visualization Laboratory