In the Arctic, sea ice extent fluctuates with the seasons. It reaches its peak extent in March, near the end of Northern Hemisphere winter, and its minimum extent in September, at the end of the summer thaw. In September 2007, Arctic sea ice extent was the smallest area on record since satellites began collecting measurements about 30 years ago.
Since satellites began monitoring sea ice in 1979, researchers have observed a decline in the average extent of Arctic sea ice in every month of the year.
The extent of Arctic sea ice peaked at 15.24 million square kilometers on March 18, 2012. It was the ninth consecutive year of maximum extents below the long-term average.