The Arctic ice sheet reached a record low minimum extent this season according to The National Snow & Ice Data Center. The ice sheet shrunk to about 3.4 Million kilometers, which is roughly HALF of the long term average minimum extent. Below is the extent of the Arctic ice sheet as measured by satellites for a 5 day average ending September 18th.
The white area represents actual ice cover and the orange line represents the long term average extent. The long term average minimum extent is around 6.7 million square km and the previous record minimum ice extent is around 4.1 million square km set in 2007. The graph below compares 2012 ice extent to the average and to 2007.
The minimum Arctic ice extent is typically set in mid September, when conditions become cold enough that refreezing begins. This new record is part of a longer term trend of less Summer ice extent.
The 5 years with the smallest minimum ice extent have all occurred since 2007. Note that the 2012 minimum ice extent is well below any of the other years, falling below 4 million square km for the first time since measurements began. Satellite measurements have been used to estimate ice extent since 1979.
It is important to note that loss of ice extent has NOT been observed in the Antarctic. As a matter of fact, ice coverage there has actually increased somewhat as a whole.
The blue line represents Arctic ice extent, while Antarctic ice coverage is represented in red.
According to scientists at the National Snow and Ice Data Center, climate models have shown the Arctic becoming completely free of ice during the Summer by 2050, however the observed rate of ice decline is actually much faster than what the models suggest. This suggests that Summer Arctic ice may disappear within the next decade. Such a drastic change in ice extent will very like have significant climate impacts for much of North America. It is not known, however, specifically what those impacts would be.