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It might seem counterintuitive to link Arctic sea ice that disappears in the summer to a colder winter in the northeastern U.S. and Europe, but scientists have reason to believe the connection is real and will make itself felt this upcoming season.
Less sea ice in summer means the Arctic Ocean warms more. It radiates much of that excess heat back to the atmosphere in winter. That release disrupts typical atmospheric conditions, thereby affecting how the jet stream behaves. The net result is a greater chance for unusually cold winters, or at times unusually warm ones, in the northeastern U.S. and Europe, according to an article by Cornell University Earth and atmospheric scientist Charles Greene in Scientific American’s December 2012 issue.
Each winter ice builds up across the Arctic Ocean. Each summer some of it melts or breaks off and is carried away by ocean currents. The ice cover reaches its minimum each September, then begins to build up again. The minimum amount of ice cover each summer had fluctuated above and below six million square kilometers from 1979 through 2000. Losses began to get greater each summer thereafter, apparently due to global warming, dropping to about five million square kilometers in 2007. Since that year the minimum ice cover has declined rapidly, dwindling to an all-time record low of 3.4 million square kilometers on September 16, 2012.
The graph below shows how much area the ice covered when it was at its summer minimum, for each year from 1979 to 2012. The animation of satellite data shows the physical extent of the ice cover for each of those minimum dates, ending with the record low. Both the graph and animation were produced by the NASA Goddard Space Flight Center.