End-of-Summer Arctic Sea Ice Extent Is Eighth Lowest on Record

Arctic sea ice appeared to have reached its yearly lowest extent on Sept. 13, NASA and the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder have reported. Analysis of satellite data by NSIDC and NASA showed that at 1.79 million square miles (4.64 million square kilometers), this year's Arctic sea ice minimum extent is the eighth lowest in the consistent long-term satellite record, which began in 1978.

Arctic sea ice, the layer of frozen seawater covering much of the Arctic Ocean and neighboring seas, is often referred to as the planet's air conditioner: its white surface bounces solar energy back to space, cooling the globe.  The sea ice cap changes with the season, growing in the autumn and winter and shrinking in the spring and summer.  Its minimum summertime extent, which typically occurs in September, has been decreasing, overall, at a rapid pace since the late 1970s due to warming temperatures.

This year, temperatures in the Arctic have been relatively mild for such high latitudes, even cooler than average in some regions.  Still, the 2017 minimum sea ice extent is 610,000 square miles (1.58 million square kilometers) below the 1981-2010 average minimum extent.

"How much ice is left at the end of summer in any given year depends on both the state of the ice cover earlier in the year and the weather conditions affecting the ice," said Claire Parkinson, senior climate scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland.  The weather conditions have not been particularly noteworthy this summer.  The fact that we still ended up with low sea ice extents is because the baseline ice conditions today are worse than the baseline 38 years ago."

The three years with the lowest Arctic ice extents on record -- 2012, 2016 and 2007 -- experienced strong summer storms that hammered the ice cover and sped up its melt.  "In all of those cases, the weather conditions contributed to the reduced ice coverage.  But if the exact same weather system had occurred three decades ago, it is very unlikely that it would have caused as much damage to the sea ice cover, because back then the ice was thicker and it more completely covered the region, hence making it more able to withstand storms," Parkinson said.

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