The extent of sea ice this September is substantially greater than last year’s record low. On September 16, 2012, Arctic sea ice spread across just 3.41 million square kilometers (1.32 million square miles)—the smallest extent ever recorded by satellites and about half the average minimum from 1981 to 2010.
Though less Arctic sea ice melted in 2013 compared to 2012, this year’s total is the sixth lowest in the satellite record. This year continues a long-term downward trend of about 12 percent Arctic sea ice loss per decade since the late 1970s—a decline that accelerated after 2007.
“I was expecting that this year would be higher than last year,” said Walt Meier, a glaciologist at NASA’s Goddard Space Flight Center. “There is always a tendency to have an uptick after an extreme low. In our satellite data, the Arctic sea ice has never set record low minimums in consecutive years.”
The map above shows the extent of Arctic sea ice on September 13, 2013. Extent is defined as the total area in which the ice concentration is at least 15 percent. The map was compiled from observations by the Advanced Microwave Scanning Radiometer 2 (AMSR-2) sensor on the Global Change Observation Mission 1st–Water (“Shizuku”) satellite, which is operated by the Japan Aerospace Exploration Agency (JAXA). The yellow outline on the map shows the median sea ice extent observed in September from 1981 through 2010.
In summer 2013 (June, July, August), the average extent was 8.71 million square kilometers, compared to 7.85 million in 2012 (the record low for the summer months), and 10.40 million in 1979, the first full year of satellite measurements. These sea ice data are archived and distributed by NSIDC.
The ice cap covering the Arctic Ocean shrinks and expands with the seasons. It grows dramatically each winter, usually reaching its maximum in March. It melts just as dramatically each summer, generally reaching its minimum in September. The plot below shows this annual cycle, including the long term trends and the past two years.
- NASA Earth Observatory World of Change: Arctic Sea Ice.
- National Snow and Ice Data Center (2013, September 20) Arctic sea ice reaches lowest extent for 2013. Accessed September 20, 2013.
- GCOM-W1 - AMSR-2
NASA: North Pole - 2013 Arctic Sea Ice Minimum - 09.28.13
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