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Arctic sea ice maximum marks beginning of melt season

On March 18, 2012, Arctic sea ice extent reached its annual maximum extent, marking the beginning of the melt season for Northern Hemisphere sea ice. This year’s maximum extent was the ninth lowest in the satellite record.

Figure 1. Arctic sea ice extent on March 18 was 15.24 million square kilometers (5.88 million square miles). The orange line shows the 1979 to 2000 median extent for that day. The black cross indicates the geographic North Pole. Sea Ice Index data. About the data.

Credit: National Snow and Ice Data Center
High Resolution Image

Overview of conditions

On March 18, 2012 Arctic sea ice likely reached its maximum extent for the year, at 15.24 million square kilometers (5.88 million square miles). The maximum extent was 614,000 square kilometers (237,000 square miles) below the 1979 to 2000 average of 15.86 million square kilometers (6.12 million square miles). The maximum occurred this year 12 days later than the 1979 to 2000 average date of March 6.

This year’s maximum ice extent was the ninth lowest in the satellite record, slightly higher than the 2008 maximum (15.24 million square kilometers or 5.88 million square miles) Last year, 2011, was the lowest maximum on record, 14.64 million square kilometers (5.65 million square miles). Including this year, the nine years from 2004 to 2012 are the nine lowest maximums in the satellite record.

 

The graph above shows daily Arctic sea ice extent as of March 25, 2012, along with the ice extents for the previous four years. 2011-12 is shown in light blue, 2010-11 is in pink, 2009-10 in dark blue, 2008-09 is in purple, and 2006-2007, the year with the record low minimum, is dashed green. The gray area around the average line shows the two standard deviation range of the data. Sea Ice Index data.

Credit: National Snow and Ice Data Center
High Resolution Image

Conditions in context
As of March 23, ice extent has declined for five days. However, there is still a chance that the ice extent could expand again. Sea ice extent in February and March tends to be quite variable, because ice near the edge is thin and often quite dispersed. The thin ice is highly sensitive to weather, moving or melting quickly in response to changing winds and temperatures, and it often oscillates near the maximum extent for several days or weeks, as it has done this year.

Arctic sea ice extent is declining in winter as well as in summer months, although the decline is not as steep in the winter months. At the beginning of April, NSIDC scientists will release a full analysis of winter conditions, along with monthly data for March. For more information about the maximum extent and what it means, see the NSIDC Icelights post, the Arctic sea ice maximum.

 

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