Arctic Sea Ice in July is Second Lowest on Record, Maintaining Rapid Longer Term Decline

The National Snow and Ice Data Center (NSIDC) reported on 4 August 2010 that the extent of Arctic Sea Ice has dropped to the second lowest level on record, second only to 2007.  Over the 1979-2010 period, the extent of Arctic sea ice has declined at an average rate of 6.4% per decade.  See figure below.

Average July Arctic Sea Ice Extent, 1979-2010.  Source: National Snow and Ice Data Center.

Above: Average July Arctic Sea Ice Extent, 1979-2010.  Source: National Snow and Ice Data Center.

The NSIDC says that the average ice extent during July was 8.39 million square kilometers (km2) (3.24 million square miles), 1.71 million km2(660,000 square miles) below the 1979 to 2000 mean. 


As the figure below indicates, the extent of Arctic sea ice follows a seasonal pattern, typically reaching a maximum in March and then declining into September when it usually reaches an annual minimum.  The record low sea ice minimum was reached in September 2007.  It is not clear whether the minimum will reach record levels this year.  What is clear -- and important -- is that sea ice extent will drop to very low levels by the minimum in September, and this is consistent with a long-term trend of declining sea ice. 


Sea Ice Extent, 2002-2010.  Source: IARC-JAXA.

Above: Sea Ice Extent, 2002-2010 (through 4 August 2010).  Click on image for larger version.  Sea ice extent for 2010 (in red) now is lower than at any other time except the record low year of 2007.  Source: International Arctic Research Center (IARC) and Japan Aerospace Exploration Agency (JAXA) Information System (IJIS).

What's more, the NSIDC notes that some of the ice that now is melting out is thicker ice that has been around for years.  This ice, also called multi-year ice, has been declining in the Arctic and is being replaced with first year ice that is thinner and more easily melted each year. Stated differently, the volume of sea ice is declining along with the extent of sea ice.

The NSIDC announced the July data the day before a massive ice island broke off the Petermann Glacier in Greenland on 5 August. See our posting Greenland Glacier Calves the Arctic's Largest Ice Chunk in Nearly a Half-Century (8 August 2010).

Online Resources

July sea ice second lowest: oldest ice begins to melt.  National Snow and Ice Data Center, 4 August 2010. 

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