Arctic Sea Ice Extent Reaches Annual Minimum, Among Lowest On Record

Arctic sea ice on 3 September 2010, shortly before the ice reached its annual minimum extent on 10 September.  NASA's Aqua satellite used microwaves to capture the snapshot.  Source: NASA Earth Observatory.

Arctic sea ice on 3 September 2010, shortly before the ice reached its annual minimum extent on 10 September.  NASA's Aqua satellite used microwaves to capture the snapshot.  Source: NASA Earth Observatory.

The U.S. National Snow and Ice Data Center (NSIDC) reports today (15 Sep 2010) that Arctic Sea Ice appears to have reached its annual minimum extent on Friday, 10 September.  The area of sea ice has increased since then (over the subsequent four days).  "The minimum ice extent was the third-lowest in the satellite record, after 2007 and 2008, and continues the trend of decreasing summer sea ice," says the NSIDC.

Arctic Sea Ice Extent, 2010 through 13 September; and compared to 1979-2000 average and previous select years.  Source: NSIDC.

Above: Arctic sea ice extent, 2010 (through 13 September) compared to 1979-2000 average and previous select years.  Source: NSIDC.

In Arctic sea ice reaches annual minimum extent , the NSIDC says:

"The 2010 minimum is 1.95 million square kilometers (753,000 square miles) below the 1979 to 2000 average minimum and 1.62 million square kilometers (625,000 square miles) below the thirty-one-year 1979 to 2009 average minimum....This is only the third time in the satellite record that ice extent has fallen below 5 million square kilometers (1.93 million square miles), and all those occurrences have been within the past four years."

Sea Ice Extent on 10 September 2010 compared to median extent (1979-2000).  Source: NSIDC.

Above: Sea Ice Extent on 10 September 2010 compared to median extent (1979-2000).  Source: NSIDC.

In early October, the NSIDC will issue a detailed sea ice overview for the month of September, including the monthly average September sea ice extent -- "the measure scientists rely on for accurate analysis and comparison over the long term." It also will issue "a full analysis of the melt season, and graphics comparing this year to the long-term record."

In Exclusive: Scientists track sharp drop in oldest, thickest Arctic sea ice, Joe Romm at Climate Progress highlights the importance of sea ice volume (as opposed to simply sea ice extent).  The thickest multi-year ice is declining in the Arctic as thinner, new (first year) ice becomes more prevalent. As the volume of sea ice declines, it is more vulnerable to melting away entirely during the melt season (roughly March to September). 

Romm argues that the low extent of sea ice combined with the thinning of the ice may have reduced sea ice volume in the Arctic to a record low.  "[A]lthough it may be a while before we have a definitive statement, the likelihood seems high that we just set the record low Arctic sea ice volume — possibly for several thousand years (see Major analysis finds “less ice covers the Arctic today than at any time in recent geologic history”)."

Record or not, in the end all that matters to walruses hauled out along the Alaska coastline of the Chukchi sea is the fact that there presently is no ice in sight.

Online Resources:

Video: 2010 Arctic Sea Ice Update (13 Sep 2010).  As Arctic sea ice reaches its annual minimum extent --  the third lowest on record -- and as tens of thousands of Walruses are hauled-out along the Chukchi shoreline in Alaska, Peter Sinclair provides us with an invaluable -- and sometimes humorous -- video update on the state of Arctic sea ice.

Arctic Sea Ice Decline and its Impacts: Online Resources .  Updated regularly.

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