The following text was sent to me by Al Rodger:
Four years ago, the year 2007 saw the record-breaking summer/autumn melt season in the Arctic. As the Extent of sea ice during the preceding winter maximum was also low, 2007 easily set the record for 12 month rolling average for Arctic Sea Ice Extent. Four years later, that annual record has now been broken.
Using the figures from NSIDC, the 12 month rolling average for Arctic Sea Ice Extent dropped from last month's 10.67 million sq km to 10.62 this month, setting the new record. Previously the record had been set by the-year-to-October 2007 with an Extent of 10.66, the record standing for 48 months.
The record for Arctic Sea Ice Area has also been broken. The-year-to-October 2007 was again the previous record, standing at 8.39 million sq km. Annual average Sea Ice Area dropped to 8.34 for the-year-to-October 2011.
Using different satellite data & analysis, the JAXA Sea Ice Extent record was set at 9.946 million sq km in the-year-to-December 2007. By 3 October 2011, when the AMSR-E satellite data ceased, JAXA's rolling 365 day average stood at 10.005. At the rate that the average had been decreasing, JAXA's monthly averages would have broken the record this year-to-November, or after 47 months.
By comparison, Sea Ice Volumes have been decreasing far more quickly. The '2007' record value modelled by PIOMAS calculated to 15,075 cu km, set in the-year-to-January 2008. It was broken in just 29 months. The-year-to-September 2011 average has been calculated at 13,140 cu km.
The record breaking 2007 season is the largest 'blip' in the satellite record of Arctic Sea Ice Extent but there are other such 'blips'. The second largest 'blip' occurred in 1995/6 when the 1995 summer/autumn minimum extent stood as a record for seven years and the following 1996 winter/spring maximum extent was also a record low for eight years. The resulting 12 month rolling NSIDC Extent record was set at 11.72 million sq km in the-year-to-April 1996. It was bested for one month (the-year-to-September 2002) by a mere 7,500 sq km, such a small margin it probably counts as a draw rather than a new record.
It took to January 2004 before 1996's 12 month rolling average Extent record was convincingly broken, the 1996 record thus standing for 93 months. That records from the larger 2007 'blip' tumbled in nearly half the time is indicative of the accelerating decline in Arctic Sea Ice.