Last month the extent of sea ice covering the Arctic Ocean declined to the second-lowest extent on record. Satellite data from NASA and the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado in Boulder showed that the summertime sea ice cover narrowly avoided a new record low.The Arctic ice cap grows each winter as the sun sets for several months and shrinks each summer as the sun rises higher in the northern sky. Each year the Arctic sea ice reaches its annual minimum extent in September. It hit a record low in 2007.The near-record ice-melt followed higher-than-average summer temperatures, but without the unusual weather conditions that contributed to the extreme melt of 2007. "Atmospheric and oceanic conditions were not as conducive to ice loss this year, but the melt still neared 2007 levels," said NSIDC scientist Walt Meier. "This probably reflects loss of multiyear ice in the Beaufort and Chukchi seas as well as other factors that are making the ice more vulnerable."
This video shows Arctic sea ice from March 7, 2011, to Sept. 9, 2011, ending with a comparison of the 30-year average minimum extent (in yellow) and the Northwest Passage (shown in red). (Credit: NASA's Goddard Space Flight Center)
Arctic sea ice continues a long-term melting trend, setting new record lows for both volume and extent.The University of Washington (UW) estimatesAugust sea ice volume was 62% below the 1979-2010 average. And data indicate the volume bottomed out at a record low (as also documented on the excellent Arctic sea ice blog). The UW model for estimating sea volume incorporates data from satellites, Navy submarines, moorings, and field measurements as well as atmospheric information.
News of the “unofficial” 2011 record for minimum Arctic sea ice volume follows acceptance of an article in the Journal of Geophysical Research which demonstrates the 2010 minimum sea ice volume was lower than 2007, the previous record holder.
The sea ice volume metric is important because, unlike extent, it provides information on ice thickness and, thus, offers a more complete picture of what’s happening to the ice.
As for sea ice extent, the University of Bremen (in Germany) reports it reached a new historic minimum of 4.24 million square kilometers on September 8. In a press release it stated:
It seems to be clear that this is a further consequence of the man-made global warming with global consequences.
An alternative estimate from the National Snow and Ice Data Center (NSIDC) indicates that Arctic sea ice extent is currently at the second-lowest levels in the satellite record - very slightly higher than 2007.
http://www.washingtonpost.com/blogs/cap … _blog.html
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