Arctic Sea Ice Hits Second-Lowest Level

Hydro International - 

In September 2011 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, USA, 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. NSIDC scientist Walt Meier said that atmospheric and oceanic conditions were not as conducive to ice loss this year, but the melt still neared 2007 levels, probably reflecting loss of multiyear ice in the Beaufort and Chukchi seas as well as other factors that are making the ice more vulnerable.

Joey Comiso, senior scientist at NASA's Goddard Space Flight Center in Greenbelt, MD, said the continued low minimum sea ice levels fits into the large-scale decline pattern that scientists have watched unfold over the past three decades.

While the sea ice extent did not dip below the 2007 record, the sea ice area as measured by the microwave radiometer on NASA's Aqua satellite did drop slightly lower than 2007 levels for about 10 days in early September, Comiso said. Sea ice area differs from extent in that it equals the actual surface area covered by ice, while extent includes any area where ice covers at least 15 percent of the ocean.

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