University of Colorado at Boulder: The blanket of sea ice that floats on the Arctic Ocean appears to have reached its lowest extent for 2011, the second lowest recorded since satellites began measuring it in 1979, according to the University of Colorado Boulder's National Snow and Ice Data Center.The Arctic sea ice extent fell to 1.67 million square miles, or 4.33 million square kilometers on Sept. 9, 2011. This year's minimum of 1.67 million square miles is more than 1 million square miles below the 1979-2000 monthly average extent for September -- an area larger than Texas and California combined.
While this year's September minimum extent was greater than the all-time low in 2007, it remains significantly below the long-term average and well outside the range of natural climate variability, according to scientists involved in the analysis. Most scientists believe the shrinking Arctic sea ice is tied to warming temperatures caused by an increase in human-produced greenhouse gases pumped into Earth's atmosphere.
"Every summer that we see a very low ice extent in September sets us up for a similar situation the following year," said NSIDC Director Mark Serreze, also a professor in CU-Boulder's geography department. "The Arctic sea ice cover is so thin now compared to 30 years ago that it just can't take a hit anymore. This overall pattern of thinning ice in the Arctic in recent decades is really starting to catch up with us."
Serreze said that in 2007, the year of record low Arctic sea ice, there was a "nearly perfect" set-up of specific weather conditions. Winds pushed in more warm air over the Arctic than usual, helping to melt sea ice, and winds also pushed the floating ice chunks together into a smaller area. "It is interesting that this year, the second lowest sea ice extent ever recorded, that we didn't see that kind of weather pattern at all," he said...
Map of September 20, 2011 sea ice extent from the National Snow and Ice Data Center
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