Downward slide for arctic sea ice

U. COLORADO-BOULDER (US) — 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.

The Arctic sea ice extent fell to 1.67 million square miles, or 4.33 million square kilometers on Sept. 9, 2011—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.


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. (Credit: University of Colorado National Snow and Ice Data Center.)

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,” says Mark Serreze, professor of geography at the University of Colorado-Boulder and director of its National Snow and Ice Data Center.

“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.”

In 2007, the year of record low Arctic sea ice, there was a “nearly perfect” set-up of specific weather conditions, Serreze says.  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.”

The last five years have been the five lowest Arctic sea ice extents recorded since satellite measurements began in 1979, says NSIDC  scientist Walt Meier.

“The primary driver of these low sea ice conditions is rising temperatures in the Arctic, and we definitely are heading in the direction of ice-free summers. Our best estimates now indicate that may occur by about 2030 or 2040.”

SIDC is part of CU-Boulder’s Cooperative Institute for Research in Environmental Sciences— a joint institute of CU-Boulder and the National Oceanic and Atmospheric Administration headquartered on the CU campus— and is funded primarily by NASA.

NSIDC’s sea ice data come from the Special Sensor Microwave Imager/Sounder sensor on the Defense Meteorological Satellite Program F17 satellite using methods developed at NASA’s Goddard Space Flight Center in Greenbelt, Md.

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