September 16, 2011
Arctic Sea Ice At Second-lowest Level Since 1979
The extent of Arctic Ocean sea ice fell to its second-lowest size since 1979, the U.S. National Snow and Ice Data Center (NSIDC) said on Thursday.
According to preliminary findings, the annual sea ice minimum was reached on September 9, when the ice covered 1.67 million square miles, the center said in a statement.
"Changing winds could still push ice flows together reducing ice extend further," the researchers said.
A full analysis will be available early next month, when data is available for the entire month of September, the month when the annual sea ice extent minimum is typically reached before cold weather makes it expand again.
This year's minimum is more than 1 million square miles -- an area larger than Texas and California combined -- below the 1979-2000 monthly average extent for September, the center said.
And 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, said researchers involved in the analysis.
"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."
In 2007, there was a "nearly perfect" set-up of specific weather conditions, Serreze explained. 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.
The last five years have been the five lowest Arctic sea ice extents recorded since satellite measurements began in 1979, said CU-Boulder's Walt Meier, an NSIDC scientist.
"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."
CU-Boulder's NSIDC said it will issue a full analysis of the 2011 results, along with a comparison to previous years, during the first week of October.
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