Long-term trend still sharply downward
By Summit Voice
FRISCO — The Boulder-based National Snow and Ice Data Center is reporting that Arctic sea ice appears to have reached its minimum extent Sept. 13.
At about 1.97 million square miles, the minimum extent this year was not as extreme as last year’s record low, but still registered as the sixth-lowest on record.
The long-term trend is still a steady decline. Much of the Arctic may be completely free of of sea ice within the next few decades, said NSIDC director Mark Serreze.
“The pattern we’ve seen so far is an overall downward trend in summer ice extent, punctuated by ups and downs due to natural variability in weather patterns and ocean conditions,” Serreze said.
Sea ice is frozen ocean water that melts each summer and refreezes each winter. The Arctic sea ice minimum marks the day — typically in September — when sea ice reaches its smallest extent.
The ice researchers said the data on this year’s minimum extent is not final. Changing winds could still push the ice extent lower.
NSIDC scientists said this year’s higher extent is a temporary reprieve for the sea ice. “While this is a very welcome recovery from last year’s record low, the overall trend is still decidedly downwards,” said NSIDC director Mark Serreze.
NSIDC research scientist Julienne Stroeve said this year’s summer was cooler than the last several summers and that helped to slow the melting.
“Despite the lower temperatures, ice extent still fell well below the long-term average. That’s consistent with the Arctic’s ice cover being thinner than it was a few decades ago,” Stroeve said.
Arctic sea ice has long been recognized as a sensitive climate indicator. The region’s sea ice extent—defined by NSIDC as the total area covered by at least 15 percent of ice—has shown a large overall decline since the beginning of the satellite record in 1979.
“No single year’s turnaround can erase that,” said NSIDC lead scientist Ted Scambos. “Let’s not lose sight of the fact that 2013 is a very low extent year, despite the increase from last September.”
See an animation of this summer’s sea ice extent produced by NASA Scientific Visualization Studio at http://svs.gsfc.nasa.gov/goto?4104.