As sea ice melts, Arctic storms intensify

The extent of Arctic sea ice at the end of October was the second lowest since reliable record-keeping began in 1979. According to the National Snow and Ice Data Center, strong warm winds from the south slowed the seasonal growth in sea ice during the month.

Only October of 2007 saw a lower expanse of Arctic sea ice. For the year overall, the NSIDC has reported that Arctic sea ice reached its third lowest extent since 1979 in September, exceeded only in 2007 and 2008.

“At the end of the month, extensive areas of open water regions were still present in the northernmost North Atlantic, and north of Alaska,” the NSIDC reported. The extensive open water in combination with the warm winds led to a mean monthly temperature as high as 6 degrees Celsius (11 degrees Fahrenheit) above average in an extensive region of the Arctic Ocean.

Daily sea ice extent as of Nov. 1, 2009. The solid gray line shows the average extent from 1979 to 2000. The gray area around the average line shows the two standard deviation range of the data.

Sea ice actually is an excellent insulator separating the relatively warm ocean from the cold atmosphere. Without it, copious amounts of heat can flow into the atmosphere unimpeded. “With sea ice separating the ocean and atmosphere, they are prevented from talking to each other,” Mark Serreze, director of the NSIDC, said during a recent seminar here at the University of Colorado. “By losing the sea ice, we’re starting to open that window and pump ocean heat into the atmosphere, making it warmer.”

Because the sun does not shine in the Arctic for half the year, it is “the refrigerator of the Northern Hemisphere,” Serreze said. Sea ice contributes strongly to this phenomenon, not only by insulating the warmer ocean from the colder atmosphere but also by reflecting a singificant percentage of the Sun’s energy back into space. With the steady decline in sea ice, the refrigerator isn’t working as well as it once did. And this can have impacts beyond the Arctic.

“If you lose that ice you will have an effect on weather patterns that extend beyond Arctic,” he said. “You will change energy budget in Arctic, and what happens up there influences things down here.”

According to today’s NSIDC report, a new study by researchers at the University of Melbourne in Australia, has found that as ice extent has decreased, Arctic storms have tended to become more intense. When September ice extent is low, extensive areas of open water allow more energy to be fed to autumn storms, helping intensify them. These stronger storms, in turn, help break up the ice. “Related research at NSIDC reveals that when September ice extent is unusually low, precipitation linked to Arctic storms tends to be greater than when September ice extent is unusually high,” the report stated.