Warming of the earth’s northern hemisphere could lead to a series of cold winters and it is all down to shrinking sea ice in the Barents Sea affecting air streams. Vladimir Petoukhov, the lead author of a recent study and a climate scientist at the Potsdam Institute for Climate Impact Research says that “These anomalies could triple the probability of cold winters in Europe and northern Asia, such as the recent severe winters like last year’s or the one of 2005-06”.
The researchers base their assumptions on an elaborate computer model of general circulation, ECHAM5 which focuses on the Barents-Kara Sea north of Norway and Russia where a drastic reduction of ice was observed in the cold European winter of 2005-06. The area of sea lacking ice cover transfers a lot of heat to the normally cold and windy arctic atmosphere. What the researchers did was to feed the computer with data, gradually reducing the sea ice cover in the eastern Arctic from 100 percent to 1 percent in order to analyse the relative sensitivity of wintertime atmospheric circulation.
Warming the air over the Barents-Kara Sea seems to bring cold winter winds to Europe. “This is not what one would expect,” Petoukhov says. “Whoever thinks that the shrinking of some far away sea-ice won’t bother them could be wrong. There are complex teleconnections in the climate system, and in the Barents-Kara Sea we might have discovered a powerful feedback mechanism.”
Other theories for recent cold winters such as sunspot activity or a weakening of the Gulf stream “tend to exaggerate the effects,” according to Petoukhov. For example during the cold winter of 2005-06 where temperatures were ten degrees below the normal in Siberia no anomalies in the north Atlantic oscillation were observed.