Study eyes impacts to North Atlantic Oscillation
The loss of Arctic sea ice may not lead directly to an increase in cold weather extremes in Europe, according to scientists who studied the links between Arctic changes and mid-latitude weather. In the study, scientists with the University of Exeter found that dwindling sea ice does affect the North Atlantic Oscillation (NAO) weather phenomenon, which affects winter weather conditions in Northern Europe, in places such as the UK, Scandinavia and the Baltic states.
Earlier research suggested that the decline of sea ice results in more negative phases of the NAO, which means more easterly winds that transport colder air from the northern Scandinavia and Siberia to the UK. Some scientists hypothesized that would mean more frequent cold winters, like the Big Chill in 2009-2010. But the new study suggests that the cooling of more easterly winds is offset by the widespread warming effect of sea ice loss. The study is published in leading science journal, Nature Communications.
“We know that the NAO is an important factor in controlling winter weather over Northern Europe,” said study leader Dr. Richard Screen. “The negative phase of the NAO is typically associated with colder winters. Because of this it has been reasonable to think that we would experience more severe winter weather if Arctic sea-ice loss intensifies the negative phase of the NAO.
“This research indicates that although sea-ice loss does intensify the negative NAO, bringing more days of cold easterly winds, it also causes those same winds to be warmer than they used to be. These two competing effects cancel each other out, meaning little change in the average temperature of European winters as a consequence of sea-ice loss.”
The NAO basically refers to the position large scale high and low pressure systems over the North Atlantic. It affects the position of the jet stream, which, in turn, affects the weather over Europe.
“Scientists are eager to understand the far-flung effects of Arctic sea-ice loss. On the one hand this study shows that sea-ice loss does influence European wind patterns. But on the other hand, Arctic sea-ice loss does not appear to be a cause of European temperature change, as some scientists have argued,” Screen said.