When the strong winds that circle the Arctic slacken, cold polar air can escape and cause extreme winter chills in parts of the Northern hemisphere.
A new study finds that these weak states have become more persistent over the past four decades and can be linked to cold winters in Russia and Europe. It is the first to show that changes in winds high up in the stratosphere substantially contributed to the observed winter cooling trend in northern Eurasia. While it is still a subject of research how the Arctic under climate change impacts the rest of the world, this study lends further support that a changing Arctic impacts the weather across large swaths of the Northern Hemisphere population centers.
“In winter, the freezing Arctic air is normally ‘locked’ by strong circumpolar winds several tens of kilometers high in the atmosphere, known as the stratospheric polar vortex, so that the cold air is confined near the pole,” says Marlene Kretschmer from PIK, lead-author of the study to be published in the Bulletin of the American Meteorological Society. “We found that there’s a shift towards more-persistent weak states of the polar vortex. This allows frigid air to break out of the Arctic and threaten Russia and Europe with cold extremes. In fact this can explain most of the observed cooling of Eurasian winters since 1990.”
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