by Staff Writers
Potsdam, Germany (SPX) Sep 25, 2017
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."
Warm Arctic, cold continents
Weak states of the high-altitude wind circling the Arctic then favors the occurrence of cold spells in the mid-latitudes. Previous work by Kretschmer and colleagues identified this causal pathway in observational data and it is further supported by several climate computer simulation studies.
"Our latest findings not only confirm the link between a weak polar vortex and severe winter weather, but also calculated how much of the observed cooling in regions like Russia and Scandinavia is linked to the weakening vortex. It turns out to be most," says co-author Judah Cohen from Atmospheric and Environmental Research/Massachusetts Institute of Technology (US).
"Several types of weather extremes are on the rise with climate change, and our study adds evidence that this can also include cold spells, which is an unpleasant surprise for these regions." The effect is stronger over Asia and Europe than over the US.
Circulation patterns drive our weather"
Greenbelt MD (SPX) Sep 21, 2017
Arctic sea ice appeared to have reached its yearly lowest extent on Sept. 13, NASA and the NASA-supported National Snow and Ice Data Center (NSIDC) at the University of Colorado Boulder have reported. Analysis of satellite data by NSIDC and NASA showed that at 1.79 million square miles (4.64 million square kilometers), this year's Arctic sea ice minimum extent is the eighth lowest in the consist ... read more
Potsdam Institute for Climate Impact Research (PIK)
Beyond the Ice Age
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