Weakening of winter polar vortex linked to extremes in cold in parts of the Northern Hemisphere
September 27, 2017; 12:51 PM
A new study from the Potsdam Institute for Climate Impact Research has found that there has been a shift toward more-persistent weak states of the polar vortex over the past four decades.
When the polar vortex weakens, strong winds that normally circle the Arctic slacken, which can allow cold, polar air to escape southward, resulting in extreme bouts of winter cold in parts of the Northern Hemisphere.
This study 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.
The steady decline of sea ice in the far north over the past few decades may be the main culprit. When sea ice north of Scandinavia and Russia melts, the uncovered ocean releases more warmth into the atmosphere and this can impact the atmosphere up to about 30 kilometers height in the stratosphere, disturbing (weakening) the polar vortex, according to PIK Potsdam.
Key quote from the PIK article........
"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 United States.
This study was recently published in the Bulletin of the American Meteorological Society.
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