Though global temperatures are warming, winters in the Northern Hemisphere are still marked by cold snaps and extreme snowfall events — sometimes to an unprecedented extent, such as the 2021 deep freeze in Texas and Oklahoma that caused over $1 billion in damage.
Now, a new study suggests that these cold extremes are due to an increasingly common pattern in the polar vortex, the zone of low pressure that usually circulates over the Arctic. Disruptions to this vortex cause it to deform and stretch, spewing cold air into Canada and the U.S. These disruptions are becoming more common as the Arctic warms.
“Overwhelmingly, extreme cold and severe winter weather, heavy snowstorms and deep snow, are associated with these stretched events,” study co-author Judah Cohen, the director of seasonal forecasting at Atmospheric and Environmental Research and a visiting scientist at MIT, told Live Science.
Cohen and his team looked at how these events evolve in the stratosphere, the middle layer of the atmosphere that starts about 12 miles (19 kilometers) up. Understanding how these patterns shift could help meteorologists make longer-range forecasts, said Andrea Lopez Lang, an atmospheric scientist at the University of Wisconsin—Madison who was not involved in the research.
“Knowing this information is useful for a lot of applications in energy [and] applications in insurance or reinsurance,” Lang told Live Science. “How cold is it going to get? Are pipes going to burst? Are insurance claims going to spike this winter?”
Usually, the polar vortex circulates around the North Pole like a spinning top. Occasionally, it collapses dramatically, which usually leads to polar air rushing toward northern Europe and Asia. These collapses can sometimes cause cold snaps in North America — but not always.
“There’s been this big question mark over what happens in North America,” Lang said.
Related: US suffers record-breaking cold: What’s going on with the polar vortex?
Cohen and his colleagues looked at stratosphere data from satellite observations between 1980 and 2021, as well as winter weather records from the same period. They found that, short of total collapse, the polar vortex often wobbles and stretches, like a figure skater…
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