Explainer: How Arctic Warming Pushes Much of North America Into a Deep Freeze

With eastern Canada and the eastern and midwestern United States in the midst of a brutal cold snap, meteorologists are expecting the polar vortex to occur more frequently. And they’re connecting the deep freeze to Arctic warming brought on by climate change.

“While climate change is warming the Earth, not all parts of the Earth are warming at the same rate; the Arctic is warming at a rate twice as fast as the world average,” the New York Times explains. “That warming has led to historically low levels of sea ice in the region. The melting sea ice, particularly in an area near the Barents and Kara Seas off Siberia, may be linked to the changes in the polar vortex.”

The polar vortex hit popular consciousness in 2014, but had been known to scientists for some time before that. “The term refers to circular bands of winds near the poles that are strongest in wintertime and well above the jet stream in the stratosphere,” the Times reports. “Usually, those circular bands act as walls that keep the teeth-chattering cold air locked at the poles. But, every so often, the winds break down and allow the cold air to escape. That’s what happened at the beginning of January, when the polar vortex split into three separate bands.”

Scientists “are still trying to figure out why these intense arctic chills are flooding southward more frequently,” the paper adds. But researchers like Jennifer Francis, senior scientist at the Woods Hole Research Center, and climatologist Judah Cohen at Atmospheric and Environmental Research, a private weather risk assessment firm, see a changing climate driving the trend.

“When we lose a lot of ice in that particular area in the summer, it absorbs a lot of extra heat from the sun,” Francis said. “And so we see a very persistent hot spot there in terms of temperature differences from what they should be.”

“As the Arctic gets warmer and warmer, the severe weather picks up,” Cohen added.

While the U.S. National Oceanic and Atmospheric Administration (NOAA) is predicting a milder winter overall, the Times notes that doesn’t rule out periods of extreme cold.

“There’s a difference between some seasonal outlooks such as NOAA’s that look at the whole three-month period and others that may be breaking it down month by month,” said meteorologist Bob Henson of Weather Underground. “It’s quite possible the winter will average warm for December through February. But that may well manifest as the extreme warmth we’ve seen over the last month followed by some much colder and colder than average conditions into February.”