What is behind the “Arctic explosion” hitting the United States?

What is behind the “Arctic explosion” hitting the United States?

A climate scientist says this week’s cold snap in the US will be one of the “most impressive Arctic outbreaks this century.”

After months of record-breaking warm temperatures, much of the United States is facing a harsh, fast-moving blast of frigid air from the Arctic that could drop wind chill factors below zero degrees Fahrenheit (-18 degrees Celsius) — all Close on its heels is a dangerous winter storm dumping snow over the Midwest and Great Lakes this weekend.

“It would be very impressive, certainly one of the most impressive Arctic outbreaks this century anyway,” says Judah Cohen, a climate scientist at the atmospheric and environmental research firm Verisk. Cohen notes that similar recent events included a terrible cold snap that hit Texas in February 2021 and a severe pre-holiday freeze in December 2022.

Fortunately, this Arctic blast is not expected to be as deadly as the Texas event, which knocked out power for four million people, says Christina Dahl, a climate scientist at the Union of Concerned Scientists, who adds that updates in recent years should… Reduces the stress that cold air puts on the power grid during this event.

To understand how this arctic blast could affect you and what risks to prepare for, consult your local National Weather Service office. Meanwhile, here’s the science behind why temperatures have suddenly dropped so sharply across such a wide swath of North America.

Normally, very cold air in the Arctic is trapped within a vortex of high-altitude winds called the polar vortex, which is surrounded by a low-altitude band called the polar jet stream. However, if the polar vortex is disrupted, the jet stream could become wavy and carry cold air farther south than usual in an Arctic blast. Sometimes this cold air brings snow and ice. Other times the weather is dry but very cold.

Scientists are still trying to accurately determine the causes of these disorders. “It’s a very active area of ​​research, and it’s something that scientists are enthusiastically discussing and trying to figure out right now,” says Dahl. “It’s definitely not settled science.”

However, many experts believe that climate change is likely to play a role, and Cohen goes further: He asserts that climate change in the Arctic is directly disrupting the polar vortex. According to Cohen, this winter’s melting sea ice near Scandinavia combined with heavy snowfall near Siberia has created thermal anisotropy, which he says has pushed the polar jet stream into waves. He adds that the polar vortex typically “wake up” around January, so it stands to reason that we are now feeling the intense cold caused by the Arctic blast whose stage was set by these distant trends.

“It seems counterintuitive and surprising that a warmer planet could actually increase your odds of experiencing extreme winter weather events — but that’s what our research has shown,” Cohen says.

Cohen adds that he expects a second, less dangerous explosion to occur in the Arctic later this month, and that this phenomenon is likely to be repeated in February as well.

Although science is still working to refine an explanation for the polar vortex disturbances and the accompanying explosions in the Arctic, Dahl believes that the irony of this incident coincides with the US government’s assertion that 2023 was the hottest year on record. “To me, this is an indicator of global climate change with greater extremes,” she says.

“I like to think of the polar jet stream outbreak as a ‘global freak,’” Dahl adds. “Climate change is causing all kinds of different impacts, some of which are counterintuitive.”

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