How Melting Arctic Sea Ice Caused $90 Billion Texas Freeze
A study led by Judah Cohen, director of seasonal forecasting at Atmospheric and Environmental Research, a part of risk analytics firm Verisk, is the first to find a connection between the Arctic warming and extreme winter weather events. The paper, published Thursday in Science, combines observational data over the past four decades with new climate models.
Researchers analyzed the role of the polar vortex, a low-pressure system near the North Pole that helps keep cold air trapped in the Arctic. When some other event weakens it or when it’s disrupted, cold spills down toward southern latitudes.
“Melting sea ice across northwestern Eurasia, coupled with increased snowfall in Siberia, leads to a strengthening of the temperature difference from west to east across the Eurasian continent,” Cohen said. “When that temperature difference increases, it leads to more disruptions in the polar vortex.”
The cold blast that swept out of Canada and moved deep into the U.S. South last February led to widespread power outages in Texas, with the chill damaging power suppliers in an area ill-prepared for freezing temperatures. During the worst of it, 157 million people lived under winter storm warnings or other weather advisories.
The origins of that event can be traced to the accelerated melting of sea ice in the Kara and Barents Seas, to the northwest of the Eurasian land mass, Cohen’s research said. Combined with an increase in snowfall in Siberia, that led to a greater temperature difference between the lateral halves of the continent. “Even though the Arctic is warming two or three times faster than the rest of the world, it’s not homogeneous,” Cohen said. “In Eurasia, we’re seeing an increase in temperature differences — not from south to north, but from west to east.”
These temperature differences energize an existing climatological pressure ridge over Eurasia, and that, in turn, disrupts the polar vortex. The ridge’s energy is sometimes absorbed by the polar vortex, but it can also bounce off and into North America. That’s what happened last February, Cohen said.
Using the same combination of observational data and scientific models used in the paper, researchers are hoping they’ll be able to forecast such events with greater lead time, he said. “People could have used more warning for the cold spell in Texas.”
While the finding represents a major step forward in predictability, knowing where the cold will land is still a challenge, Cohen said. “Generally it will be east of the Rocky Mountains, but where exactly is harder to predict.”
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