According to the National Oceanic and Atmospheric Administration, the polar vortex that affects people in the Northern Hemisphere is a fast belt of westerly winds, between about 10 and 30 miles high, that intensify every winter, enclosing a large pool of extremely cold air over the North Pole and central Arctic Ocean. (There is an even stronger polar vortex in the Southern Hemisphere stratosphere during its winter.) When the vortex wobbles or expands, the cold air spills southward, causing cold snaps in North America, Europe or Asia.
Most recently, a kink in the polar vortex probably played a role in the deadly February 2021 outbreak of cold weather in the Southern Plains that caused massive power outages in Texas. NOAA climate researcher Amy Butler wrote in a blog post that the polar vortex “got stretched out of shape and slid southward off the pole.”
Scientists can’t yet tell for certain if global warming will disrupt the polar vortex more frequently, but there are several plausible theories for how that might happen, including how shrinking sea ice affects the path of atmospheric waves that can shift the vortex if they are warm and high enough.