A polar vortex during global warming? How does that work? I researched NOAA, the National Weather Service and the Center for Science Education to find out. This is what I learned.
The northern hemisphere has two vortexes in the winter. The polar “jet stream” exists year-round as the wandering west-to-east stream of powerful winds seven miles above us that guides warm and cold fronts across the country as its looping pattern constantly changes. A much more northern polar “vortex” forms each winter about 30 miles above the earth, and is a tighter and more circular powerful windstream.
Both are created where polar high pressure cold air masses meet warmer temperate zone lower pressure air.
Where that happens, strong vortex winds develop because air flows from colder high pressures to warmer low pressures, to create a continuous circular cooling/warming swirl of air. Greater temperature differences between cold air and warm air makes faster, stronger winds, and smaller temperature differences create weaker and slower winds. The earth’s rotation underneath keeps these winds moving in a west-to-east continuous flow. The more southern jet stream is slower than the polar vortex because of smaller temperature differences creating it, so it flows in a changeable meandering pattern, similar to the way a slow-moving river meanders and changes.
With global warming, overall air temperature has gone up 1.8 degrees Fahrenheit, but polar air temperature has increased more than twice that. (Melting polar ice, exposure of more bedrock to warming sunlight creates more dark surfaces to absorb even more sunlight heat.) This reduces air temperature differences between polar and temperate zone air even more, which then causes a slower and more meandering jet stream flow.
This year, the jet stream wandered so much that it affected the polar vortex, causing it to break into two separate polar vortexes. On Jan. 28, one “daughter” polar vortex air mass was identified over Norway, Finland, Siberia and the north pole, while the other had wandered down over the Upper Midwest and drifted east toward New England. At the same time, Alaska and northern Greenland were quite warm (above freezing) because frigid polar air was elsewhere. When the polar vortex affecting us in the Midwest moved east, it was followed by unseasonably warm air flowing up from the south, creating the rapid thaw we now have.
As polar temperatures continue to warm (although still bitterly cold by our experience), we can expect more unpredictable and unusual winter weather extremes like this in future years. Thus, our recent severe cold spell was not proof that global warming is fiction, but actually is explained by known meteorology basics, and is a taste of even more similar polar events during otherwise warm winters.
I have to ask why this information has not been a key part of mainstream news media covering this massively disruptive national weather event.