Unraveling the Polar Vortex

(Image source: winnipegfreepress.com)

We’ve been hearing a lot lately about the Midwest’s recent foray into subzero temperatures and how it’s connected to the so-called “polar vortex,” which sounds terrifying and dramatic but in truth is neither. Its sudden appearance resulted in shockingly low temperatures across the country, with wind chills reaching well below zero into those depths of temperature that give you frostbite just thinking about them.

The vortex that has managed to sweep down across the US is nothing new though. As Rob Oravec, of the National Weather Service, told National Geographic, “The atypical part of this weather pattern is some of these really cold temperatures are going to be pressing into parts of the country that don’t typically see that magnitude of cold in early winter.” The polar vortex is a fairly constant phenomenon where frigid pockets of air circulate near both the North and South poles. In the North, there are usually two centers around which the vortex revolves, one over Baffin Island in Canada and one in northeast Siberia. In the Southern hemisphere, it usually rotates around the Ross Ice Shelf.

What happened over the past few days was fairly simple. The faster the vortex moves the tighter its circulation is, so as it slows, it will dip further down into the Northern US, which it began to do at the beginning of January. Normally the jet stream that runs between the cold air up north and the warmer air down south keeps the polar vortex’s icy breath contained.

But this time we saw some low level disturbances to the jet stream that led to a “kink” forming in the normally west-east line of quickly moving air. As a result of that kink, we ended up getting hit with those record breaking lows we’ve all been lamenting every time we have to get the mail or go to the store.

As temperatures rise in the Arctic, the jet stream that runs East to West across the United States will continue to weaken, leading to more erratic and extreme weather patterns (Image source: http://www.washingtonpost.com)

So why did the polar vortex slow down? Why did the jet stream get a kink in its normally oh-so-reliable pattern? Well as you can expect the issue of global warming falls front and center with this. Many doubters pointed to these record lows as evidence of global warming being a hoax, although to be honest they probably would have been saying regardless of the weather (oh and this too, I guess). But in truth, climate change is most likely the cause of this recent American arctic adventure.

As ice and snow continue to disappear in the Arctic, less light is reflected. Thus temperatures will increase in those northernmost regions. The jet stream that helps to contain the polar vortex moves faster when the difference between northern temperatures and southern temperatures is higher. As Arctic temperatures rise, that difference shrinks, and so the jet stream weakens, thus making it much more likely that we end up with those biting polar vortex winds chilling us to the bone. To learn more about the jet stream or most anything with climate science, check out the National Weather Service’s website. It’s fairly in-depth if you’re into that.



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