Wednesday, 29 January 2014

Life in the Freezer: What’s the Deal with the Polar Vortex?

Special thanks to Emma in Kitchener, Ontario, Canada for suggesting this week's bone-chilling topic.

If you’ve spent much time east of the North American Rocky Mountains this winter you may have born witness to some freakishly cold weather. Cold snaps happen every now and then but what has been going on from the Canadian prairies all the way down to central Florida beginning in late December and peaking during the first few weeks of January has been pretty unprecedented. News outlets have taken to calling it “The Polar Vortex” because, quite frankly, that sounds awesome. But what has really been going on this winter?

Believe it or not (and I was incredulous to start) the Polar Vortex is not just a great buzz-term invented to sell newspapers. It is a real thing and most of the time it is a very good thing. Basically, as the Earth spins it causes wind to bend, blowing in a curve rather than a straight line. Meteorologists and fans of The Simpsons know this bending at the Coriolis Effect and it is at its most extreme at the North and South Poles. The bending is so extreme over the poles that the wind blows in a complete circle and creates what amounts to a massive hurricane. If you’ve ever seen footage of an arctic blizzard, you’ve seen the Vortex on home soil. The good news for people who live at more reasonable latitudes is that the  vortex traps freezing cold air at the top and bottom of the world

The problems that have arisen this winter have been the result of rapid warming over the Arctic Ocean. The phenomenon is called Sudden Stratospheric Warming (SSW) and we have known about it since the mid 1900’s. Essentially, when the polar stratospheric air rises in temperature by a few dozen degrees (K) over a period of about a week the usually stable Polar Vortex gets disrupted. It can no longer hold the coldest air on the planet in place and that air rushes south to the dismay of those guys who try to wear shorts all winter. The bone-chilling temperatures experienced across the continent haven’t just felt like arctic winds, they literally are arctic winds. The effect has been worsened by a slow jet stream failing to bring warm air from the south to combat the frigidity. To mix my movie references, it is a Perfect Storm straight out of The Day After Tomorrow.

So how bad has it been, really? Is this cold snap anything to write home about or are North Americans just getting a little wimpy? Well, if you were in Toronto or Chicago on January 7th (both hovering around -27 degrees C (-16 F)) you would have been better off at the South Pole (-21 C/-6 F). Interestingly, if you heard that Winnipeg, Manitoba was colder during the icy blast than the surface of Mars, you were both well-informed and grossly misled. It turns out equatorial Mars can reach temperatures of 27 C (81 F). Who knew?

Regardless of Martian weather, it has been impressively cold. New Year’s Eve in Winnipeg dipped down to -37.9 C (-36.2 F). Green Bay, Wisconsin set a record low on January 5th when it hit -28 C (-18 F).  And even the city of Saltillo in Mexico went subzero, recording a temperature of -6 C (21 F) on January 14.

Whenever something like this happens climate change skeptics are chomping at the bit to say something annoying like “So much for global warming!” When that happens to you, informed reader, feel free to share the fact that some researchers have suggested (even before the events of Dec-Jan 2013/14) that rising temperatures at the poles could disrupt the Polar Vortex and lead to extreme weather events (Weng, 2012). As anyone who has seen An Inconvenient Truth can tell you, temperature fluctuations are expected to be most severe around the Arctic and Antarctic.

So is this the new normal? Can people living on the leeward side of the Rockies start investing in dogsleds and parkas? It’s way too early to say, but probably not. Freaky weather happens from time to time, especially in the winter. The most we can do is keep an eye on things and adapt. If it turns out that we humans have accidentally flipped the freezer switch to high, we’re going to have to learn to live with it. At least we have Dennis Quaid to help with survival advice.

Full Journal Reference:

Weng, H. (2012). "Impacts of multi-scale solar activity on climate. Part I: Atmospheric circulation patterns and climate extremes". Advances in Atmospheric Sciences, 29 (4): 867–886. doi:10.1007/s00376-012-1238-1