A polar vortex, also called polar cyclone, is a persistent large-scale cyclone occurring seasonally near either of a planet’s geographical poles. The phenomenon first appeared in winter in the Northern Hemisphere and was discovered in 1952 with radiosonde observations. In the Northern Hemisphere, the Arctic vortex has two centres: one near Baffin Island and one over northeast Siberia. In the Southern Hemisphere, it is usually located near the Ross Ice Shelf. Polar vortices tend to be weaker in summer.

How does it form?

Their formation is quite similar to the formation of hurricanes in tropical regions and is also caused by the Coriolis effect: fast moving winds build up around a calm centre. However, unlike hurricanes, they are frigid polar winds, circling the Arctic at more than 100mph. The spinning winds trap the cold air in the Arctic. They can form any time of the year.

Why can it be destructive?

Polar circles are rarely destructive since they appear in areas with little or no population. The problem is that they sometimes weaken or split apart, propelling the cold wind patterns out of the Arctic into our sky. In fact, when they weaken, they are more likely to break and become a factor in our winter weather. Scientists have said that global warming in the Arctic could be responsible for the weakening of the polar vortex.

 National Science Foundation via Wikimedia

Photo source : Ian Mackenzie, http://flic.kr/p/4F3QGZ, (CC BY 2.0)