The cold facts about the polar vortex

The North East will have a ‘polar vortex’ to contend with in the next few weeks. Cold temperatures are on the way and could bring snow, ice and travel chaos. But what has caused it and why do some experts believe the freezing cold blast it brings is a result of global warming? Here’s everything you need to know.

What is a ‘polar vortex’?

It is the result of a sudden stratospheric warming (SSW) which will bring cold winds from Eastern Europe to the UK. It is a seasonal atmospheric phenomenon, a system of strong, high-level winds – called the jet stream – surrounding an extremely cold pocket of Arctic air.

If it’s a seasonal thing why do we hear of it so rarely?

The polar vortex for the most part is a pretty good thing, because its winds usually form a boundary that keeps the cold air contained and protects us from freezing temperatures.

However it occasionally breaks down a little. The result is a big, powerful blast of Arctic air that can travel far south, causing the temperature to plunge in places accustomed to having mild winters

What causes the polar vortex to break down?

Scientists say it’s usually a bit irregular around the edges, with areas known as troughs where the cold air extends away from the pole, and other areas called ridges, where the warm air pokes toward it.

So why do some believe climate change – or global warming – could be the cause?

Scientists have observed that more and more Arctic sea ice is melting during the summer months. As the ice melts, the Arctic Ocean warms, and radiates that excess heat back to the atmosphere in winter.

Because that heat somewhat reduces the contrast between the Arctic air and the atmosphere in regions farther south, it reduces the intensity of the winds that form the barrier between the two areas.

That, in turn, weakens and disrupts the polar vortex.