Polar lows in the future

In September 2010, Nature published an interesting article on the future of polar lows. [Read and download it here]

A good friend of ours, Matthias Zahn, who like us did his Ph.D. on polar lows, performed an interesting experiment with Hans von Storch. Recognizing that climate models are unable to simulate actual polar lows (because their resolution is too low), they had to find another way to tell if the frequency and severity of polar lows will change in the future. They therefore took the results from one of the models and fed them into a high-resolution regional climate model (pretty much the same as a weather forecasting model), to “translate” the climate model output to more realistic weather.

In Zahn and von Storch’s simulations, the number of polar lows decreased quite a lot for the future scenarios that they used. The reason for this was that in a warmer future, the air heats up faster than the ocean. This makes cold air outbreaks occur less often (because the air isn’t so cold anymore), and as a consequence, you get fewer polar lows. Tom and I did a similar analysis using the same climate models a few years ago [download paper here], and came to the same conclusion: in the typical polar low regions the frequency of polar lows is going to decline in the future. But the other half of our conclusion was:

In the regions that are covered by sea ice in today’s climate, the number of polar lows will increase dramatically if the sea ice retreats.

I expect this to be true for many regions near today’s sea ice edge, such as the north-eastern Barents Sea, north of Russia (the Kara and Laptev and East Siberian Seas), north of the Bering Strait (the Chukchi Sea) and north of Alaska (the Beaufort Sea). The reason is that polar lows need open ocean and cold air, and when the sea ice disappears, they get just that.

This story was picked up by Reuters in 2009 [read the article here], and was published on many web sites (Scientific American, USA Today etc.). Zahn and von Storch’s paper got a lot of attention; see for instance this article in the Guardian.


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