A historic polar low

A tiny, but historic polar low

This satellite image was taken on 8 January 2010, and as far as I’m aware, it’s the first polar low to have been spotted north of Spitsbergen (the biggest island in the Svalbard archipelago). It is also the first one I’ve seen to form north of 80N (the curve just below the PL). It’s not big, but it’s pretty.

Polar lows usually form much further south. The traditional hot spot is near the entrance to the Barents Sea, just north or north-west of the Norwegian mainland. But in recent years it has become clear that PLs occur quite often in other regions as well, such as in the Labrador Sea. Japan has its fair share of PLs each winter, too.

The PL north of Svalbard is interesting because I think PLs will become much more common in the high Arctic as the sea ice retreats. Polar lows can only form over open ocean, so there haven’t been any in the large parts of the Arctic that are covered with sea ice throughout the winter. Now that the Arctic sea ice is shrinking, there is suddenly a potential for PLs to form, and I think they will. All they need is some (in relative terms) warm water and freezing air. They have that in the Arctic.

In a paper that Tom and I wrote in 2007, we tried to find out how the potential for PLs was going to change in this century according to climate models. Here is the map that we compiled, using simulations from 13 models:

Projected changes to our marine cold air outbreak index during the 21 century

The details about what is shown in the figure can be found in the paper, but the red colours indicate large positive changes to the probability of PLs to form. (The negative, bluish colours indicate a declining likelihood, see also Zahn and von Storch, Nature, 2010)

What the red colours mean is that where the sea ice is retreating, there’s going to be a lot more polar low-like weather in the future. But there is a caveat. The climate models that we looked at had to much sea ice to begin with, so the projected changes along the southern rim of the Arctic Ocean are unrealistically large. However, I believe that in regions such as the north-eastern Barents Sea, the Beaufort Sea and the Chukchi Sea, where there is sea ice today, polar lows and similar weather phenomena are going to become more and more common in the future. This is probably bad news for the companies that plan to start using these regions for oil and gas exploration and transport.

To come back to the PL in the first picture now, it’s a small one, but it could be a taste of the future in the high Arctic. I plan to try to model it using a weather forecasting model to see what actually happened. More on that later.

Cheers, Erik

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