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Erik W. Kolstad
Bergen, Norway
PhD, meteorology
Interests: Arctic storms, polar lows, seasonal forecasting, wind energy, climatology, numerical modelling
Recent Activity
Hi guys, great to see so much interest in this storm. I did my PhD in meteorology on extreme weather in the Arctic, mainly focusing on polar lows (or Arctic hurricanes, as they were once called by Kerry Emanuel and others). I just wanted to briefly comment on the probability for Arctic storms when the sea ice retreats. First of all, polar lows are small-scale storms that feed on the energy being released by the (relatively) warm ocean when very cold air masses emigrate south from the Arctic sea ice cap. In this sense they're similar to tropical cyclones. The storm that we're seeing now is not a polar low. They only occur from autumn to spring (in the polar night), because that's the only part of the year that the air gets cold enough for the enormous heat fluxes from the ocean to the atmosphere that drive polar lows to occur. Also, they move south, away from the ice, embedded in cold air outbreaks. The current storm moved in from Russia and merged with an existing low over the ice cap. Jeff Masters pointed out that the low is stacked with an upper low, and this "barotropic" structure is usually a sign that the low will weaken quite soon. Generally speaking, it is likely that Arctic storms will become more frequent as the sea ice retreats. This will probably be more noticeable in late autumn and early spring, but maybe also during winter. The reason for this is that the waters in regions that were previously covered by sea ice will become exposed and thereby open up reservoirs of energy to be used as fuel for the storms. I've looked at this effect for polar lows, and in a study that I did with Tom Bracegirdle of the British Antarctic Survey, we concluded that the breeding grounds of polar lows will emigrate further north, following the retreating sea ice. Other kinds of storms will probably also be able to penetrate further north than they currently do, following their energy source, the open water. Although storms are predominantly a winter phenomenon, retreating sea ice may lead to more frequent Arctic storms in the summer as well. This is because most storms (tropical cyclones are one notable exception) feed on horizontal temperature gradients. The temperature difference between the Arctic and the tropics in the dark season is what generates the jet stream and the large, synoptic lows that can grow so powerful from autumn to spring. And as the sea ice retreats, the local temperature gradients will increase and probably raise the risk of summer storms. I hope this makes sense. Cheers, Erik Kolstad Bergen, Norway
Toggle Commented Aug 9, 2012 on Arctic storm part 3: detachment at Arctic Sea Ice
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Aug 9, 2012