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Arctic warms while Europe and L48 freeze Unusual weather pattern sweeps frigid air south while warmer than normal conditions in North Atlantic reduce rate of sea ice formation Alan Bailey Petroleum News
Newsreel shots of blizzards in central Europe, the sight of snow storms in Oklahoma and reports of Arctic-like temperatures in Scotland and Scandinavia may leave people wondering what the weather has been like in the Arctic, where seriously cold conditions normally prevail at this time of year.
But the Arctic and the extreme northwestern part of North America were unusually warm in December, causing the Arctic sea-ice extent to remain below normal, especially in the Arctic regions of the North Atlantic, the National Snow and Ice Data Center reported Jan. 5.
“Average air temperatures over the Arctic Ocean were much higher than normal for the month, reflecting unusual atmospheric conditions,” NSIDC said.
How come? Arctic oscillation December saw an extreme negative phase of a climatic feature called the Arctic oscillation, resulting in a major change in wind patterns and an unusual pattern of temperatures in the Earth’s northern hemisphere, NSIDC said.
It’s all to do with the distribution of air pressures at low altitudes in the atmosphere. Low atmospheric pressure normally characterizes the northern polar region, with a counterbalancing area of relatively high pressure at mid-latitudes. In the North Atlantic, this pressure pattern gives rise to prevailing southwesterly winds that bring warm, moist air into northern Europe, causing, for example, the legendary grey skies, rain and mild temperatures of the British Isles.
The term “Arctic oscillation” refers to variations over time in the pressure levels in the pressure pattern. In a positive phase of the oscillation the atmospheric pressure in the Arctic is especially low, while in a negative phase the pressure is abnormally high. And this winter the negative phase dropped to the lowest negative value observed since 1950, shifting the normal warm southwesterly air flow in the Atlantic and causing temperatures in Europe to plummet to levels not seen in decades.
Warm air At the same time the higher-than-normal pressure in the Arctic lodged warmer-than-normal air in the region.
“The strongest anomalies (more than 7 C/13 F) were over the Atlantic side of the Arctic, including Baffin Bay and Davis Strait, where ice extent was below average,” NSIDC said.
But a negative phase of the Arctic oscillation affects the winds that typically blow sea ice out of the Arctic Ocean and could, as a consequence, end up retaining second- and third-year Arctic sea ice and rebuilding some older multiyear ice, NSIDC said.
Meantime, the average Arctic Sea ice extent in December was 26,000 square miles, the fourth lowest extent since the start of satellite Arctic ice observations in 1979, NSIDC said.
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