Over the last month, the high Arctic in Canada has been experiencing record warmth -- with the average temperatures over a 29-day period more than 21 degrees above normal.
A year ago, during the winter of 2009/10, Canada experienced its warmest and driest winter since records began. The anomaly was blamed on medium-strength El Niño, which tends to send warmer-than-average air over Canada. News organizations covered the break-up of ice in Iqaluit -- the capital of normally icy Nunavut -- which endangered the snowmobile race that the local people run on Frobisher Bay.
This year, the snowmobile race couldn't run at all. There was no ice to break up, despite a very strong La Niña -- the reverse of El Niño conditions -- taking place in the Pacific, which should have sent cold air pouring across the top of North America.
Instead, it appears that the North Atlantic Oscillation (NAO) has had a strong influence on the region's climate, with a strongly negative NAO blocking the jet stream that normally keeps cold air up in the far Arctic north, and the open water that remains has got the region caught in a positive feedback loop. Instead, that cold air has poured down over Europe and the United States, creating bitterly cold, snowy conditions that have dominated most media coverage of the weather this winter.
The temperatures in Canada have been far more extreme, though. In one location -- Coral Harbour in Nunavut -- a typical mid-January day's temperature will peak at -26C, and sink to -34C at night. On cold years, it'll sink lower than that. After New Year's Day 2011, lowest daily temperatures in Coral Harbour stayed above the average high mercury mark for 11 days straight. On 5 and 6 January, temperatures rose above 0C -- something that's never been recorded during January, February or March. On 6 January, the lowest temperature recorded was just above -4C -- 30 degrees above the average low temperature for that time of year.
The effects are being felt on the population. David Phillips, a senior climatologist with Environment Canada, told UCAR: "It's impossible for many people in parts of the eastern Arctic to safely get on the ice to hunt much-needed food for their families -- for the second winter in a row. Never before have we seen weather impact a way of life in so many small and big ways."
Behind the scenes lurks the spectre of climate change. While it's impossible to make a definitive link between the conditions of an outlier year and a slow but steady increase over decades, the feedback effects seen this year will magnify growing future impacts into a considerably greater threat than they might otherwise be. Whatever happens, keeping an eye on how the NAO will affect a warming atmosphere will likely remain a priority for climatologists.
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