While snow fell in the American Deep South, severe storms battered the East Coast, and International Falls, MN, set a new temperature record of -46º F (-43º C) on January 21, the northern regions of the United States and southern Canada experienced above-normal temperatures. In fact, the unusual warmth forced residents of Iqaluit, capital of the Canadian territory of Nunavut, to cancel their New Year’s snowmobile parade.
Is there a connection between our colder, snowier winters in the North Atlantic and the warmer temperatures across the Arctic? According to the Earth Observatory findings, the overall configuration of warmer-than-normal temperatures in the north and cooler-than-normal temperatures in the south probably results from a climate pattern known as the Arctic Oscillation (AO).
The AO is an index that refers to variations of the opposing atmospheric pressure patterns between the Polar regions and the northern/middle latitude regions, which include the North Atlantic states and Europe. The AO fluctuates between “positive” and “negative” phases. The positive phase causes the more familiar weather patterns, with lower temperatures in the Arctic regions and higher temperatures in North Atlantic. The opposite is true of during a negative phase, which brings higher temperatures to the Polar regions and drives colder air south.
According to researchers at the National Snow Data Center, the Arctic Oscillation alternated between its positive and negative phases during most of the past century. Since in the 1970s, however, the oscillation has tended to stay in the positive phase, causing lower than normal Arctic air pressure and higher than normal temperatures in much of the United States and northern Eurasia.”
The Earth Observatory data presented here show that the AO went into negative phase in the Northern Hemisphere during the winter of 2009–2010. It was in negative mode again in the winter of 2010–2011, affecting temperatures across the Northern Hemisphere. If the AO continues in its negative phase, we will be seeing more of the record-breaking temperatures and snowfalls that have blanketed much of the US northeastern and Midwestern US.
Read the full press release: This Image of the Day, posted by The Earth Observatory on January 26, 2012