As we enter a stretch of warmer temperatures, it’s worth noting other places that are getting warm. Chiefly, the arctic, where above-average temperatures caused sea ice to melt to a new low record for January.
You can see where the ice has receded in 2011 from its historical January average between 1979 to 2000, shown as a yellow line on the satellite map above from the U.S. National Snow and Ice Data Center. Several large masses of water that usually freeze over by late November, like the Hudson Bay and the Davis Strait, remained liquid at the surface until the middle of last month.
Temperatures in some cases were as high as 14 degrees above average. Here’s a map showing temperature abnormalities from November until the beginning of February, from the National Centers for Environmental Prediction (note the scale is in Celsius):
So if it’s so mild up there, why has our winter been so uncharacteristically cold and snowy?
Government scientists have put forward a couple explanations. The first is that the Arctic Oscillation was locked into a particularly long negative phase this year. The oscillation is basically a pattern of pressure differences over the high northern latitudes. When it’s positive, a band of high pressure over the middle latitudes keeps cold, low-pressure air locked into the Arctic region. During negative phases that high-pressure band weakens, allowing cold polar air to scoop downward into the middle latitudes.
The oscillation typically phases back and forth over the course of weeks, but this year for some reason it stayed negative for all of December and January. And as the frigid air seeped out from the Arctic and unleashed heavy snows in Europe and North America, warm air rushed up to the pole to replace it. Thus the mass melting of ice.
Another theory that the government is considering is that already low levels of sea ice could be contributing to the Arctic warming. Sheets of shiny ice act as a mirror for solar heat radiation and reflect it back into space. But vast expanses of dark ocean water help absorb the sun’s energy, warming up and melting more ice.
And of course there are many other theories relating to north Atlantic ocean cycles, snow pack in Siberia, etc. Nobody really knows what’s behind these massive shifts in polar weather patterns; that’s why it’s so important to keep the research going.
One thing for sure? It probably doesn't have anything to do with Godzilla.