Europe's deadly cold snap may have a lot to do with shrinking amounts of ice in the Arctic, a recent study suggests.
Nearly 300 deaths have been reported across the continent, with snow accumulations not seen in five decades reported in some places. Warsaw, Poland, has seen 11 days of temperatures well below average, with a coldest reading of 35 below zero Fahrenheit.
Scientists at the Alfred Wegener Institute for Polar and Marine Research in Potsdam, Germany, say the frigid, snowy European winter has its origins in a warm Arctic summer.
The U.S. National Oceanic and Atmospheric Administration reported that July 2011 was the fourth-warmest July on record. A warm summer in the Arctic cuts the amount of sea ice. NOAA reports that sea-ice levels last July were the lowest in three decades.
The effect is twofold, the Wegener scientists report.
First, less ice means less solar heat is reflected back into the atmosphere. Rather, it is absorbed into the darker ocean waters. Second, once that heat is in the ocean, the reduced ice cap allows the heat to more easily escape into the air just above the ocean's surface.
Because warmer air tends to rise, the moisture-laden air near the ocean's surface rises, creating instability in the atmosphere and changing air-pressure patterns, the scientists say.
One pattern, called the Arctic Oscillation, normally pushes warm Atlantic air over Europe and keeps Arctic air over the poles.
But in mid-January this year, the Arctic Oscillation abruptly changed, allowing the jet stream to plunge into Siberia and push cold and snowy weather over much of Europe.
Similar situations have emerged the past two years.
Check out some more reports on what this winter's been like, both in the U.S. and around the world: