Most of us know that the Arctic summer sea ice is melting at a record pace.  A group of international climate change scientists has written a paper for Geophysical Research Letters that may explain the change in speed - a significant change in the atmospheric circulation pattern in the Arctic that has occurred since 2001.  Here's what the German newspaper, Der Spiegel, says about it:

"Winter in the Arctic has long been determined by what researchers refer to as a "tri-polar" pattern. The interaction among the Icelandic Low, the Azores High and the subtropical high in the Pacific led to primarily east-west winds, a pattern which effectively blocked warmer air from moving northward into the Arctic region.

"But since the beginning of the decade, the patterns have changed. Now, a "dipolar" (bipolar) pattern has developed in which a high pressure system over Canada and a low pressure system over Siberia have the say. The result has been that Arctic winds now blow north-south, meaning that warmer air from the south has no problem making its way into the Arctic region.  "It's like a short-circuit," says Rüdiger Gerdes, a scientist at the Alfred Webener Institute for Polar and Marine Research and one of the five authors of the study."

Der Spiegel also has maps of the two circulation patterns.

James Overland from the Pacific Marine Environmental Laboratory in Seattle told Der Spiegel, "If the current flows stay the way they are, then we will see the disappearance of Arctic sea ice 40 years earlier than we would as a result of greenhouse-gas emissions alone.  If the Arctic circulation were to return to normal and would switch to the "dipolar" pattern just once in a decade, the situation would look grim, he said. "Each time we would see a loss of so much ice that it would be impossible to return to the initial state."

Hat tip to JohnnyRook at DailyKos