According to one researcher, "The Arctic Dipole pattern occurred in all summer months of 2007 and helped support the record 2007 summer reduction in sea ice extent (Overland et al., 2008). Fall 2008 through spring 2009 featured the old AO pattern. The new Arctic Dipole pattern re-appeared in June - July 2009, but the old AO pattern dominated in August - September, resulting in greater sea ice extent than in 2007 and 2008. The Arctic Dipole pattern was active again in October, inactive in November, and is reasserting itself this December."
Regardless of your viewpoint on climate change, the Arctic Dipole represents a fundamental new change in atmospheric circulation in the Northern Hemisphere, one that has not been seen before, and is appearing with increasing regularity. It's likely to help speed the loss of ice from the arctic region in coming years.
Friday, December 11, 2009
The Arctic Dipole
A little background. In the latter part of the 20th century, a new and never-before seen weather pattern emerged in the arctic region called the Arctic Dipole anomaly. Typically in the winter months, the Arctic Oscillation results in winds circulating around the pole in a circular fashion, keeping sea ice restricted to the Arctic Basin. Higher air temperatures in the lower arctic atmosphere have resulted in changes in atmospheric circulation in which the classic arctic high is shunted off to the side while south to north winds bring warmer air into the polar region and also push sea ice out into the general region of the North Atlantic. The mechanism is observed to be heating of the ocean in areas of extreme summer sea ice loss, directly impacting surface air temperatures over the Arctic Ocean. As a result, the Arctic Dipole has been increasingly evident in the arctic in recent years and months.