View of the current Polar Vortex on a temperature anomaly map
This view is looking directly down at the N. Pole which has temps way above normal and huge pockets of extreme cold pushed down around the N. Hemisphere.
Snip>The general assumption is that reduced snow cover and sea ice reflect less sunlight and therefore evaporation and transpiration increases, which in turn alters the pressure and temperature gradient of the polar vortex, causing it to weaken or collapse. This becomes apparent when the jet stream amplitude increases (meanders) over the northern hemisphere, causing Rossby waves to propagate farther to the south or north, which in turn transports warmer air to the north pole and polar air into lower latitudes. The jet stream amplitude increases with a weaker polar vortex, hence increases the chance for weather systems to become blocked. A recent blocking event emerged when a high-pressure over Greenland steered Hurricane Sandy into the New Jersey coast.[16]
http://en.wikipedia.org/wiki/Polar_vortex
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