An oscillation, approximately decadal in length, in the atmospheric parameters over the Arctic and those in a zone centred at approximately 40° N. When the polar vortex is strong and extends down to the surface, the Arctic surface air pressure decreases, the westerly zonal flow increases in strength, moves northwards, and transports more heat to northern Europe and the polar region causing a decrease in Arctic ice cover. In the opposite phase, there is a sudden warming, the strength of the vortex declines, and the westerlies track farther south. It is essentially the same phenomenon as the North Atlantic Oscillation. A similar feature, the Antarctic Oscillation, occurs in the southern hemisphere.
Subjects: Meteorology and Climatology.