Arctic Oscillation

The Arctic Oscillation is the leading mode of atmospheric pressure variability over the Northern Hemisphere extratropics, defined as a seesaw in sea-level pressure between the Arctic and the mid-latitudes. Its positive phase has lower polar pressure, a stronger circumpolar vortex, and storm tracks shifted poleward, which tends to lock cold air over the pole. The negative phase has higher polar pressure, a weaker vortex, and cold-air outbreaks pushing south. The AO is closely tied to the North Atlantic Oscillation and modulates Arctic sea-ice motion, the Beaufort Gyre, and the transpolar drift, so it shapes the seasonal distribution and export of sea ice through Fram Strait.