Arctic Amplification

Arctic amplification is the observed warming of the Arctic at roughly two to four times the global-mean rate over recent decades. The main driver is the sea-ice albedo feedback: as bright, reflective sea ice retreats, open ocean absorbs more shortwave radiation, warms, and delays autumn freeze-up, releasing heat to the atmosphere. Lapse-rate and water-vapor feedbacks, plus poleward heat transport, add to it. The effect is strongest in autumn and winter near the surface. Consequences for navigation include a longer open-water season on the Northern Sea Route and the Northwest Passage, alongside a more variable ice edge that complicates passage planning under the Polar Code.