Sea Ice Concentration

Sea-ice concentration is the fraction of a given ocean area covered by sea ice, reported as a percentage or a fraction from 0 to 1. It is the primary variable mapped from satellite passive microwave radiometers (SMMR, SSM/I, AMSR), which exploit the contrast in microwave emissivity between open water and ice, available daily since 1978. Concentration defines the ice edge (commonly the 15 percent contour) and, integrated over area, gives sea-ice extent. It controls the surface albedo, insulates the ocean from the atmosphere, and modulates air-sea heat and gas exchange. Both Arctic and Antarctic concentration fields are core climate indicators.