Mapping of Active Frazil in the Southern Ocean, with Improved Estimation
of Sea-Ice Production
Abstract
The predominance of active-frazil area and the high sea-ice production
associated with it in Antarctic coastal polynyas have been increasingly
recognized in recent in situ and high-resolution satellite observations.
However, the occurrence and spatial distribution of active-frazil area
are not well understood. We present the first mapping of active-frazil
area in the Southern Ocean, based on the thin ice algorithm of AMSR-E
that discriminates active-frazil area. Active-frazil area is predominant
along East Antarctica, particularly very close to the coast, leading to
very high ice-production rates exceeding 20 m/yr. Appropriate
incorporation of active-frazil area improves estimation of sea-ice
production significantly. For frazil-dominant polynyas, estimated ice
production is ~20%–50% higher compared with previous
studies. Analyses of all the major polynyas suggest that active-frazil
extent exponentially depends on offshore wind and air temperature, while
ice production is determined by offshore wind only.