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Mapping of Active Frazil in the Southern Ocean, with Improved Estimation of Sea-Ice Production
  • Kazuki Nakata,
  • Kay I. Ohshima,
  • Sohey Nihashi
Kazuki Nakata
Institute of Low Temperature Science, Hokkaido University

Corresponding Author:[email protected]

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Kay I. Ohshima
Institute of Low Temperature Science, Hokkaido University
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Sohey Nihashi
Department of Engineering for Innovation National Institute of Technology Tomakomai College, Tomakomai, Japan
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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.