Analysis on long term variations of seasonal sea ice extent and its climatological interpretation

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Sea ice fluctuations in the sea of Okhotsk was investigated by using the daily sea ice map. A new ice map was made to indicate thin/thick sea ice coverage. The algorithm for thin ice observations was developed by the University, of Washington, NASA and also by ourselves. Sea ice extent seems to be affected by the early winter conditions. Seasonal trends was observed in the extreme year ; cold/warm, then sea ice extent showed faster/later trend in the corresponding winter.Daily polynya fluctuations were investigated. The accumulated advances of polynya area in winter reflect the variation of maximum sea ice area of the corresponding winter.An isolated sea ice area was observed in the warmer winter, 1995196 and 1996/97. Its distribution and stability are similar to the Odden ice pattern in the Greenland Sea. This phenomena was observed only in the two years in the recent 10-years data.