Relation of ice conditions to climate change in the Bohai Sea of China

The ice conditions in the Bohai Sea and the northern Huanghai Sea greatly change from year to year with winter climate.Ice only covers below 15% of the the waters during the warmest win ter,while it covers more than 80% during the coldest winter.Ice observation and data acquisition are outlined in the paper.The ice-covered area,the position of ice edge and the ice grades give indication of the ice conditions.The local climate of the waters can be expressed by using the air temperature of the stations of Dalian and Yingkou.The variation of the ice condition indexes with the monthly mean air temperature at Dalian from 1952 to 2000 is shown,as well.The local climate and ice conditions in the waters are affected by many factors,such as,evolution of the general atmospheric circulation and the solar activity.The delayed correlation between the ice conditions and lots of the affecting factors is analysed in the paper.The ice conditions are continuously mild since the 1990s,that is relative to the tendency of the global warming.The ice condition variation of the Bohai Sea is related to the El Niño event and the sunspot period.The seasonal evolution of the ice conditions is also described in the paper.