北极楚科奇海海冰面积多年变化的研究

Study on the multi-year variations of sea ice cover of Chukchi Sea in Arctic Ocean

北极气候系统正在发生显著变化，其中，海冰面积和厚度的减小是其最主要的特征．楚科奇海是海冰面积变化最有代表性的区域．文章利用积累了9a的高分辨率海冰分布数据研究海冰面积的多年变化特征．结果表明，各年的冰情有显著的季节内变化，海冰面积距平曲线体现了不同时期海冰面积变化的动态过程．在1997～2005年间，楚科奇海海冰面积经历了轻（1997年）—重（2000-2001年）—轻（2002-2005年）的变化过程．9a的数据总体上体现了海冰面积减小的趋势，2005年的冰情呈现了历史新低．每年融冰期的长短与冰情轻重有密切的关系，冰轻年份融冰开始时间早，冻结结束时间晚．各年海冰面积最小值发生在9月下旬至10月初，各个年份海冰最小面积差别很大．有的年份只有4％，而重冰年可以大于50％．文章采用4个重要参数表达海冰多年变化．其中海冰面积指数反映了当年总体平均的海冰面积距平；海冰最小面积反映了融冰期海冰的极限情况；上一个冬季的气温积温也与翌年海冰面积有良好的关联；分析了风场对海冰的影响，表明风场在融冰期能够在短时间内改变海冰的覆盖面积．

The Arctic climate is experiencing obvious change, and the variations in the area and thickness of sea ice are the uppermost characteristics. The ice cover in the Chukchi Sea represents mostly the variation of Arcitc sea ice cover. In this paper, the variations of ice area within nine years in the Chukchi Sea are studied by using the remote sensing sea ice data. The results show that the annual difference of sea ice area is notable in different year. During the years of 1997-2005, the ice area underwent a course from light ice year（1997） to heavy ice year（2000-2001） and then regressed light ice years（2002-2005）. As a whole, the ice area presents a decreasing trend, and the ice condition was the lightest in the year 2005. The duration of ice melting correlated well with the ice condition. In the light ice year, the melting begins earlier and freezes-up later. The minimum sea ice cover appear in the late September to early October each year, whose areas are quite different, 4% in the light ice years and more than 50% in the heavy ice years. Some major indices, Sea Ice Area Index, Minimum Sea Ice Area, Accumulated Temperature Anomaly and two Wind Driven Indices are chosen to express the multi-year variations of the sea ice cover and the impact from local climate. The Accumulated Temperature during winter has obvious impact on the ice condition of the coming year. Local wind field is a key fact to change the ice cover in short time by causing the compression or extension of low concentration ice in summertime.