北极海冰的变化特征

THE VARIATION FEATURES OF THE ARCTIC SEA ICE

本文使用了北极海冰1972～1989年的资料，分析了北极海冰的区域特征、季节变化和长期变化的特征。发现由于北极海冰南侧被殴亚和北美大陆所包围，处于基本封闭状态，只有通过白令海峡与太平洋相连和格陵兰海和挪威海与大西洋相连的两个通道，其环境条件与南极海冰绝然不同，因此其特征也明显不同。1．季节变化小。净冰面积冬季是夏季的2倍左右，而南极海有6倍之差。2．海冰寿命较长。以多年冰为主，平均寿命为13年。而南极冰多为当年冰。3．4北冰洋海冰区域性差异较大。Ⅰ区冰（90°E～180°～90°W）南面通过白令海峡与太平洋相连，其变化主周期为4年，并有2年、1年和半年等多种振荡周期，这些周期与太平洋海温场的周期大致相同。Ⅱ区冰（90°Ⅳ～0°～90°E）南面与大西洋相连，其主周期为5年，几乎可认为是单周期的变化。另有两个极不显著的弱周期2年和4个月。4．全北极海冰的长期变动趋势从80年代中后期明显减少，Ⅰ区比Ⅱ区更明显。因此认为此原因可能与80年代几次强的E1Nino事件有关，是否与全球气温暖化有关是一个有待今后进一步研究的问题。

In this paper, the regional features, the seasonal variation as well as the secular change of the Arctic sea ice have been analyzed with the Arctic sea ice data from 1972-1989. Enclosed by the European and Asian continents, the Arctic sea ice connects with the Pacific Ocean and the Atlantic Ocean only through the Bering Sea and the Greenland Sea. The geographic condition of the Arctic is therefore very different from that of the Antarctic. Compared with the Antarctic sea ice, the Arctic sea ice has the following features:1. The seasonal variation is less than that of the Antarctic sea ice. In wint er, the net ice area is twice as mucli as that in summer (in the Antarctic, however, the difference between winter and summer is upto 6 times).2. Sea ice life in the Arctic is longer than that in the Antarctic. The average period is 1 .3 years. (In the Antarctic, there is only first-year ice).3. In the Arctic, there are differences among the different parts of sea ice in different regions. In region Ⅰ (90°E-180°-90°W) (to the south of this region is the Bering Sea and the Pacific Ocean), the main period of variation of the sea ice is 4 years.There are also 2-year, 1-year and half-year periods. These periods are related to the sea temperature field of the Pacific Ocean. In region Ⅱ (90°W-0°-90°E), the change of sea ice is almost of single-period (5 years) in addition to which there are two periods (2-years and 4-months) that are not obvious.4. There has been less secular variation of the Arctic sea ice since the middle of the 1980's. This is more obvious in region Ⅰ than in region Ⅱ. The possible reason is that there were several EL Nino events in the 1980's. Whether it is related to the global warming needs further study.