北极海冰变化的时间和空间型

TEMPORAL AND SPATIAL PATTERNS OF ARCTIC SEA ICE VARIATIONS

利用 4 4a(195 1～ 1994年 )北极海冰密度逐月资料 ,分析提出了一种与北极冰自然季节变化相吻合的分季法 ,并根据这种分季法 ,使用EOF分解 ,揭示了北极各季海冰面积异常的特征空间型及其对应的时间变化尺度。结果表明 :(1)北极冰面积异常变化的关键区 ,冬季 (2～ 4月 )主要位于北大西洋一侧的格陵兰海、巴伦支海和戴维斯海峡以及北太平洋一侧的鄂霍次克海和白令海 ,夏季 (8～ 10月 )则主要限于从喀拉海、东西伯利亚海、楚科奇海到波佛特海的纬向带状区域内 ,格陵兰海和巴伦支海是北极海冰面积异常变化的最重要区域 ;(2 )春 (5～ 7月 )、秋 (11月～次年 1月 )季各主要海区海冰面积异常基本呈同相变化 ,夏季东西伯利亚海、楚科奇海、波佛特海一带海冰面积异常和喀拉海呈反相变化 ,而冬季巴伦支海、格陵兰海海冰面积异常和戴维斯海峡、拉布拉多海、白令海、鄂霍次克海的海冰变化呈反相变化 ;(3)北极冰总面积过去 4 4a来确实经历了一种趋势性的减少 ,并且叠加在这种趋势变化之上的是年代尺度变化 ,其中春季 (5～ 7月 )海冰面积异常变化对年平均北极冰总面积异常变化作出了主要贡献 ;(4)位于北太平洋一侧极冰面积异常型基本具有半年的持续性 。

Temproral and spatial patterns of the Arctic sea ice variations have been documented in this study with 44 year (1951-1994) monthly sea ice concentration dataset. A more objective season is defined for describing natural seasonal variations of the sea ice, with winter in February-April, spring in May-July, summer in August-October and fall in November-January. According to such a definition, dominant patterns of the sea ice anomalies in the extent are examined with EOF decomposition. It was found that key regions with large variability of sea ice are located in the Greenland and Barents Seas, the Davis Strait, the Bering Sea and the Sea of Okhotsk during winter, but confined to a zonal area along the Kara, Laptev, East Siberian and Beaufort Seas during summer. Dominant modes of sea ice variability exhibit in phase fluctuations in most of the key regions during spring and fall, yet out of phase fluctuations between the western North Atlantic (the Greenland and Barents Seas) and the eastern North Atlantic (the Labrador Sea and the Davis Strait) together with the North Pacific (the Bering Sea and the Sea of Okhotsk) during winter, and out of phase fluctuations between the East Siberian and Beaufort Seas and the Kara Sea during summer. The annual mean extent of the Arctic sea ice is characterized by a decadal-scale variation superimposed upon a long term diminishing trend over the 1951-1994 period, which is largely attributed to the dominant mode of spring (May-June-July) sea ice variability. Finally, it was also found that the persistence of sea ice anomalies in North Pacific basically is six months, while that in North Atlantic is up to one year.