北极海冰快速减少期间加拿大海盆上层海洋夏季淡水含量变化

SUMMER FRESHWATER CONTENT VARIABILITY OF THE UPPER OCEAN IN CANADA BASIN DURING RECENT SEA ICE RAPID DECLINE

北极海冰近年来快速减少,北冰洋淡水含量也出现了急剧变化。加拿大海盆作为北冰洋淡水的主要存储区域,研究其淡水含量变化对于认识北冰洋淡水收支有重要意义。本文根据2003年、2008年中国北极考察以及2004年至2007年的加拿大考察数据进行计算,发现除2006年以外,夏季加拿大海盆淡水含量在此期间每年增加1 m以上厚度。增加主要发生在冬季白令海水以上的上层海水中,而在此之下,淡水含量维持在3 m左右,没有显著年际差异。在2006年,加拿大海盆西部上层淡水含量略微减少,但东部和北部海域淡水含量仍略有增加。与2003年相比,2008年加拿大海盆中心海区淡水含量增加量最高可达7 m。分析表明,近年来的海冰减退对加拿大海盆上层淡水含量的增加起着重要作用,北极涛动(AO)正负相位变化也是控制其淡水含量变化的一个重要因素,而降水、径流以及白令海峡入流水的变化对加拿大海盆淡水含量变化影响较小。

Freshwater content（FWC） in the Arctic Ocean has changed rapidly in recent years,in response to the significant decrease in the extent of the sea ice.Research on freshwater content variability in the Canada Basin,the main storage area of fresh water,is important for understanding the input-output of freshwater in the Arctic Ocean.The FWC in the Canada Basin was calculated using data from the Chinese National Arctic Research Expeditions of 2003 and 2008,and from expeditions of the Canadian icebreaker Louis S.St-Laurent from 2004—2007.Results show that the upper ocean in the Canada Basin became continuously fresher from 2003 to 2008,excepting 2006.The FWC increased at a rate of more than 1 m·a-1,and the maximum increase between 2003 and 2008 of 7 m was in the central basin.Variability of the FWC was almost entirely limited to the layer above the winter Bering Sea Water,below which the FWC remained around 3 m during the study period.Contributors to the FWC increase are generally considered to be net precipitation,runoff changes,Pacific water inflow through the Bering Strait,sea ice extent,and the Arctic Oscillation（AO）.However,we determined that the first three contributors did not have any apparent impact on the FWC changes.Therefore,this paper focuses on the analysis of the latter two factors and the results indicate that they were the major contributors to FWC variability in the basin.