Summer freshwater content variability of the upper ocean in the Canada Basin during recent sea ice rapid retreat

摘要

Freshwater content (F W C) in the Arctic Ocean has changed rapidly in recent years, in response to significant decreases in sea ice extent. Research on freshwater content variability in the Canada Basin, the main storage area of fresh water is very important to understand the input-output freshwater in the Arctic Ocean. The F W C 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 (LSSL) from 2004 to 2007. Results show that the upper ocean in the Canada Basin became continuously fresher from 2003 to 2008, except during 2006. The F W C increased at a rate of more than 1 m · a 1 , and the maximum increase, 7 m, was in the central basin compared between 2003 and 2008. Variability of the F W C was almost entirely limited to the layer above the winter Bering Sea Water (wBSW), below which the F W C remained around 3 m during the study period. Contributors to the F W C 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 apparent impact on the F W C changes. Therefore, this paper focuses on analysis of the latter two factors and the results indicate that they were the major contributors to the F W C variability in the basin.