As a part of the National Report of China for the International Association for Physical Science of Ocean （IAPSO）, the main research results of Chinese scientists in Arctic physical oceanography during 2007-2010 are reviewed in this paper. This period overlaps with the International Polar Year （IPY）, which is a catalyst for nations to emphasize activities and research in the polar regions. The Arctic also experienced a rapid change in sea ice, ocean, and climate during this time. China launched two Arctic cruises with the R/V XUE LONG icebreaker, in 2008 and 2010, which provided more opportunities for Chinese scientists to investigate the Arctic Ocean and its change. During this period, Chinese scientists participated in more than ten other cruises with international collaborations. The main research covered in this paper includes the upper ocean characteristic, ocean and sea ice optics, kinematics of sea ice and the Arctic impact on global climate change. The progress in sea ice optics, the observation technologies and Arctic Oscillation are especially remarkable.
Freshwater content （FWC） 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 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 （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 FWC 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 FWC was almost entirely limited to the layer above the winter Bering Sea Water （wBSW）, 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 apparent impact on the FWC changes. Therefore, this paper focuses on analysis of the latter two factors and the results indicate that they were the major contributors to the FWC variability in the basin.
