Abstract: Since the 1990s, the Arctic marine environment has entered a period of rapid change characterized by a significant reduction of sea ice. Here, we examined changes in the upper ocean of the Canada Basin during this period. Temperature and salinity profile data were obtained from four mooring systems of the Beaufort Gyre Exploration Project, which were deployed in the Canada Basin from 2003 to 2011. These data were used to analyze the characteristics of intermediate Atlantic Water in the Canada Basin. During the period of observation, the Atlantic Water core temperature remained steady in the central Canada Basin, decreased significantly on the Chukchi Plateau, and increased continuously to the north of the central basin region and the Canadian Archipelago slope break. The corresponding Atlantic Water core depths increased to different extents, and was primarily influenced by different surface fresh water contents and changes of wind stress due to melting sea ice. The surface heat content (75—200 m depth) of the four stations increased significantly in ice-free areas, while remaining stable in sea ice areas. Heat content changes at 200—400 m and 400—800 m depths are consistent with the changes of the Atlantic water core depth. When the Atlantic water core depth reached 400 m or greater, the heat content decreased between 200—400 m and increased between 400—800 m. Although the four stations are all located in the Canada Basin, the mechanisms responsible for the changes of the intermediate Atlantic Water differ to each other.

Key words: Canada basin, Intermediate Atlantic water, Core temperature and depth, Fresh water content, Heat content