Study On Hydrological Characteristics And Changes Of Canadian Basin

In recent years,the Arctic environment has undergone rapid changes.As an important part of the Arctic Ocean,the Canada Basin has experienced the most severe decline in sea ice,moreover,changes in its upper ocean have important effects on Arctic sea ice,acoustic fields,ecosystems,and climate.The Canada Basin has always been a key area for Chinese Arctic Scientific explorations,this article systematically analyzes the characteristics of water masses and flow fields in the western and southern part of basin,and focused on the changes in the Pacific water in recent years,using hydrological observation data in the Canadian basin and adjacent waters obtained from previous Chinese Arctic Scientific explorations and international data.The main conclusions are as follows:(1)The upper layer of the Canada Basin and its adjacent waters is mainly affected by the Pacific water,and the middle layer is mainly affected by Atlantic water.The water masses of the Canada Basin mainly include the surface mixing water,the Alaska Coastal Current,the summer Bering Sea Water,the Pacific Winter Water,the Atlantic Intermediate water,deep water and bottom water.The spatial-temporal variation characteristics of water masses are significant,especially in the upper mixed water and the Pacific Water.(2)In the southern part of the Canada Basin,the Pacific water mainly occupies the upper layer above 250m.The depth of the Pacific winter water from the shelf to the basin deepens,and the maximum depth can reach 300m.The Pacific Summer Water has significant spatial variation,with the largest amount of warm water in 2014.Compared with the south part,the western survey area is more stratified,which is more stable in the warm Pacific Water layer,mainly occupying the depth range of 40-80m.It is worth noting that the warm water layer is more stable and warmer in the high-latitude section than in the low-latitude section,especially in the summer of 2016.(3)Since 2012,the Alaska Coastal Current and the summer Bering Sea Water in the basin are getting warmer,the former has larger warming rate.The distribution of Pacific Water in the Canada Basin has significant interannual changes,mainly concentrated in the southwest and middle of the Canada Basin,and the observed northernmost latitude is 800N.(4)The calculation results of geodetic flow show that the flow field in the basin is relatively weak,and the maximum calculation velocity is 300 mm/s.The maximum velocity in the south is near the slope area,and the velocity decreases with the depth of water.The flow field in the western basin is weaker than the south,and the maximum flow velocity is only 110mm/s.Affected by complex terrain,there is flow direction shear near the north wind plain and the north wind ridge,and there are significant vortex affected characteristics in the high-latitude section in 2016.(5)The observation results of the upper layer flow field below the ice in the Canada Basin show that the upper layer flow is relatively weak,with an average flow velocity of 82 mm/s.From the surface to the depth of 80 m,the flow velocity slowly decrease after a certain increase.For the decreasing trend,the maximum flow velocity appeared at 48 m depth below the ice,which was 96 mm/s,and the currents were mainly in the northwest and southeast directions.