Study On Shelf-Basin Water Exchange In The Pacific Sector Of The Arctic Ocean

Pacific Water is the main carrier of material exchange between the Chukchi Sea and the Canada Basin.Understanding this exchange process is of great help to explore the transport of organic carbon and the expansion of inorganic carbon from the Chukchi Sea to the deep basin.Based on the hindcast simulation in 1996 of a fine resolution ocean-sea ice model(NAPA1/12),the temporal and spatial structures of water masses and circulation in the Pacific sector of the Arctic Ocean are evaluated with observations.The results show that the model can well simulate the main structure of circulation in the study area,and reproduce the characteristics of Pacific Summer Water(PSW)and Pacific Winter Water(PWW)in the Chukchi Sea /Beaufort Sea,as well as the velocity field through key sections from shelf to basin.Further analyses on the distribution of Pacific Water in the four selected sections,namely Bering Strait,Barrow Canyon,Chukchi Slope and Beaufort Slope sections,reveal that PWW remains in the whole year in regions except for Bering Strait.The water mass structures in the four sections suggest that Alaskan Coastal Water(ACW)occupies the most limited area and exists for a smallest duration,while the Newly Ventilated Winter Water(NVWW)and Bering Summer Water(BSW)distribute widely and remain for a long time.Based on the distinct characteristics of temperature and salinity,the pathways of PSW and PWW in the Arctic Ocean are analyzed.PSW is transported in the Chukchi shelf sea in summer and autumn,while PWW is transported in winter and spring.Their pathways are similar and correspond to the three branches of ocean currents in the Chukchi Sea.Most Pacific Water out of Barrow Canyon veers westward at a position varying seasonally,and then separates at the Chukchi Plateau.A certain part of Pacific Water continues to be transported westward,and the majority part enters into the Canada Basin in an anticyclonic direction.In the Canada Basin,PWW locates below PSW and extends more widely.We also find that Pacific Water out of Barrow Canyon can be transported into basin through eddies instead of advection.Barrow Canyon is the main gateway between the Chukchi shelf and deep basin.The warm BSW plays a leading role in the heat flux through Barrow Canyon,and the freshwater flux is mainly contributed by BSW and NVWW.The outflow from Barrow Canyon varies seasonally due to variations in the Pacific inflow through Bering Strait.In the condition with a weak Barrow Canyon outflow,the Pacific Water turns westward along the isobath on the west side of the canyon subjected to the canyon topography.While with the enhanced outflow,the Pacific Water rushes into the southern Canada Basin and then turns westward into Chukchi Slope Current due to the joint effect of slope topography and the Beaufort Gyre.Additionally,the Chukchi Slope Current is "meandering" associated with eddies induced by baroclinic instability.