Pacific Water Transport in the Western Arctic Ocean Simulated by an Eddy-Resolving Coupled Sea Ice–Ocean Model

Abstract

Abstract The process of the Pacific water transport in the Chukchi Sea and the southern Canada Basin is investigated by using an eddy-resolving coupled sea ice–ocean model. The simulation result demonstrates that the Pacific water flows into the basin by mesoscale baroclinic eddies, which are generated and developed as a result of the instability of a narrow and intense jet through the Barrow Canyon. Each eddy has a baroclinic anticyclonic structure, and its horizontal and vertical scales grow up by being merged with other ones during August and September, they separate into anticyclones whose diameters are about 50 km in October, and then they gradually shrink in early winter. The Pacific water transport across the Beaufort shelf break reaches maximum (about 0.3 Sv, where 1 Sv ≡ 106 m3 s−1) during late summer and early autumn when the eddy activities are enhanced. The sensitivity experiments indicate that the shelf-to-basin transport differs depending on the sea ice condition in the Chukchi Sea during summer. The difference is found to be associated with the jet strength, which is closely related to the location of the sea ice margin. When the sea ice margin is located in the Canada Basin, the jet is stronger, and mesoscale eddy activities and corresponding inflow of the Pacific water into the basin are enhanced. When sea ice remains in the shelf even in late summer, sea ice ocean stress plays a great role in braking the jet and the consequent suppression of the shelf-to-basin transport. The freshwater and heat transports into the basin associated with the Pacific water inflow depend on not only the volume flux but also on surface buoyancy flux in the shelf, which varies according to sea ice condition. The freshwater transport referenced to 34.8 psu is 259 km3 yr−1 in the medium sea ice extent case. Although the Pacific water becomes freshened as a result of its mixing with sea ice meltwater in the large extent case, the freshwater transport is still less than in the other cases. The heat transport is promoted by preferable absorption of solar heat in addition to energetic eddy-induced transport in the small extent case. The heat amount provided into the basin is equivalent to the reduction of sea ice thickness by about 1 m yr−1 north of the Chukchi and Beaufort shelf breaks.