The Atlantic Water Boundary Current in the Chukchi Borderland and southern Canada Basin

Numerous studies over the past decade have enhanced our understanding of the Pacific Water boundary current system in the western Arctic Ocean, including the Beaufort Shelfbreak Jet and Chukchi Slope Current. However, relatively little is known about the flow of Atlantic Water in this part of the Arctic Ocean, including its path, structure, and transport. Here we use a collection of high-resolution shipboard crossings of the Atlantic Water boundary current (AWBC) in the southern Canada Basin, spanning the time period 2003-2018, together with historical hydrographic data over a broader region to quantify aspects of the AWBC. The 9 repeat crossings reveal the presence of two eastward-flowing AWBC branches: one at the base of the continental slope and one farther offshore in the Canada Basin. Each branch is identifiable by temperature and velocity. The transport of the inner branch is 0.18 Sv, and that of the outer branch is 0.33 Sv, where the upper boundary is the 27.06 kg/m3 isopycnal corresponding to the Pacific/Atlantic interface, and the lower boundary is 800 m. The temperature cores of the two branches vary in phase with each other, but there is no apparent relationship to the velocity. Using temperature-salinity signatures, the historical data were used to determine how the AWBC navigates the Chukchi Borderland to form the two branches observed in the southern Canada Basin. The propagation of interannual warm anomalies of Atlantic Water via the current system is addressed as well.