Currents and transport on the Eastern Bering Sea shelf: An integration of over 20 years of data

More than 20 years of data from moorings, satellite-tracked drifters and hydrographic surveys are integrated to provide a comprehensive view of currents and transport on the eastern Bering Sea shelf. The major sources of water onto the eastern Bering Sea shelf are North Pacific water flowing through Unimak Pass and Bering Slope water flowing onto the shelf usually via the canyons that intersect the shelf break. Absolute geostrophic transport through Unimak Pass varies from an average of 0.25×106m3s−1 (Sv) in the warm months to 0.43Sv in the cold months. Flow along the 50-m isobath is weak, with a transport of <0.1Sv (calculated from current meters) in summer and fall. The transport along the 100-m isobath measured at two locations is more than twice that along 50-m isobaths; in the summer at the Pribilof Islands it was 0.2Sv and during spring and summer at 60°N the northward geostrophic transport (referenced to the bottom) was 0.31Sv. Northward transport along the 100-m and 50-m isobaths accounts for approximately half of the transport through Bering Strait. A typical transit time from Unimak Pass to Bering Strait is >13 months and from Amukta Pass to Bering Strait via the Bering Slope Current is >8 months. Consequently, the source of most of the heat transported into the Arctic through Bering Strait is a result of air–sea interactions local to the northern Bering Sea. Analysis of the currents and water properties on the southern shelf indicates that ~50% of the shelf water is exchanged with slope water during October–January each year. This exchange elevates the October mid-shelf average nitrate level from 6μM to 14–16μM by the end of January.