Deep Bering Sea Circulation and Variability, 2001-2016, From Argo Data

The mean structure, seasonal cycle, and interannual variability of temperature and salinity are analyzed in the deep Bering Sea basin using Argo profile data collected from 2001 to 2016. Gyre transports are estimated using geostrophic stream function maps of Argo profile data referenced to a 1,000 dbar nondivergent absolute velocity stream function mapped from Argo parking pressure displacement data. Relatively warm and salty water from the North Pacific enters the basin through the Near Strait and passages between Aleutian Islands to the east. This water then flows in a cyclonic (counterclockwise) direction around the region, cooling (and freshening) along its path. Aleutian North Slope Current transports from 0 to 1,890 dbar are estimated at 3-6 Sverdrups (1 Sv=10(6) m(3) s(-1)) eastward, feeding into the northwestward Bering Slope Current with transports of mostly 5-6 Sv. The Kamchatka Current has transports of similar to 6 Sv north of Shirshov Ridge, increasing to 14-16 Sv south of the ridge, where it is augmented by westward flow from Near Strait. Temperature exhibits strong interannual variations in the upper ocean, with warm periods in 2004-2005 and 2015-2016, and cold periods around 2009 and 2012. In contrast, upper ocean salinity generally decreases from 2001 to 2016. As a result of this salinity decrease, the density of the subsurface temperature minimum decreased over this time period, despite more interannual variability in the minimum temperature value. The subsurface temperature maximum also exhibits interannual variability, but with values generally warmer than those previously reported for the 1970s and 1980s.