Shelfbreak circulation in the Alaskan Beaufort Sea : mean structure and variability

Abstract

Historical hydrographic and current meter data are used to investigate the properties and circulation at the shelf edge of the Alaskan Beaufort Sea. Thirty-three individual cross-sections, spanning the time period 1950 to 1987, are combined in a topographical framework to produce mean vertical hydrographic sections, as well as a section of mean absolute geostrophic velocity referenced using the current meter data. This reveals the presence of a narrow (order 20 km) eastward current, referred to as the Beaufort shelfbreak jet. The jet has three distinct seasonal configurations: In late-spring to late-summer, cold, winter-transformed Bering water is advected in a subsurface current; from mid-summer to early fall a surface intensified current advects predominantly Bering summer water; and from mid-fall to mid-spring, under easterly winds, the jet transports upwelled Atlantic water. The volume transport of the jet represents a significant fraction of the inflowing transport through Bering Strait. While the characteristics and flow of the winter-transformed Bering water vary interannually, this water mass ventilates predominantly the upper halocline.