Shelf-break exchange in the bering, chukchi and beaufort seas

Abstract

The Bering and Chukchi/Beaufort shelf-breaks form the beginning and end of the dramatic sea-level and wind-forced fl ow of Pacifi c Ocean water across the Bering and Chukchi continental shelves between the Pacifi c and Arctic Oceans. Recent model results suggest that the on-shelf fl ow in the Bering is distributed along the shelf-break, wind-dependant, focused by Zhemchug and Bering canyons and modifi ed by shelf-break eddies. Similarly, the off-shelf fl ow in the Chukchi/Beaufort is mediated by canyons, shelf-break jets, eddies, and wind forcing. In the Chukchi, fl ow is channeled through Barrow and Herald canyons to the shelf-break, where across-slope fl ow in Ekman boundary layers and instabilities result in the exchange of water and properties across the slope. In addition, dense shelf-water, created from brine rejection during ice formation in coastal polynyas, has been observed to fl ow downslope through Barrow Canyon. Along the Beaufort shelf, the shelf-break current is unstable, shedding eddies that populate the deep Beaufort basin. Upwelling favorable winds in summer have been observed to modify the structure of the shelfbreak current and drive exchange across the Chukchi and Beaufort slopes. Most of our understanding of shelf-break fl ow in Bering and Chukchi Seas is based on numerical model results and broad-scale observations. There is thus a need for more detailed shelf-break observational programs.