Abstract:

Pacific water exits the Chukchi Sea shelf through Barrow Canyon in the east and Herald Canyon in the west,forming an eastward-directed shelfbreak boundary current that flows into the Beaufort Sea. Here we summarize the transformation that the Pacific water undergoes in the two canyons,and describe the characteristics and variability of the resulting sbelfbreak jet, using recently collected summertime hydrographic data and a year-long mooring data set. In both canyons the northward-flowing Pacific winter water switches from the western to the eastern flank of the canyon, interacting with the northward-flowing summer water. In Barrow canyon the vorticity structure of the current is altered, while in Herald canyon a new water mass mode is created. In both instances hydraulic effects are believed to be partly responsible for the observed changes.The shelfbreak jet that forms from the canyon outflows has distinct seasonal configurations,from a bottom-intensified flow carrying cold, dense Pacific water in spring, to a surface-intensified current advecting warm, buoyant water in summer.The current also varies significantly on short timescales, from less than a day to a week. In fall and winter much of this mesoscale variability is driven by storm events, whose easterly winds reverse the current and cause upwelling. Different types of eddies are spawned from the current, which are characterized here using hydrographic and satellite data.

Key words: Chukchi Sea, Arctic Ocean, outflow of Pacific water