Dynamics of wind-forced upwelling in the Alaskan Beaufort Sea and associated shelf-basin fluxes

Recent work has demonstrated the frequent occurrence of upwelling along the continental slope of the Alaskan Beaufort Sea, driven by remote Pacific-born storms (Aleutian lows). These events are characterized by an off-shelf flux of surface water and shoreward return flow at depth transporting water from the basin interior onto the shelf. This cross-stream exchange of water, heat, salt, and nutrients can significantly impact both the Beaufort shelf and the interior Canada Basin. However, at this point the dynamics of the upwelling are still uncertain, as is the magnitude of the shelf-basin exchange. Here we use wind data, atmospheric re-analysis fields, shipboard and moored oceanic data, and a simplified ocean numerical model to investigate the dynamics of the upwelling and the nature and magnitude of the cross-stream exchange. We focus primarily on a single storm event that occurred in November 2002 when the region was roughly 50% covered by pack-ice. It was found that the presence of ice enhanced the ocean response to the storm, and that the return flow was not confined to the bottom boundary layer. This is consistent with the momentum balance which includes a significant contribution from the cross-stream advection of alongstream momentum. An analysis of the parcel trajectories during the storm from the model reveals varying patterns across the shelfbreak and continental slope. Flux estimates are made using both the data and the model in order to assess the impact of such wind-driven storm events in the Beaufort Sea.