Potential-Vorticity Characteristics of the Faroe Bank Channel Deep-Water Overflow

Abstract

Results from a 71-day deployment of three ADCP current meters on a section across the sill region of the Faroe Bank Channel are reported. The characteristic density structure of the channel, with warm, highly saline North Atlantic Ocean surface water overlying colder, less-saline deep water originating from the Nordic seas, lends itself well to a two-layer description of flow processes in this region. The dataset has been analyzed to describe the spatial and temporal characteristics of the deep-water potential vorticity. The most striking feature is a persistent cross-channel variation of this quantity, with higher values on the Faroe Bank side. In the 1½-layer hydraulic calculations that were undertaken the potential vorticity was approximated as a linear distribution. The ADCP observations indicated that the deep-water flow was hydraulically controlled, and, using the direct observed transport, the analysis yielded diagnostic results for the upstream reservoir interface level that were in good agreement with observations. It was also concluded that the deviation of the potential vorticity from a constant value had no significant effects on the deep-water transport.