A numerical study of dense water outflows and halocline anticyclones in an arctic baroclinic slope current

Abstract

We examine the relation between the dense water migration from the shelf to the deep ocean and offshore generation of halocline anticyclones in a physical setting appropriate for an Arctic baroclinic current system, using a nonhydrostatic numerical ocean model. The model basin contains an outer shelf connected to the deep sea by a continental slope. The ocean is cyclical in the alongshore direction. Sea surface is frictional to account for the ice‐exerted friction. A series of inflows and outflows is imposed on the shoreward side of the shelf to facilitate the release of dense waters into the basin. The distribution of inflow‐outflow is sinusoidal in the alongshore direction. Inflow carries dense water into the basin while the outflow withdraws ambient shelf water from the shelf. The multiple sources produce an array of dense plumes entering the shelf. Seaward migration of dense plumes is examined with and without an offshore baroclinic current bounded to the left by the shelf. The baroclinic current, if present, is supported by slanted isopycnals rising toward the shelf break. Without the baroclinic current, downslope sinking plumes veer to the right and produce an undercurrent trapped by the continental slope. With the baroclinic current, convection along slanted isopycnals can divert dense plumes away from boundary trapping and produce intense subsurface anticyclones offshore. Initial meanders embedded in the baroclinic current can trigger instabilities and also produce subsurface anticyclones offshore. However, disturbances induced by sinking plumes and instabilities of offshore origin generally do not interact constructively to intensify subsurface anticyclones offshore.