Multiple Zonal Jets in a Quasigeostrophic Model of the Antarctic Circumpolar Current

Abstract

The presence of multiple zonal fronts in the Antarctic Circumpolar Current (ACC), a phenomenon described as zonation, has been confirmed by many observations suggesting that the fronts are circumpolar in extent. In the context of quasigeostrophic turbulence models, Panetta has shown that fronts associated with long-lived zonal jets develop spontaneously in very wide baroclinically unstable regions (of width large compared with the Rossby radius of deformation). The present paper examines the relevance of this mechanism to the zonation of the ACC, using a quasigeostrophic wind-forced channel model. Multiple jets appear when the forcing scale is wide enough. and they have horizontal scales and a strength that compares well with observations. However, in the presence of large-scale random topography, a different dynamical regime emerges in which the flow structure depends on the topographically controlled stationary eddies.