Influence of Wind Stress Curl and Bottom Topography on the Transport of the Antarctic Circumpolar Current in a Barotropic Perspective

This study investigates the influence of wind curl on the zonal transport and vorticity of a barotropic flow over topography using an idealized quasigeostrophic model. While previous research focuses on how wind stress sets the zonal mean transport over a ridge using idealized models of the Southern Ocean, the interplay between wind curl and constant wind stress in determining zonal transport remains an open question. It is shown that the injection of vorticity through wind curl creates nonzero westward zonal transport, even when there is zero mean wind stress over the domain, which increases with wind curl. The existence of zonal transport is explained qualitatively through differences in zonal dynamics and further studied quantitatively through analytical solutions of governing equations and results obtained from constant wind stress simulations. Our findings additionally suggest that there are two distinct regimes where the zonal transport is determined by wind curl or the mean wind stress when both are present. The first regime is characterized by formation of gyres and Rossby waves whose strengths and amplitudes grow with increasing wind curl, whereas the second regime is described by zonal flow with formation of standing and transient eddies consistent with earlier studies. We determine that the zonal transport and vorticity of the flow are governed by both nonlocal and local mechanisms in the presence of wind stress curl and further explore the interaction between wind curl and topography across a range of ridge heights. The goal of this work is to shed new light on how wind curl influences the dynamics of the Antarctic Circumpolar Current and the eddy saturation regime.