Impact of Wind Stress Curl on the Eddy Saturation of the Antarctic Circumpolar Current from a Barotropic Perspective

Abstract

Eddy saturation, a phenomenon where east-west transport remains insensitive to changes in wind stress, is believed to play a crucial role in explaining the behavior of the Antarctic Circumpolar Current (ACC). Two distinct mechanisms are known to lead to eddy saturation: (i) baroclinic instability in stratified flows and (ii) topographic-barotropic instability in unstratified flows. This study focuses on eddy saturation resulting from topographic-barotropic instability in a doubly periodic domain. Previous findings have shown that topographic-barotropic instability, typically occurring within a specific range of wind stress, is significantly influenced by the geometry of the topography. We investigate how the introduction of wind stress curl affects the occurrence and the dynamics of eddy saturation. Our findings demonstrate that wind stress curl and its interaction with topography is crucial in understanding the eddy saturation and, consequently, for determining the zonal transport of the ACC. In the doubly periodic domain, a dependence is observed between the zonal transport and the wind stress variations in relation to mean wind stress,  associated with the form stress composed by the interaction with bottom topography with singular and multiple ridges.