Topographic Modulation of the Wind Stress Impact on Eddy Activity in the Southern Ocean

Abstract

Previous studies proposed that the increase in the eddy kinetic energy (EKE) in the Southern Ocean in recent decades is primarily caused by the strengthening of circumpolar surface westerlies. However, the spatial pattern of EKE change does not match the pattern of wind change. Here, we revisit the relationship between EKE and wind stress through an observational analysis and model experiments and show that the change in EKE is primarily determined by the mean flow. The increasing wind stress intensifies the circumpolar mean flow contributing to increasing EKE; yet strong EKE variations are generally confined downstream of major topographic features. This arises from the releasing of available potential energy as the mean flow passes through the topography. Our results indicate that the change in Southern Ocean eddy activity has a distinct localization characteristic due to the strong dynamical influence of topography.