Curvature and Meanders of the Antarctic Circumpolar Current

The ACC is the only circumpolar current in the global ocean, yet its behavior is far more complex than a simple zonally re-entrant current that is often used to model the leading order dynamics of the flow. As a result of interactions with topography and surface forcing, the ACC exhibits meanders over a range of scales from a broad southward drift occurring over much of the Indian and Pacific sectors to sharper standing meanders found in the lee of topographic features. In this talk we consider the impact of these standing meanders on setting global properties of the ACC using a realistic, eddy-resolving ocean GCM. We focus on two aspects: (i) the correlation between transient fluctuations in the size and structure of standing meander regions with eddy fluxes of momentum and buoyancy and (ii) the modification of eddy diffusivities across the standing meanders. In the former case we find that variations in the spatial extent as well as the curvature of standing meanders are likely to play a significant role in the equilibration of the ACC's mean flow. In the latter case we specifically consider the divergent component of the eddy fluxes to show that suppression of eddy diffusivities by the mean flow is strongly modified by local meandering and strong curvature.