Southern Ocean Storm Tracks via Flow-Topography Interactions

Eddy kinetic energy (EKE) varies by an order of magnitude or more along the path of the Antarctic Circumpolar Current (ACC). In the atmosphere, storm tracks are regions of enhanced EKE in the midlatitudes that arise through localized orographic and energetic forcing. Despite these similarities, few studies have compared the formation and maintenance of atmospheric and oceanic storm tracks. We use an idealized primitive equation channel model of the ACC to investigate the localization of EKE in an oceanic regime. Compared to previous studies, we run simulations in a very long channel that allows for a large separation between regions of enhanced and suppressed EKE. We find that flow interactions with topography generate standing meanders that have spatial scales distinct from mesoscale eddies. Interactions of the flow's zonal mean component with its meandering component lead to longitudinally zonal variations in EKE through enhanced localized convergence and divergence of heat. We show that the length scale of these oceans storm tracks depends on the magnitude of the surface wind stress implying that changes in surface wind patterns are be able to alter the patterns of EKE in the Southern Ocean. The focus of this study on local time-averaged transient and standing eddy fluxes provides insights into the dynamical structure of the Southern Ocean that is not apparent from traditional zonal or along-stream averages.