2026/07/27 by Alexis Johnson Exley, Kathleen Donohue, Xiaobiao Xu
paper · doi:10.1175/jpo-d-25-0073.1
Abstract Regions of elevated eddy kinetic energy (EKE) downstream from topographic ridge systems of the Southern Ocean are analogous to atmospheric storm tracks. Typically investigated using a three-dimensional wave activity flux framework, the dynamics of storm tracks are primarily governed by energy transfers between the mean and eddy fields. Here, 3 years of high-resolution numerical model output is used to diagnose these eddy–mean field interactions and the physical mechanisms responsible for initiating and maintaining the Southeast Indian Ridge storm track in the Southern Ocean. Background dynamics are found to be primarily governed by the vertical wave activity flux divergences, corresponding to the baroclinic conversion of energy. This term suggests ubiquitous baroclinic growth across the domain but is largely enhanced in the crest of the standing meander. While baroclinic instability remains a nonnegligible contributor, temporal variability in array-averaged EKE is found to be associated with the horizontal wave activity flux terms, corresponding to the barotropic conversion of energy and a mixed instability regime. This variability is event driven and, when decomposed into synoptic storm-track case studies, shown to be analogous to atmospheric downstream development. Anomalously, large local increases in EKE are attributed to an extremely extended meander, which obstructs the typical propagation of these barotropic perturbations. These major events are compared to an atmospheric omega block and hypothesized to significantly increase eddy heat and tracer fluxes and therefore play a sizable role in the eddy-driven arm of the Southern Ocean overturning circulation.