Eddy‐Mean Flow Interactions Sustaining the Anomalous Deep Convection Off Prydz Bay in the Subpolar Southern Ocean

Abstract

A remarkable deep‐convection event developed off Prydz Bay in the Indian sector of the Southern Ocean during the austral autumn‐winter of 2017, coinciding with a previously documented anomalous accumulation of eddy kinetic energy. During this event, warm Circumpolar Deep Water (CDW) shoaled toward the upper ocean despite strong surface stratification typically associated with sea‐ice meltwater that suppresses vertical mixing. Using an eddy‐resolving reanalysis data set and an energetics‐based diagnostic framework, we investigate the processes linking atmospheric forcing, eddy variability, and deep convection. The results suggest a dynamic system in which anomalous surface forcing initiates upper‐ocean divergence and preconditioning, followed by intensified mesoscale eddy activity and vertical energy redistribution. These processes together contribute to the development of deep convection and CDW uplift. Enhanced CDW intrusion is accompanied by intensified baroclinic conversion near the continental slope, consistent with eddy growth and enhanced vertical energy convergence. The associated eddy‐mean flow interactions correspond to isopycnal steepening and pronounced southward transport anomalies, producing a zonally asymmetric circulation pattern in the subpolar region. These results highlight that, in addition to atmospheric forcing, energetic eddies play a key role in sustaining vertical exchange and enabling convection to extend to depths approaching 2,000 m. Such intense events can substantially modify regional circulation and water‐mass properties and influence heat and salt redistribution in polar oceans. Understanding these dynamics is essential for improving climate models and predicting future changes in subpolar ocean circulation.