Eddy‐Mean Flow Interactions and Seasonal Variability of Energetics in the Brazil Current System

Abstract The eddy‐mean flow interactions in western boundary currents are crucial for global ocean heat exchange and energy redistribution. However, to date, the eddy energetics in the Brazil Current (BC) system, one of the three main western boundary currents in the Southern Hemisphere, remains poorly understood. Here we examine the three‐dimensional structure of the eddy‐mean flow interactions and seasonal variability of energetics in the entire BC system. Results show that the BC jet features mixed barotropic‐baroclinic instability along its path (25S–36S), with positive energy cascades enhancing eddy kinetic energy and potential energy. Strong eddy kinetic energy exists in the Brazil‐Malvinas Confluence (BMC) located between 39S and 43S throughout the upper 1,000 m, which is dominated by baroclinic instability, with a clear subsurface maximum. Both the kinetic energy in the BC and the eddy kinetic energy in the BMC show distinct and vertically coherent seasonal variability with minima in winter, and the minimum eddy kinetic energy lags the mean kinetic energy by approximately 2 months. Barotropic and baroclinic conversions with comparable magnitude co‐regulate EKE generation in the BMC, with energetic contributions differing by season and depth, advancing our understanding of eddy‐mean flow interactions in the BC system.