Topographically Generated Submesoscale Shear Instabilities Associated with Brazil Current Meanders

Abstract The western boundary current system off southeastern Brazil is composed of the poleward-flowing Current (BC) in upper 300 m and equatorward flowing Intermediate Western Boundary (IWBC) underneath it, forming a first-baroclinic mode structure mean. Between 22° 23°S, BC-IWBC jet develops recurrent cyclonic meanders that grow quasi-stationarily via baroclinic instability, though their triggering mechanisms are not yet well understood. Our study, thus, aims to propose mechanism could initiate formation these mesoscale eddies by adding submesoscale component hydrodynamic scenario. To address this, we perform regional 1/50° (∼2 km) resolution numerical simulation using CROCO (Coastal Regional Ocean Community model). results indicate incoming anticyclones reach slope upstream separation regions generate barotropic instability can trigger meanders’ formation. Subsequently, this process generates cyclones contribute, along with growth, resulting submesoscale-to-mesoscale inverse cascade. Last, as grow, they interact slope, generating inertially symmetrically unstable anticyclonic vortices filaments. Significance Statement Off Brazil, meanders. Such enhance open-ocean primary productivity societal importance located region rich oil gas where oil-spill accidents have already happened. This study explore processes responsible for eddies. We find instabilities eject filaments show topographically generated play an important role dynamics Brazil. Moreover, may resolving operational models contribute increase predictability