Topographically-generated submesoscale shear instabilities associated with Brazil Current meanders

• Ano de defesa: 2022
• Autor(a) principal: Luko, Caique Dias
• Tipo de documento: Dissertação
• Tipo de acesso: Acesso aberto
• Idioma: eng
• Instituição de defesa: Biblioteca Digitais de Teses e Dissertações da USP
• Palavras-chave em Português: Barotropic Instability; Brazil Current; Cape Frio Cyclone; Cape São Tomé Cyclone; Cascata Inversa; Ciclone de Cabo de São Tomé; Ciclone de Cabo Frio; Corrente do Brasil; Instabilidade Barotrópica; Inverse cascade; Submesoscale Coherent Vortices; Vórtices Coerentes de Submesoescala
• Link de acesso: https://www.teses.usp.br/teses/disponiveis/21/21135/tde-22092022-151013/

Off southeastern Brazil, a unique first-mode-like baroclinic jet is observed above the continental slope: the southward flowing Brazil Current (BC) which occupies the upper 200-300 m, and the northward flowing Intermediate Western Boundary Current (IWBC) which spans from ~200-300 m to ~1800 m. Between 22° and 23°S, the BC-IWBC jet develops recurrent cyclonic meanders that grow quasi-stationarily via baroclinic instability. Such meanders enhance the open-ocean primary productivity and are of societal importance as they are located in a region rich in oil and gas where oil-spill accidents have already happened. Here, we aim to further explore the processes responsible for triggering the formation of these mesoscale eddies by adding the submesoscale component to the hydrodynamic scenario. To address this, a 2-km resolution numerical simulation is performed with CROCO. Our results indicate that incoming anticyclones reach the slope upstream of separation regions and generate submesoscale barotropic shear instability that trigger the meanders\' formation. Subsequently, this process generates submesoscale cyclones that contribute, along with baroclinic instability, to the meanders\' growth resulting in a submesoscale-mesoscale inverse cascade. Lastly, as the mesoscale cyclones grow, they interact with the slope generating anticyclonic submesoscale vortices and filaments that are inertially and symmetrically unstable.