Can the Intermediate Western Boundary Current recirculation trigger the Vitória Eddy formation?

South of the Vitória-Trindade Ridge, a seamount chain off East Brazil, Brazil Current (BC) meanders cyclonically within Tubarão Bight, occasionally forming Vitória Eddy. It was recently found that Intermediate Western Boundary (IWBC), which flows equatorward below BC, recirculate Bight. We present an analysis AVISO observations suggest Eddy formation is conditioned by strength BC upstream A weak prone to local meandering and eddy in bight, while strong suppresses bight but triggers downstream meander growth. To study effects IWBC recirculation on formation, we formulate simple two-layer quasi-geostrophic model. In model, represented meridional jet upper layer steady lower layer. The lower-layer effectively acts as topographic bump, affecting upper-layer via stretching term \(\psi _{2}/{R_{d}^{2}}\), where ψ2 streamfunction Rd baroclinic deformation radius. Based sea-surface height data previous observational studies, define stationary reference jet. conduct number initial-value problem experiments varying speed. slowly develops cyclone above eddy. As increase velocity, faster larger. But too-strong has opposite effect: potential vorticity anomalies induced are quickly swept away, leading explosive growth; no formed all cases, initial trigger linear process (the steering eddy). even when weak, nonlinearity becomes important, dominating dynamics after 10 days simulation. growth fully nonlinear. Our idealized QG model confirms can elucidates mechanisms involved this process.