Submesoscale Phenomena Due to the Brazil Current Crossing of the Vitória Trindade Ridge
Abstract
At 20.5°S, the Brazil Current and the Intermediate Western Boundary Current interact with a quasi zonal seamount chain, the Vitória Trindade Ridge (VTR). While the mesoscale variability generated due to these western boundary currents crossing the VTR has been recently studied, the submesoscale dynamics associated with such features have never been addressed. Here, we use new observations and a 2 km resolution model to analyze the role of the VTR seamounts in the regional submesoscale dynamics, their seasonality, and instabilities. We present new high resolution velocity and density observations that capture submesoscale features associated with the flow. Within these regions, potential vorticity (PV) reveals patches of symmetrically unstable flow close to seamounts. The horizontal resolution (Δx ≃ 1.5 km) of our quasi synoptic observations (10 h) partially resolves submesoscale instabilities. Our Regional Oceanic Modeling System simulation identifies two regimes of submesoscale activity in the region, one typically associated with the seasonal cycle of the mixed layer, and a second associated with flow-topography interactions. A spatiotemporal analysis of the vertical buoyancy fluxes points to these flow-topography interactions as the main source of recurrent, deeper instabilities. As the VTR emerges as a submesoscale hotspot in the oligotrophic South Atlantic, the lack of observations still remains the main obstacle to better understand submesoscale processes in the region.
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JGR Oceans - 2020 - Napolitano - Submesoscale Phenomena Due to the Brazil Current Crossing of the Vit ria%E2%80%90Trindade Ridge.pdf (14.38 Mo)
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