The Rio Grande Rise circulation: Dynamics of an internal tide conversion hotspot in the Southwestern Atlantic

Abstract

The Rio Grande Rise (RGR) is a plateau located at 31°S in the Southwestern Atlantic, rising from 5916 m up to 161 m below the sea level. The RGR is an important site for future mining of Fe-Mn crusts and can lead to an expansion of Brazil’s Exclusive Economic Zone. The Cruzeiro do Sul Rift (CSR) fault cuts through the RGR from southeast to northwest. In this study we characterize the RGR circulation, showing that M2 tides are the main source of variability in the region, with an amplitude that can reach 0.3 m s⁻¹, larger than the mean flow. These M2 tides are dominated by the baroclinic component and intensified near the bottom. The generation of M2 internal tides occurs mainly in the CSR slopes, with most energy converted from the barotropic tide being radiated away in the form of tidal beams. In addition, the impingement of the mean southern South Equatorial Current and tidal rectification generates anticyclonic circulations around the RGR peaks, with the latter mechanism being responsible for a bottom intensified anticyclonic circulation of 0.2 m s⁻¹. Finally, our results reveal that the RGR is a hotspot of internal tide generation in the Southwestern Atlantic.