Observations of Internal Tides at the Vitória-Trindade Ridge, South Atlantic Ocean

Abstract

The Vitória-Trindade Ridge (VTR) has been shown, based on satellite altimetry, to be an important region for the generation of internal tides (ITs) that radiate southward and northward into the South Atlantic Ocean. Here, nearly 1 year of unprecedented high-density in situ velocity and temperature data collected at this undersampled region, were used to investigate and quantify the IT properties and variability. About 90% of the total tidal energy can be accounted for by the IT in the semidiurnal band. The data depict a dominant surface-intensified mode-1 vertical structure associated with progressive baroclinic waves, with a less prominent mode-2 growing in importance from January to June. Values of energy conversion from the barotropic to the baroclinic semidiurnal tides are comparable to other important sites of IT generation in the world ocean. Energy conversion and the highly coherent energy fluxes are strongly related with the spring-neap cycle, indicative that the observed IT are predominantly generated at the observational site. Fluxes and conversion are modulated by significant changes in the vertical stratification of the upper ocean, which are observed to occur during the different months of observations.