Internal Tide Generation at the Vitória‐Trindade Ridge, South Atlantic Ocean

• Published in: Journal of geophysical research. Oceans 2018-08, Vol.123 (8), p.5150-5159
• Main Authors: Paiva, Afonso M., Daher, Victor B., Costa, Vladimir S., Camargo, Simone S. B., Mill, Guilherme N., Gabioux, Mariela, Alvarenga, João B. R.
• Format: Article
• Language: English
• Subjects: Baroclinic mode; baroclinic tides; Beams (radiation); Continental margins; Energy; Fluxes; Fourier analysis; Geophysics; Harmonic analysis; Height; Internal tide generation; Internal tides; internal waves; Missions; Oceans; Plane waves; Satellite altimetry; Satellites; Sea surface; Seamounts; Temperature (air-sea); Tidal dynamics; Tides; Wave propagation; Wavelengths; western South Atlantic
• ISSN: 2169-9275; 2169-9291
• DOI: 10.1029/2017JC013725

Sea surface height data from multiple satellite altimetric missions are analyzed in order to investigate the surface manifestation of internal tides generated at the Vitória‐Trindade Ridge (VTR), in the western South Atlantic Ocean. The VTR is formed by a sequence of submerged seamounts disposed in a west‐east alignment around 20.5°S, extending for over 1,000 km from the Brazilian continental margin to the Trindade and Martim Vaz islands. Point‐wise harmonic analysis of the along‐track sea surface height data, combined with a two‐dimensional plane wave fitting at selected subregions, depicts well‐organized northbound and southbound wave beams radiating from the VTR, and propagating as far as ~1,000 km from the ridge. Energy convergence is observed at a focal point located circa 300 km south of the VTR, associated with a lens effect due to the arc‐shaped ridge. Wavenumber spectra show highest energy associated with wavelengths of 140 and 70 km, close to the theoretical values expected for the first and second baroclinic modes, respectively. Energy fluxes for the mode 1 principal lunar (M2) constituent reach values of 2 to 3 kW/m for the southward beams and 1 kW/m north of the VTR. Judging from its surface signature, the VTR appears to be the most significant internal tide generation site in the western South Atlantic. Key Points Altimeter data reveal the Vitória‐Trindade Ridge as the main generation site of internal tides in the western South Atlantic Energy fluxes radiating from the ridge reach levels similar to those of other important generation sites in the world ocean The energy fluxes converge to a focal point located to the south of the ridge due to a lens effect, further radiating southward