Numerical simulation of M₂ internal tides in the South Brazil Bight and their interaction with the Brazil Current

Abstract

[1] A fully three-dimensional nonlinear primitive equation ocean model is applied to study the semidiurnal internal tide in the South Brazil Bight under summer conditions. Along the shelf break and upper slope of this region, the upper layer (0-600 m) is occupied by the southward flowing Brazil Current. Several numerical experiments were conducted to investigate the generation and propagation of the M 2 internal tide. Using horizontally homogeneous and vertically stratified density fields, internal tides were generated over the whole Bight with a clear signal on the continental shelf. When a more realistic summer stratification was considered, a baroclinic jet, representative of the Brazil Current, developed and comparisons between current observations and modeled results were improved. This jet acts as a barrier to the coastward propagation of the internal tide generated over the slope, reflecting it back towards the open ocean. On the negative relative vorticity side of the Brazil Current, located over the shelf, internal tides are trapped, enhancing vertical current variability and, hence, tidally induced mixing. The results highlight the importance of considering background flows when investigating internal tides in regions of strong along-slope baroclinic flows such as western boundary currents.

From regional to local scale modelling on the south-eastern Brazilian shelf: case study of Paranaguá estuarine system

“…The Brazil current also induces shelf break upwelling, which is reinforced by wind driven upwelling in the summer (CAMPOS et al, 1995;CAMPOS et al, 2000). Furthermore, internal waves are generated over the shelf break and slope (PEREIRA; CASTRO, 2007a;PEREIRA et al, 2007b).…”

Hydrography and currents on the Pernambuco Continental Shelf

“…Some studies analyzing the Brazilian continental shelf have been conducted mainly on its southeast and south regions (EMÍLSSON, 1961;MIRANDA, 1985;CARVALHO;RIBAS, 1998;PEREIRA et al, 2007;MOLLER JUNIOR et al, 2008;HILLE;RIBEIRO, 2008, among others). Nevertheless, research on the northeast and north regions are scarcer, e.g., Geyer et al (1996) in the area off the mouth of the Amazon River (Para and Amazonas states) and Dias, Castro and Lacerda (2013) in the region of the mouth of the Jagaribe River (Ceara state).…”

A Regional Study of the Brazilian Shelf/Slope Circulation (13◦-31◦s) Using Climatological Open Boundaries

“…They showed that M 2 and S 2 height components induce almost uni-directional SE-NW counter-clockwise ellipses of currents. A numerical tidal study in the South Brazil Bight by Pereira et al (2007) explained that the M 2 tide phase is influenced by the existence of two amphidromic points located in the South Atlantic.…”