Residual circulation and tidal stress in the Gulf of California -: art. no. 3317

Results of a three-dimensional nonlinear barotropic shelf model are used to study the effect of the M-2 tidal stress on the residual current in the Gulf of California. The tidal stress summarizes the nonlinear interactions and forces the residual circulation. It is calculated following the method developed by Nihoul and Ronday [1975]. The vertical structure of the tidal stress reveals clearly the zones where the interaction between tidal currents and the basin geometry is strong. The highest values of tidal stress were found over the Salsipuedes sill and in the Ballenas Channel in the central archipelago and in the Colorado River Delta. Relatively high values of tidal stress were also found in deeper layers in the southern part. The high tidal stress values coincide well with the anomalous cold-water patches observed in the archipelago area, attributed to tidal mixing. The calculated residual currents show a maximum of about 15 cm s(-1) in the upper layers in the archipelago area. At subsurface layers an anticyclonic circulation is observed. Divergence patterns in the upper layers suggest that M-2 tide residuals contribute, to significant upward movements of water, on the west side of Tiburon island. This barotropic process may contribute to the generation of the observed cold patches.