|M2 currents and residual flow in the Gulf of California|
Quirós, G.; Badan-Dangon, A.; Ripa, P. (1992). M2 currents and residual flow in the Gulf of California. Neth. J. Sea Res. 28(4): 251-259
In: Netherlands Journal of Sea Research. Netherlands Institute for Sea Research (NIOZ): Groningen; Den Burg. ISSN 0077-7579, more
|Authors|| || Top |
- Quirós, G.
- Badan-Dangon, A.
- Ripa, P.
The full nonlinear, vertically-averaged equations of motion are time integrated through a finite difference scheme on a regular grid that reproduces the topography of the Gulf of California with a mesh size of 14 km. The model is forced through a remote, open-ocean boundary to the south by a linear superposition of the incoming and outgoing Kelvin waves of the M2 tide. Friction, parameterized by a quadratic depth-dependent law, and a viscosity close to 103.m²·s-1, suffice to stabilize the model. The resulting maps of tidal elevations and phase agree adequately with those drawn by other authors from coastal observations. The computed tidal flows are dominated by the effects of the large bathymetric gradients; the currents accelerate markedly in the narrows and straits around the Gulf's large islands, and effects of resonance and bottom friction are evident in the shallow northern Gulf. An average of the computed flow over an integral number of tidal cycles yields a residual circulation with typical values two orders of magnitude smaller than those of the instantaneous flow, organized in basin-wide closed cells with adjacent gyres rotating in opposite senses. The largest cell is a counterclockwise gyre found in the northern Gulf, which is probably driven by a transfer of tidal vorticity to the mean field through a bottom frictional torque. Residual flows are also important in the region of the large islands where the rectification is induced by the large topographic gradients in the channels and sills. The M2 residual circulation should remove a passive tracer from the upper Gulf in several months, or close to one year. No appreciable residual effects of the M2 tide are observed in the southern part of the Gulf.