Modeling studies of mesoscale circulation in the Gulf of California

The mesoscale circulation in the Gulf of California is investigated using a numerical model (Princeton Ocean Model). Forced by satellite-derived winds, the circulation in the gulf shows a complex pattern dominated in the southern gulf by multiple eddies. Near the coast and in most of the north gulf, the circulation is wind-driven. Away from the coast, velocity fluctuations are poorly correlated with the wind. Positive relative vorticity at the surface seems to be produced along the west side and to extend into the interior in the vicinity of cyclonic eddies. Negative vorticity values are significant near anticyclonic eddies and seem to be connected to the east coast. Regions of relatively high values of turbulent kinetic energy ½q 2 (≈10−4cm2s −2) are found in the interior away from the boundary layers at depths 350–500 m and are associated with low values of the Richardson number, negative relative vorticity and concentrations of near-inertial wave energy. In a separate set of experiments the evolution of remotely forced coastal-trapped waves in the gulf is studied. In general, model-data sea level and velocity fluctuations are reasonably well correlated. Coastal-trapped waves propagate northward along the east side of the gulf with no significant changes south of the sill. Most of the wave energy is steered at the sill to the west side of the gulf where it propagates southward with decreased sea level amplitude. Just a small fraction of the wave energy enters the northern gulf and is dissipated. Some of the incident wave energy is lost into down-slope propagating disturbances generated as the CTWs pass resulting in relatively intense bottom currents. Wave disturbances exhibit nonlinear characteristics while propagating. Most of the dissipation of wave energy in the gulf takes place through bottom friction in the vicinity of the sill. On the east side, large amplitude elevation waves produce a down-gulf current adjacent to the coast such that the up-gulf currents associated with the wave separate from the coast. Eddies with a spatial scale of 50–80 km are generated by long time scale or large amplitude waves.