A Modeling Study of Coastal-Trapped Wave Propagation in the Gulf of California. Part II: Response to Idealized Forcing

Abstract

The propagation of incident coastal-trapped waves in the Gulf of California is investigated using a hydrostatic primitive equation model. The behavior of idealized incident wave disturbances with different amplitudes and time scales is examined. The incident wave disturbances propagate northward up-gulf along the east side with no significant change. At the sill, which is 600 km north of the entrance, the wave splits and most of the energy is steered to the west side where it propagates southward down-gulf with decreased amplitude (50%). A small fraction (10%?20%) of the incident energy enters the north where it is dissipated. Sea level at the entrance of the gulf is well correlated with sea level everywhere inside the gulf. In contrast, correlations of depth-averaged velocity between Topolobampo (close to the entrance of the gulf) and locations around the gulf decrease along the propagation path of the wave. Most of the dissipation of wave energy in the gulf takes place through bottom friction in the vicinity of the sill. Incident waves with large, but realistic, sea level displacement magnitudes exhibit nonlinear properties. Phase speeds increase as the sea level displacements of the incident waves increase from ?30 to +30 cm. Waves of sea level elevation steepen. 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. The separation process seems to be connected with subsequent downslope propagation of energy. Energetic anticyclonic eddies with spatial scales of 50?80 km can be generated by long-time-scale or large-amplitude elevation waves.