Abstract
Near the ocean, the residual circulation in Laguna San Ignacio, located on the Pacific coast of Baja California in Mexico, has been shown to be driven by tides. Here the subtidal circulation in the portion of the lagoon farther from the ocean is shown to be driven by the wind. The pressure difference between two stations, one near the closed end and the other midway along the central axis, is correlated well with the wind stress, in the sense that sea level rises downwind. Where the bathymetry is relatively simple, with a deep channel separating two shoal areas, the flow is upwind at the deepest part of the section, driven by the axial pressure gradient. In areas where the bathymetry is more complex, the direction of the observed flow is parallel neither to the local bathymetry nor to the applied wind stress. Linear theory qualitatively explains the major features of the wind-driven flow, including the relative strength of the pressure gradient to the wind stress, the direction of the flow, and the vertical structure, even in topographically complex areas. The residual circulation, after the wind-driven component has been removed, is assumed to be driven by the salinity gradient. That flow changes direction with depth. Where the bathymetry is simple, the near-bottom flow is toward relatively fresh water; flow is in the opposite direction closer to the surface. A linear model driven by a prescribed horizontal density gradient predicts downgradient flow at all depths near the deepest point of any section—a prediction that is qualitatively different from the observed flow.
Corresponding author address: Clinton D. Winant, Integrative Oceanography Division, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0209. Email: cdw@coast.ucsd.edu
