Gravitational Circulation in a Tidal Strait

by P. E. Smith, U.S. Geological Survey, Sacramento, United States,
R. T. Cheng, U.S. Geological Survey, Sacramento, United States,
J. R. Burau, U.S. Geological Survey, Sacramento, United States,
M. R. Simpson, U.S. Geological Survey, Sacramento, United States,

Document Type: Proceeding Paper

Part of: Hydraulic Engineering


Eight months of continuous measurements of tidal current profiles with an acoustic Doppler current profiler (ADCP) were made in Carquinez Strait, California, during 1988 for the purpose of estimating long-term variations in vertical profiles of Eulerian residual currents. Salinity stratification near the ADCP deployment site also was analyzed. The strength of density-driven gravitational circulation and the amount of salinity stratification in the strait varied significantly over the spring-neap tidal cycle. Density currents and stratification were greater during neap tides when vertical mixing from the tide is at a minimum. Landward residual currents along the bottom were observed only during neap tides. Simulations made with a three-dimensional model to supplement the field measurements show a significant, tidally induced lateral variation in residual currents across the strait. The Stokes drift of 1-2 cm/s in the strait is small relative to the speed of gravitational currents.

Subject Headings: Tides | Water circulation | Three-dimensional models | Doppler systems | Salinity | Ocean currents | Flow measurement | Fluid flow | California | United States

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