On the secular changes in the tidal constituents in San Francisco Bay

Secular changes up to 7% in amplitude, as well as phase advances of 13 min of time per century in the diurnal and semidiurnal tidal constituents, have been found in previous investigations on the sea level record of San Francisco Bay, California. A numerical hydrodynamic model for barotropic tide is used to explore local causes that may contribute to the secular changes found in the tidal constituents. The results indicate that the morphological evolution of the seabed in the region of the ebb-tidal delta is a major factor that contribute to explain the secular changes observed in the tidal constituents in San Francisco Bay, besides of minor contributions from river flow changes and sea-level rise.