A conceptual model of gravitational circulation and entrapment was developed in the 1970s to help explain the ecological significance of Suisun Bay, a subembayment of San Francisco Bay. New technology developed during the 1980s and 1990s has greatly improved the ability to measure water velocity, salinity, and SSC. Analyses of these data have led to revisions in the conceptual model of gravitational circulation and the estuarine turbidity maximum in Suisun Bay (table 1).
Table 1: Revisions to the conceptual
model of gravitational circulation and
the estuarine turbidity maximum in
Suisun Bay, California [psu, practical
Click on table for a larger version (30 KB)
- Gravitational circulation increases with water depth,
- null zones are geographically fixed,
- gravitational circulation is suppressed by increased vertical mixing during spring tides, and
- the longitudinal salinity gradient, not salinity, drives gravitational circulation.
- Gravitational circulation occurs as near-bottom pulses of landward flow that transport salt, but often little sediment.
- Wind-wave resuspension of bottom sediment in shallow water can affect SSC observed in the deeper channels.
The conceptual model will continue to be improved while continuing to measure and analyze data from Suisun Bay.