The effects of channels and shoals on exchange between the Chesapeake Bay and the adjacent ocean

The role of bathymetric changes in determining the transport of water and salt in the lower Chesapeake Bay (LCB) was investigated using high-resolution acoustic Doppler current profiler (ADCP) and conductivity-temperature-depth profiles. A cross channel transect was repeated eight times during neap tides on October 6-7, 1993, which illustrated the lateral structure of the longitudinal and transverse flow fields and the intratidal variations in the flow structure across the LCB. Amplitude and phase of the M2 tidal component, as well as the mean flow velocity, were calculated using least squares fitting at every point of a uniform grid obtained from the ADCP data. The results differ from the classical two-layer pattern of estuarine circulation modified by Coriolis effects but are consistent with recent hydrographic observations. The authors propose a possible explanation for the observed flow and density structure as follows: the barotropic and baroclinic forcing interact with the bathymetry to extend the inflow from the bottom to the surface, thereby inducing a transverse circulation that yields near-surface convergence over the channels. (from Authors)