Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


A series of observations of the density distribution across the York River estuary documents distinct lateral differences in density and degree of vertical mixing. The magnitude of the density differences varies throughout the tidal cycle; maximum lateral gradients occur at times of minimum current. When the density distribution is sufficiently inhomogeneous, longitudinal estuarine fronts are generated. These fronts are axially aligned, up to several miles in length, and are apparent for less than 2 hours at any given location. Although the density difference across the frontal boundary is often small, horizontal pressure gradients acting over a broad frontal region generate the convergent circulations necessary to maintain these fronts. Measurements of the longitudinal velocities across the same section reveals negligible phase difference but a significant amplitude difference between the currents in the channel and those over the shoals. Differential advection across the estuary due to this velocity shear is the process by which the observed density distribution is generated.



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