CONVERGENT FRONTS IN THE CIRCULATION OF TIDAL ESTUARIES
1986; Elsevier BV; Linguagem: Inglês
10.1016/b978-0-12-761890-6.50013-7
AutoresJohn H. Simpson, William R. Turrell,
Tópico(s)Marine and environmental studies
ResumoThe interaction of tidal flow with freshwater buoyancy input produces a variety of frontal structures in estuaries. These fronts are important, not only as indicators of significant circulation mechanisms, but also as rather specialized features of the estuarine regime in which strong convergence and sinking lead to the concentration of buoyant material, surface-active components and swimming organisms. In estuaries where tidal flow is limited, the freshwater outflow forms a buoyant layer that spreads on the surface as a density current with a plume front at the leading edge. Strong flood tide currents may force the plume front back into the estuary to produce a tidal intrusion front whose movement within the estuary may be explained in terms of density current dynamics. This type of front exhibits a characteristic V configuration with an isolated point convergence at the apex and an associated gyre system. In still more vigorous tidal flows the estuary becomes well-mixed and the density current structure breaks down. In these circumstances the vertical and lateral shear in the flood current may interact with the longitudinal density gradient to produce a transverse circulation with an intense convergence along the axis of the tidal flow. A diagnostic model has been used to determine the form and amplitude of this circulation but still requires direct validation. An improved method for the quasi-synoptic measurement of the transverse velocity field is described. Initial results confirm the existence of full-depth transverse circulation cells in the flow.
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