Continuously stratified flow dynamics over a hollow

Abstract

To study the effects of bathymétrie depressions (hollows) on continuously stratified flows, measurements of current velocity and water density profiles were obtained over two hollows in the lower Chesapeake Bay. Measurements snowed an acceleration of the middepth flow as it moved toward the deepest part of the hollow, in contrast to the deceleration expected from two-dimensional Bernoulli-type dynamics. The acceleration was attributed to lateral water intrusions that were most apparent during floods, as corroborated by observations in a transverse section that crossed the deepest part of one of the hollows. The flow acceleration toward the deepest part of the hollows during flood, favored by lateral water intrusions, was deflected toward the right (looking landward) owing to Coriolis accelerations. In general, during ebb and flood, the dynamics over the hollows could be explained with three-dimensional Bernoulli-type dynamics (pressure gradient balanced by advection) modified by Coriolis acceleration. Outside the hollows, the dynamics were between pressure gradient and friction (stress divergence). The transition from frictionally dominated dynamics (outside the hollow) to advectiondominated dynamics (inside the hollow) appears at the region where the bathymetrie slope equals the bottom drag coefficient. Copyright 2009 by the American Geophysical Union.