Tidally-induced residual currents in Long Island and Block Island Sounds

Abstract

The tidally-induced residual currents in the Long Island Sound-Block Island Sound (LIS-BIS) tidal channel are investigated using a previously-developed analytic model. Known first order tidal properties of LIS-BIS are matched using three different models, chosen to isolate the effects of the factors potentially controlling the second order currents, either breadth, depth or eddy viscosity variations. The residual currents driven by these first order models agree to within roughly a factor of two, indicating that the model is not overly sensitive to these parameters. Tidally-induced currents on the order of observed currents in eastern LIS and BIS are predicted. The outstanding structural feature of the predicted residual currents is a region of strong surface flow divergence and bottom flow convergence centered at a sharp constriction in the channel. Eulerian and Lagrangian observations in eastern LIS and BIS are reviewed; indirect support for the theoretical results is found.