The shadowed island

The circulation of fluid in a basin containing several topographic barriers is considered. Meridional barriers situated east of another barrier "shado w" the western barrier with respect to Rossby wave propagation. The steady circulation responds by reducing the flow through the gaps in the western b arrier. As a consequence, the nature of the recirculation zone described in Pedlosky et al. is strongly affected by the shadowing topography. Generall y, the effect of the shadowing topography is to enhance and enlarge the zon e of recirculation. It is shown that the effectiveness of the shadow depends on whether the eas tern barrier is a peninsula or internal "island." In the latter case, the e ffect of the barrier depends strongly on the relative meridional extents of the two topographic features. In all cases, the peninsula is by far the mo st effective shadowing barrier in reducing the how around the western barri er. Both analytical and laboratory models of the circulation are described. In the former case, the analysis is restricted to linear theory. The laborator y model employs the "sliced cylinder" geometry. Good agreement is found bet ween theory and experiment, although significant alterations are found when the how becomes strongly nonlinear.