Geostrophic Pumping, Inflows and Upwelling in Barrier Reefs

Abstract

Abstract The communication between shallow and deep oceans via gaps in the separating barrier reefs is examined using a simplified two-layer analytical model. Attention is focused on the flow resulting from a sea-level difference between the ocean and the lagoon. Such a difference imposes a pressure gradient along the gap which, in turn, forces a flow into the lagoon. The coral reefs, which extend all the way to the surface and are exposed to the atmosphere at low tide, are presented by two portions of an infinitely long wall. A group of passages, whose combined width is not very small compared to the Rossby radius, is represented by a single gap separating the two portions of the wall. The fully nonlinear model is inviscid, hydrostatic and nondiffusive. Nonlinearity is essential because (i) the flow in the passages is rather fast, and (ii) the depth variations are of order unity. Steady solutions for the upstream and downstream fields are constructed analytically using the momentum equation in an integra...