Wave-driven circulation and transport in a tropical barrier reef system in the western Caribbean Sea with a phase-resolving model

This study investigates wave-driven circulation and transport in a tropical barrier reef system in the western Caribbean Sea using a nested modeling framework. Realistic offshore wave conditions are downscaled with a basin-scale phase-averaged (SWAN) model and used to force a high-resolution, phase-resolving, non-hydrostatic model (SWASH). The phase-resolving simulations explicitly capture the nonlinear wave transformation, wave breaking, and the resulting setup and wave–current interactions from the fore-reef to the lagoon. The depth-averaged momentum balance analysis shows that cross- and alongshore terms are of similar magnitude and are primarily governed by the radiation stress gradients, pressure gradients, and bottom friction. Alongshore momentum and circulation arise from the combined effects of wave incidence angle, local changes in bathymetry alongshore, and spatial variations in setup. The circulation patterns are intrinsically two-dimensional, with energetic circulation cells and water exchanges with the open sea occurring through gaps in the reef crest. Transport timescale estimates show rapid flushing over the reef flat and much slower renewal in the lagoon, highlighting the critical role of geomorphic complexity and wave conditions in controlling water retention and potential exposure to stressors in reef systems.