Influence of River Inputs and Diurnal Sea Breeze on the Tidal Inlet Exchanges that control the Marine Ecosystem and Biogeochemical Processes of the Mississippi Sound and Bight

A circulation model based on the Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) Modeling System, with coupled biogeochemical and sediment transport modules, has been implemented for the Mississippi Bight and the adjacent estuarine waters of the Mississippi Sound. The model has 400-m horizontal resolution, 24 vertical layers, was forced with observed riverine inflows, and includes wetting/drying capability to resolve shallow inshore regions. A 1-km, hourly resolution regional atmospheric forcing product that accounts for diurnal sea breeze impacts has been developed and applied. Model experiments focus on periods when comprehensive ship-based sampling of the complex fine-scale biological, chemical and physical interactions is available in this marine system that is controlled by pulsed river plume dynamics. Highly resolved exchanges between nearshore lagoonal estuarine waters and the adjacent continental shelf provide new insight into how hydrologic and atmospheric forcing influences ecosystem function and biogeochemical cycling in the highly productive waters of the Northern Gulf of Mexico. Twin experiments, implemented through application of a low-passed temporally filtered realization of the high-resolution atmospheric forcing, are performed to examine how the region’s prevalent diurnal sea breeze impacts estuarine exchange, water quality, planktonic and larval advection, hypoxia onset and intensity, and pathways of submarine groundwater discharge. Detailed insight into how shore to shelf connectivity influences these processes is revealed through dye and drifter release experiments.