Impact of Diurnal Sea Breeze on Planktonic Dynamics and Hypoxia Onset in the Mississippi Bight

Wiggert, J. D., Pan, C., Dinniman, M., Lau, Y. H., Fitzpatrick, P. J., O'Brien, S., Bouchard, C., Cambazoglu, M., & Hofmann, E. (2018). Impact of Diurnal Sea Breeze on Planktonic Dynamics and Hypoxia Onset in the Mississippi Bight. 2018 American Geophysical Union Fall Meeting. Washington, DC.

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. 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. The circulation model was spun-up and forced using oceanographic initial and lateral boundary conditions provided by a 1-km resolution regional implementation of the Navy Coastal Ocean Model (NCOM) in the Gulf of Mexico. The biogeochemical module includes multiple planktonic and particulate size classes, and explicitly tracks dissolved oxygen with benthic cycling interaction. The sediment transport module provides insight into how suspended sediments impact the in situ light field (and therefore phytoplankton growth rates). 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 was deployed by the CONCORDE (Consortium for oil spill exposure pathways in Coastal River-Dominated Ecosystems) research program, which was established to investigate seasonal variations of the complex fine-scale biological, chemical and physical interactions in a marine system controlled by pulsed-river plume dynamics. The highly resolved exchanges between nearshore lagoonal estuarine waters and the adjacent continental shelf provide new insight into how seasonal variation of hydrologic and atmospheric forcing influences ecosystem function in the highly productive waters of the Northern Gulf of Mexico. Twin experiments, implemented through application of a low-passed realization of the high resolution atmospheric forcing, are performed to examine how the region’s prevalent diurnal sea breeze impacts estuarine exchange, planktonic distribution, hypoxia onset and biogeochemical cycling.