2023 CSDMS meeting-043
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A coupled benthic-pelagic biogeochemical model for estimating sediment-water exchange of particulates and solutes: sensitivity tests and application to the northern Gulf of Mexico
Dongxiao Yin,
Virginia Institute of Marine Science Gloucester Point Virginia, United States. dyin@vims.edu
Linlin Cui, Virginia Institute of Marine Science Gloucester Point Virginia, United States. lcui@vims.edu
Courtney Harris, Virginia Institute of Marine Science Gloucester Point Virginia, United States. ckharris@vims.edu
Kanchan Maiti, Louisiana State University Baton Rouge Louisiana, United States. kmaiti@lsu.edu
Hannah Beck, Louisiana State University Baton Rouge Louisiana, United States. hdye1@lsu.edu
Julia Moriarty, University of Colorado Boulder Boulder Colorado, United States. Julia.Moriarty@colorado.edu
The sediment bed and the water column are tightly coupled in shallow water systems including large portions of the continental shelf. For instance, the continental shelf seafloor receives ~48% of the global flux of organic carbon to the seabed and the shelf benthic flux serves as a key source of nutrients for sustaining marine life. Observational studies of sediment-water exchange require concurrent measurements in both compartments; however, these are difficult to obtain and rarely available. Numerical modelling provides a valuable alternative approach to observational studies, however many previous modeling efforts used simple sediment-water parameterizations that did not capture the nonlinearities of benthic-pelagic coupling. Here, we present a coupled benthic-pelagic model that includes realistic representations of biogeochemical reactions in both compartments, and the fluxes at the interface. The model is built on the modeling algorithms for sediment-water exchange in ROMS and expanded to include carbonate chemistry and anerobic reactions in the seabed. The updated model is tested for three sites where benthic flux and porewater concentration measurements are available in the northern Gulf of Mexico summer hypoxic zone. Model-data comparison demonstrates the robustness of the calibrated model in reproducing the porewater concentration-depth profiles of O2, DIC, TA, NO3 and NH4, as well as the benthic fluxes of the former three. Further sensitivity experiments reveal that labile material input, bio-diffusion intensity and anerobic mineralization pathways are the three major factors regulating the benthic fluxes and porewater concentrations of O2, DIC and TA. To conclude, our model results provide important insights into the variation of sediment-water exchange under different environmental conditions. This model has the potential to be used as a research and management tool to quantify the role of shelf sediment in driving bottom water hypoxia and acidification over continental shelves.
