Suspended Sediment Transport in Mississippi Bight during Two Cold Front Events in Spring 2016

O’Brien, S. J., Dykstra, S. L., Parra, S. M., Dzwonkowski, B., Book, J. W., Pan, C., Dinniman, M. S., Fitzpatrick, P. J., Lau, Y. H., Cambazoglu, K., & Wiggert, J. D. (2019). Suspended Sediment Transport in Mississippi Bight during Two Cold Front Events in Spring 2016. 2019 Gulf of Mexico Oil Spill and Ecosystem Conference. New Orleans, LA.

The high frequency (3-7 days) of cold front events in the northern Gulf of Mexico from mid-October to April causes coastal erosion and the transport of suspended sediments to the continental shelf. The interactions between suspended sediments and oil play a key role in the dispersion and degradation of spilled oil, so it is important to understand the sediment transport pathways in this region during cold fronts. Two 600 kHz Acoustic Doppler Current Profilers (ADCPs) were deployed along the CONsortium for oil spill exposure pathways in Coastal River-Dominated Ecosystems (CONCORDE) middle corridor in Mississippi Bight during the Spring 2016 field campaign. A suspended sediment concentration time series was generated from the ADCP’s echo intensity using in situ suspended sediment concentration, temperature, salinity and particle size data. A cold front affected the study area on 1 April and resulted in westerly alongshore and southerly across shore surface currents, and opposite flows in the bottom water at both sites. Suspended sediment concentration of 20 mg/L was present within the water column. A second cold front event on 10 April caused variable alongshore and across shore currents at the surface and at depth, and higher suspended sediment concentration compared to the first cold front. CONCORDE synthesis model’s temperature and salinity, in situ wind and currents suggest the southwesterly Ekman transport of fresh water from Mobile Bay during the post cold front phase was the main cause of the increased suspended sediment concentration observed within the water column.