Spatio-temporal variability of cross-shelf transport in Mississippi Bight

Mustafa Kemal Cambazoglu, University of Southern Mississippi, Marine Science, Stennis Space Center, MS, United States, Jeremy David Wiggert, The University of Southern Mississippi, Division of Marine Science, Stennis Space Center, United States, Michael S Dinniman, Old Dominion University, Center for Coastal Physical Oceanography, Norfolk, VA, United States and Brandy N Armstrong, USGS, Falmouth, MA, United States
Abstract:
The seasonality and spatial variability of across shelf flow and transport in the Mississippi Bight region of the northern Gulf of Mexico is studied using Coupled-Ocean-Atmosphere-Wave-Sediment Transport (COAWST) modeling system results from 2015 to 2018. Understanding the transport pathways, connectivity and interactions of open waters of the Gulf and coastal/estuarine waters of the Mississippi Bight/Sound is important for studying shelf ecosystem dynamics and management, coastal protection and emergency response in the event of an oil spill, and studying ecosystem functions such as harmful algal bloom dynamics, distribution of different coastal species. A high resolution modeling system was developed and used to support seasonal sampling efforts during the Consortium of oil spill exposure pathways in river dominated ecosystems (CONCORDE) project. This CONCORDE model product is used to identify the spatial and seasonal variations of cross-shelf transport pathways in the study area. A high resolution atmospheric forcing product capturing the diurnal sea-breeze is used to study the resulting circulation and exchange between estuarine and shelf waters in Mississippi Bight. Depth varying across-shelf transport perpendicular to isobaths representing inner-shelf, mid-shelf and outer-shelf boundaries were computed using the results of the 400-m resolution CONCORDE model. Hovmoeller diagrams of transport across the isobaths qualitatively show seasonally recurring onshore transport corridors. A strong NE-SW transport pathway from the Mississippi Bird-foot delta to Mobile Bay’s Main Pass showing connectivity in between the corridors observed on different isobaths was observed. We computed the empirical orthogonal functions (EOFs) of the current variability to study the spatial and temporal variability of across-shelf flow along the water column, to identify the dominant modes of transport at different seasons of the year, and to understand the role of different processes such as wind forcing, tidal forcing and river forcing on the transport pathways. Results also indicate that some of the identified shelf break to nearshore transport pathways follow the bathymetry on the shelf.
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