18. Physical Processes Influencing the Sedimentation and Lateral Transport of MOSSFA in the NE Gulf of Mexico

Accurate predictions of the transport and fate of oil spilled in the marine environment are essential for response and mitigation efforts. The sedimentation of oil-associated marine snow (MOS) has been shown to be an important pathway by which Deepwater Horizon (DWH) oil was removed from the water column; thus, information is needed on the vertical and lateral dispersion of MOS. Here, we simulated the physical environment in the NE Gulf of Mexico using the Connectivity Modeling System (Paris et al., Environ Model Softw 42:47–54, 2013). Field measurements of marine snow provided initial conditions for the simulations. High Mississippi River (MR) discharge during 2010 and 2013 resulted in strong eastward flowing fronts along the shelf break to the east of the MR, and an anticyclonic eddy at the shelf break retained and aggregated particles, which acted to enhance MOS sedimentation. Forward simulations suggested that particles with high sinking rates (200 m d⁻¹⁾ reached the seafloor within <5–15 days and settled within 0–30 km of their origin, while particles with low sinking rates (30 m d⁻¹) were dispersed up to 110 km away from their origin. Suspended particles (no sedimentation rate) may be transported over 300 km from their origin.