The Sedimentation and Lateral Transport of Oil-Associated Marine Snow During and After the Deepwater Horizon Oil Spill

The sedimentation of oil-associated marine snow (MOS) was shown to be an important pathway by which Deepwater Horizon (DWH) oil was removed from the water column. Here, we (1) estimate the vertical and lateral transport of marine snow and MOS particles based on the physical environment in the NE Gulf of Mexico (NEGoM) during and after the DWH oil spill and (2) characterize the impacts of interannual environmental variability on particle fluxes during summer 2010, 2011, and 2013. The physical environment was simulated using the Connectivity Modeling System (Paris et al. 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, which retained and aggregated particles and likely enhanced MOS sedimentation. 2011 did not show strong distinguishing circulation features. Particles originated from both the east and the west sides of the study area and advection occurred primarily along bathymetric lines or via smaller mesoscale eddies present in the NEGoM. Forward simulations suggested that particles with high sinking rates (200 m d^-1) reached the seafloor within < 5 to 15 days, depending on the depth. Particles with high sinking rates also 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 or sediment when water masses came into contact with the seafloor along the shelf slope.