Mississippi River and Sea Surface Height Effects on Oil Slick Migration

Abstract

Millions of barrels of oil escaped into the Gulf of Mexico (GoM) after the 20 April, 2010 explosion of Deepwater Horizon (DH). Ocean circulation models were used to forecast oil slick migration in the GoM, however such models do not explicitly treat the effects of secondary eddy-slopes or Mississippi River (MR) hydrodynamics. Here we report oil front migration that appears to be driven by sea surface level (SSL) slopes, and identify a previously unreported effect of the MR plume: under conditions of relatively high river discharge and weak winds, a freshwater mound can form around the MR Delta. We performed temporal oil slick position and altimeter analysis, employing both interpolated altimetry data and along-track measurements for coastal applications. The observed freshwater mound appears to have pushed the DH oil slick seaward from the Delta coastline. We provide a physical mechanism for this novel effect of the MR, using a two-layer pressure-driven flow model. Results show how SSL variations can drive a cross-slope migration of surface oil slicks that may reach velocities of order km/day, and confirm a lag time of order 5–10 days between mound formation and slick migration, as observed form the satellite analysis. Incorporating these effects into more complex ocean models will improve forecasts of slick migration for future spills. More generally, large SSL variations at the MR mouth may also affect the dispersal of freshwater, nutrients and sediment associated with the MR plume.

Influence of Mississippi River induced circulation on the Deepwater Horizon oil spill transport

“…Falcini et al . [], using a coastal altimetry based data set, proposed that the DwH oil front migration may be driven by sea surface level slopes; they focused on the Mississippi Delta area. We have examined the broader transport pathways that include the NGoM shelf areas.…”

“…Our results extend the findings in Falcini et al . [], where along track measurements from the Jason‐2 satellite Track 204 were employed to identify an increase in the coastal ADT that was attributed to a strong freshwater mound near the Mississippi Delta in the 25 May to 10 June period. By also employing Track 128, Track 193, and model SSH, we can verify that a similar cross‐shelf sea level difference at the western Delta was the cause of the geostrophic coastal current revealed through our modeled and observed MR plume and SOP distributions.…”

“…It is also a unique topic relating the dynamics of a large-scale river plume with the transport and fate of hydrocarbons. Falcini et al [2012] addressed the impact of the river induced coastal mound at the Mississippi Delta on slick migration during selected dates of the DwH oil spill period. They used satellite altimetry data along one Jason-2 track (204 in Figure 1b) and an idealized two-layer pressure-driven flow model.…”

Bird mortality from the Deepwater Horizon oil spill. II. Carcass sampling and exposure probability in the coastal Gulf of Mexico

“…Response authorities opened locks on Mississippi River canals to redirect the discharge and prevent or delay Deepwater Horizon oil from reaching the ecologically fragile coastal marshes. Under weak winds and effects of sea surface slope, high buoyancy-driven outflow (Falcini et al 2012) blocked much of the surface oil from reaching most Gulf shorelines until late May 2010. Except along the immediate shoreline, wind forcing played a negligible role in large-scale oil transport (Huntley et al 2011) until early July when Tropical Storm Alex transited the southern Gulf (Dietrich et al 2012, Le Hénaff et al 2012.…”

Oil Spill Detection in Glint-Contaminated Near-Infrared MODIS Imagery

“…By collecting the available information on oil spill disasters, such as the Lebanon oil spill (Mediterranean Sea) occurring during the 2006 bombing [12,21] and the Deepwater Horizon drilling rig explosion (Gulf of Mexico, 2010) [8,[22][23][24], and lesser events (e.g., spills released by ships) occurring in the Arabian Gulf [6] and in the Mediterranean Sea [13], we built a fairly large database of in situ oil spill observations. For each of these events, we acquired the corresponding MODIS (AQUA and TERRA) Level 1A passes and retained those in which the spill was well visible and not covered by clouds.…”