Simulations of underwater plumes of dissolved oil in the Gulf of Mexico

Abstract

A simple model of the temperature‐dependent biological decay of dissolved oil is embedded in an ocean‐climate model and used to simulate underwater plumes of dissolved and suspended oil originating from a point source in the northern Gulf of Mexico, with an upper‐bound supply rate estimated from the contemporary analysis of the Deepwater Horizon blowout. The behavior of plumes at different depths is found to be determined by the combination of sheared current strength and the vertical profile of decay rate. For all plume scenarios, toxic levels of dissolved oil remain confined to the northern Gulf of Mexico, and abate within weeks after the spill stops. An estimate of oxygen consumption due to microbial oxidation of hydrocarbons suggests that a deep plume of hydrocarbons could lead to localized regions of prolonged hypoxia near the source, but only when oxidation of methane is included.

Response to Comment on “A Persistent Oxygen Anomaly Reveals the Fate of Spilled Methane in the Deep Gulf of Mexico”

“…Although the peak rate constant produced by the model was slightly higher than previously published values (19), this small difference is as expected given the much higher initial methane concentrations in the DWH output (4,7). Notably, a more sophisticated oil-spill model prior to our work (20) incorporated the published rate constant (19) with which our modeled rates agree most closely.…”

Deepwater Horizon Oil Spill: A Review of the Planktonic Response

“…Use of dispersant can expedite the removal of oil from the water column by increasing the rate of biodegradation by bacteria (Venosa and Holder, 2007 (Valentine et al, 2010). Models of oxygen depletion due to bacterial respiration predicted hypoxia would occur within a few hundred kilometer radius of the wellhead at depths greater than 1,000 m (Adcroft et al, 2010). Though measurements showed oxygen drawdown, there was no evidence of hypoxia (Kessler et al, 2011).…”

Evidence of lasting impact of the Deepwater Horizon oil spill on a deep Gulf of Mexico coral community

“…However, because the observed impact was patchy within many colonies (Figure 2), we consider it more likely that this variability reflected an uneven dispersion of the impacting agent in the water. If oil, dispersant, or a combination of the two were present as droplets (Adcroft et al, 2010;Paris et al, 2012) rather than dissolved when an underwater plume from the Macondo Well reached this aggregation of corals, the impact could have been patchy. Similarly, if the impact was in the form of toxic material adherent to particulate organic material or "marine snow" raining down from above (National Commission on the BP Deepwater Horizon Oil Spill and Offshore Drilling 2011; Passow et al, 2012), then this form of delivery could also account for the patchy pattern of impact observed.…”