Tracking Subsurface Oil in the Aftermath of the Deepwater Horizon Well Blowout, 2010-04-20, 2011-03-22.

The flow of oil and other hydrocarbons from the ruptured Deepwater Horizon wellhead posed a tracking problem not only for the oil that reached the surface, but also for the hydrocarbon compounds that remained at depth. By applying an existing nowcast/forecast model for the ocean circulation of the eastern Gulf of Mexico, we were able to respond immediately to this tracking need. Our approach was based on advection. We did not attempt to include thermodynamic considerations because there were too many unknowns. Instead, we assumed that some compounds would reach certain levels and be carried three dimensionally by the currents there. Without a priori knowledge, we deployed virtual drifters at depth of 1400, 1200, 100, 800, 600, 400, 200, 100 m and at the surface, and to mimic the continuous flow of oil, we added new virtual particles every 3 h from 20 April 2010, when the rig exploded, to July 15 2010, when the ruptured wellhead was capped. We then continued tracking these virtual particles until 22 March 2011 when almost all of the virtual drifters were found to have exited the model domain. Our results are in qualitative agreement with the limited observations and inferences of subsurface hydrocarbon locations obtained by ship surveys made through the spill. Our work was also used to successfully inform some of these cruises on where to look for subsurface hydrocarbons. Our findings are discussed and comments are provided for becoming better environmental stwards of the coastal ocean going forward. This dataset is associated with the publication Weisberg, R.H., L.Y. Zheng, and Y. Liu (2011), Tracking subsurface oil in the aftermath of the Deepwater Horizon well blowout, Geophys. Monogr. Ser., 205-215, doi: 10.1029/2011GM001131.