UH simulation charts BP oil spill path

Researchers at the University of Hawaii at Manoa’s School of Ocean and Earth Science and Technology (SOEST) have created a simulation of the effects of the BP Gulf oil disaster 360 days after the spill, in order to help guide research and recovery efforts. The simulation assumes that the spill is capped by September 17, and that it has been spewing 50,000 barrels per day. PCmag reports.

These animations show the spread of the oil spill from the Deepwater Horizon rig over one year. They were created from a series of computer simulations by a team of researchers at the School of Ocean and Earth Science and Technology, University of Hawaii at Manoa: Fabian Schloesser from the Department of Oceanography, Axel Timmermann and Oliver Elison Timm from the International Pacific Research Center Hawaii.

For the simulations, 5 million buoyant particles were released continuously from April 20 to September 17, 2010, at the location of the Deepwater Horizon oil rig. The release occurred in ocean flow data from simulations conducted with the high-resolution Ocean General Circulation Model for the Earth Simulator (OFES). The paths of the particles were calculated over 360 days from the beginning of the spill. The simulations were conducted with surface ocean circulation data of 5 typical years rather than the actual flow fields. The dispersal of the particles does not capture such effects as oil coagulation, formation of tar balls, chemical dispersion and microbial degradation. Computed surface concentrations relative to the actual spill may therefore be overestimated. The simulation, thus, is not a detailed, specific prediction, but rather a scenario that could help guide research and mitigation efforts.

The animations show the calculated surface particle concentrations for grid boxes about 10-km-by-10-km in size into April 2011. For an estimated flow of oil from the Deepwater Horizon well of 50,000 barrels per day over a 150 day period, a concentration of e.g. 10 particles per a grid box corresponds roughly to an oil volume of 2 m3 per ~100 km2 area. The animations show the initial spreading of oil into the Gulf of Mexico followed by its entry from the Loop Current into the narrow Florida Current and then the Gulf Stream. Transported by the Gulf Stream, the erratic paths of the particles in the Atlantic are due to strong current instabilities associated with ocean eddies and recirculations. This leads to a high degree of particle dispersal and dilution in the open Atlantic away from the coast.

These computer simulations suggest that the coastlines near the Carolinas, Georgia and Northern Florida could see the effects of the oil spill as early as October 2010. The main branch of the subtropical gyre is likely to transport the oil film towards Europe, although strongly diluted. Furthermore, the animations show that as the northeasterly winds intensify near Florida around October and November, the oil in the Atlantic moves closer to the eastern shores of the US, whereas it retreats from the western shores of Florida. These changes are due to a balance between wind forcing of ocean currents and the Coriolis effect.

The animations furthermore suggest that the narrow, deep Straits of Florida force the Florida Current into a narrow channel, creating a tight bottleneck for the spreading of oil into the Atlantic. After one year, about 20% of the particles initially released at the Deepwater Horizon location had been transported through the Straits of Florida into the open Atlantic according to an averaging over the 5 different years of typical ocean surface current data. The animations suggest that a filtering system in the narrowest spot of the Florida Current could mitigate the spreading of the oil film into the North Atlantic.