Evolution of the Loop Current System During the Deepwater Horizon Oil Spill Event as Observed with Drifters and Satellites

Abstract

The ocean circulation patterns of the Gulf of Mexico (GOM) Loop Current (LC) system and their effects on the advection of the oil discharged during the Deepwater Horizon incident are described using in situ surface drifter trajectories and satellite observations from May to August 2010. These observations include altimetry-derived surface geostrophic velocities, sea surface temperature, ocean color, and surface oil locations. The elongated, northwestward penetrating LC retreated back from its northernmost position in late April 2010 and stayed farther away from the surface oil in the north during May 2010. Although the main body of the surface oil slick remained around the well site and on the Northern Gulf shelf, a small amount of the surface oil was entrained into the northern part of the LC system in mid-May 2010. An anticyclonic eddy in its formative stage then detached from the northern part of the LC in the latter part of May 2010, tending to break the direct connection between the northern Gulf with points farther south. Through interactions with smaller cyclonic eddies on either side, multiple short-lived detachment/re-attachment episodes continued for some time during the spill event, but without ever fully reestablishing a direct LC pathway from the region of the oil spill to the Florida Straits. The mean geostrophic current pattern during this time period showed a separated LC eddy in the eastern GOM. Such ocean circulation patterns helped retain the surface oil in the northeastern Gulf and kept an oil-free environment for most of Florida's coastal waters.