Where Did the Deepwater Horizon Spill's Oil Go? The Contaminated Deep Ocean

The 2010 Deepwater Horizon spill in the Gulf of Mexico was one of the worst spills in history. Yet there's an unsolved puzzle when it comes to this spill: the location of the two million barrels of submerged oil thought to be trapped in the deep ocean. Now, scientists have taken a closer look at the path that the oil followed in order to discover its location.

In order to find the location of the oil, the scientists used data from the Natural Resource Damage Assessment process conducted by the National Oceanic and Atmospheric Administration. They analyzed data from more than 3,000 samples collected at 534 locations over 12 expeditions.

So what did they find? They discovered a 1,250-square-mile patch of the deep sea floor where there was 2 to 16 percent of the discharged oil. The fallout of oil to the sea floor created thin deposits most intensive to the southwest of the Macondo well.

"Based on the evidence, our findings suggest that these deposits come from Macondo oil that was first suspended in the deep ocean and then settled to the sea floor without ever reaching the ocean surface," said David Valentine, one of the researchers, in a news release. "The pattern is like a shadow of the tiny oil droplets that were initially trapped at ocean depths around 3,500 feet and pushed around by the deep currents. Some combination of chemistry, biology and physics ultimately caused those droplets to rain down another 1,000 feet to rest on the sea floor."

In fact, the researchers identified hotspots of oil fallout close to damaged deep-sea corals. This supports previous findings that these corals were damaged by the oil spill.

"These findings should be useful for assessing the damage caused by the Deepwater Horizon spill as well as planning future studies to further define the extent and nature of the contamination," said Valentine. "Our work can also help to assess the fate of reactive hydrocarbons, test models of oil's behavior in the ocean and plan for future spills."

The findings are published in the journal Proceedings of the National Academy of Sciences.