Mysterious flotsam in Gulf came from Deepwater Horizon rig

the Chandeleur Islands retained a weathered red sticker that read “Cuming” with the numbers 75-1059 below it. Reddy found a company called Cuming Corporation in Avon, Massachusetts, which manufactures syntactic foam flotation equipment for the oil and gas industry. He e-mailed photos of the specimen to the company, and within hours, a Cuming engineer confirmed from the serial number that the foam came from a buoyancy module from Deepwater Horizon.

“We realized that the foam and the oil were released into the environment at the same time,” Reddy said. “So we had a unique tracer that was independent of the oil itself to chronicle how oil and debris drifted out from the spill site.”

The scientists overlaid the locations where they found honeycomb debris on 5 and 7 May and 7 with daily forecasts produced by the National Oceanic and Atmospheric Administration (NOAA) of the trajectory of the spreading oil slick. NOAA used a model that incorporated currents and wind speeds, along with data from planes and satellites. On both days, the debris was about 6.2 miles ahead of the spreading slick.

The explanation, the scientists said, is the principle of leeway, a measure of how fast wind or waves push materials. The leeway for fresh oil is 3 to 3.3 percent, but the scientists suspected that “the protruding profile of the buoyant material” acted acting like a sail, allowing wind to drive it faster than and ahead of the floating oil.

In this case, the flotsam served as a harbinger for the oncoming slick, but because different materials can have different leeways, oil spill models may not accurately forecast where oiled debris will head. “Even a small deviation in leeway can, over time, results in significant differences in surface tracks because of typical wind fields,” the scientists wrote.

The Coast Guard has a long history of calculating the leeway of various materials, from life jackets to bodies of various sizes and weights, to improve forecasts of where the materials would drift if a ship sank or a plane crashed into the sea. Calculating leeways, however, has not been standard practice in oil spills.

“We never had solid data to make the case until this study,” said Merv Fingas, who tracked oil spills for more than thirty-eight years for Environment Canada, which is equivalent to the U.S. Environmental Protection Agency.

“These results,” the study’s authors wrote, “provide insights into the fate of debris fields deriving from damaged marine materials and should be incorporated into emergency response efforts and forecasting of coastal impacts during future offshore oil spills.”

This research was funded by the National Science Foundation.

— Read more in Catherine A Carmichael et al., “Floating oil-covered debris from Deepwater Horizon: identification and application,” Environmental Research Letters 7, no. 1 (19 January 2012) ( doi:10.1088/1748-9326/7/1/015301)