By Dan Zak
Washington Post Staff Writer
Tuesday, June 8, 2010; 4:19 PM
ABOARD THE THOMAS JEFFERSON -- Halfway through its 10-day mission to hunt for underwater oil in the Gulf of Mexico, this survey vessel of the National Oceanic and Atmospheric Administration has found erratic, moving clouds of hydrocarbons -- which may be oil and gas -- at depths of more than 3,600 feet less than eight nautical miles from the site of the BP oil spill, officials said Tuesday.
The clouds are about 330 feet in height and fill in another piece of the underwater puzzle that various agencies and universities have been assembling over the past month.
As the Thomas Jefferson cruised nine nautical miles off Grand Isle, La., Tuesday morning, Shepard M. Smith, the ship's commanding officer, said the data collected so far would suggest "a cloud of oil droplets rather than a continuous river," or plume, emanating directly from a single source. The hydrocarbons were discovered 7.5 miles west-southwest of the spill site, where a well blowout 5,000 feet below the gulf's surface caused a massive explosion and fire April 20 aboard the Deepwater Horizon drilling rig, which sank two days later.
Water samples from the area of the subsurface clouds must be analyzed to determine whether the hydrocarbons are from the leaking BP well or from a cluster of observed natural seeps near the survey site.
The ability to map the underwater presence and movement of oil is an unsettled science, according to onboard experts, who are employing a quickly assembled grab bag of equipment and methods in a vanguard attempt to plot the behavior of deepwater oil.
So far, they have found that the subsurface hydrocarbon clouds are loose and flowing unpredictably, appearing in one spot and then vanishing a day later. This, combined with the unknown origin of the anomalies, makes conclusions scarce at this point, according to crew member Larry A. Mayer, director for the Center for Coastal and Ocean Mapping at the University of New Hampshire.
"It's a cat-and-mouse game," said Mayer. "What we're looking at is the long-term fate of spilled oil. The surface presence is measurable. The real unknown is what is happening in the deep sea, and I think that will be unknown for a long time."
Other scientists, who say they have no doubt about the existence of a plume or plumes, have reached more concrete conclusions. The latest came Tuesday morning from Samantha Joye, a professor of marine sciences at the University of Georgia who returned Sunday from a two-week research expedition coordinated by the National Science Foundation.
"There is strong evidence that the plume does derive from the Deepwater Horizon," said Joye. She said she has "never seen concentrations of methane this high anywhere" in the 15 years she has worked in the Gulf of Mexico, suggesting that natural seepage is not a factor.
"The feature was strongest near the Deepwater Horizon spill site, and decreases as you move away from the spill site," she said.
The University of Georgia-led team of scientists tracked the plume from three-quarters of a mile to nearly 14 miles from the damaged BP wellhead.
In Washington, NOAA Administrator Jane Lubchenco announced that the agency's Weatherbird II research vessel has found subsurface oil at three sites, but in low concentrations of less than 0.5 parts per million.
"NOAA is confirming the presence of very low concentrations of subsurface oil, at sampling depths ranging from the surface to 3,300 feet, at locations 40 and 42 nautical miles northeast of the well site and another sampling station at 142 nautical miles southeast of the wellhead," Lubchenco told reporters.
She said that based on "fingerprinting" of the oil, the samples taken 40 nautical miles northeast of the wellhead appeared to be from the BP oil spill. The samples taken 42 miles from the wellhead did not contain enough oil to do fingerprinting, while the oil found 142 miles southeast of the Deepwater Horizon site was not consistent with the BP spill, Lubchenco said.
She said scientists must still analyze data from other vessels, including the Thomas Jefferson, that are still out on the water or returning from cruises.
"We remain concerned about the location of oil on the surface and under the sea," Lubchenco said. "We will continue to do research to understand where it is and in what concentrations and what impact it will have."
She added: "There's definitely oil there. It's in low concentrations. That does not mean it doesn't have significant impact. The impact that it has, we remain to understand."
Staff writer William Branigin in Washington contributed to this report.