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Scientists fish for the elusive ghost of the Deepwater Horizon

NOAA joins the hunt for the cloud-like mass of potentially damaging subsurface oil believed to be from the Deepwater Horizon disaster.

June 09, 2010|By Jim Tankersley

Reporting from the Gulf of Mexico — Early on the morning of June 5, the scientists on this federal research ship saw a ghost. Its faint white silhouette appeared on their computer screens, glimpsed at a depth of 1,100 meters by a sophisticated sonar device.

The Thomas Jefferson motored on.

Thirty hours later, the ship returned to that spot in the Gulf of Mexico, seven and a half miles west-southwest of the runaway deepwater oil leak. This time, the ghost was gone.

It was the most instructive encounter yet between researchers and what some federal officials have dubbed "the Loch Ness Plume" — an apparently large and elusive mass of hydrocarbons roaming the deep sea, with potentially devastating consequences for marine life for months, even years, to come.

The appearance and disappearance of the oil helped convince the scientists the plume was not so much a plume. Instead, it appeared to act like a cloud, forming and dissolving in the deep currents.

"Whatever it is," Larry Mayer, a University of New Hampshire professor and ocean researcher who joined the government's search for the undersea oil this week, "it is something that is variable in space and time."

This is to say, still a bit of a mystery.

At a minimum, more than half a million barrels of oil have flowed into the gulf since BP's Deepwater Horizon drilling rig exploded April 20, leaving 11 men dead. Skimmers and controlled burns have removed some of the oil, but vast slicks coat the ocean surface.

Scientists — first from the University of South Florida, now joined by the government — are racing to find it, to study it and to help block it before it washes ashore.

A few clues have fallen into place. The National Oceanic and Atmospheric Administration announced Tuesday that its tests had confirmed the existence of broad areas of subsurface oil as far as 142 nautical miles from the leak source, in depths from 50 meters to 1,400 meters. The concentration of the oil was low, and only some of it could be definitively linked to the Deepwater Horizon.

Aboard the Thomas Jefferson, the search for details has transformed the 208-foot ocean-floor-mapping vessel into a high-tech fishing boat trolling for oil instead of red snapper.

Before the ship set sail from Galveston, Texas, last week, commanding officer Lt. Denise Gruccio wound wire onto winches until 4 a.m. She and her crew bought every ounce of Dawn dish soap on the shelves at a local Home Depot to pour into steel tubs onboard for improvised oil-cleaning stations. They secured two refrigerators on the starboard deck with a wide yellow strap to keep water samples cool.

They also loaded special equipment onto the ship, including three tools for hunting plume: a revolver-style collection of water-sampling tubes, a traditional and time-consuming option; a sophisticated sonar device, which works like a souped-up fish finder from a bass boat; and a steel-gray canister dubbed "the fish," which scans the shallows and depths for oil using florescent imaging.

The Thomas Jefferson crew pioneered the idea to use all the tools in concert.

"The ability to map underwater oil is far from settled science," said NOAA ship Cmdr. Shepard M. Smith, who on Tuesday briefed a small group of reporters on the methods. "There's no great body of knowledge about how this will work."

Yet the results from the ship's first few days at sea proved encouraging. Crew members cast the so-called fish into deep and shallow waters 172 times in the first three days. Crew members poured the water samples from the deep waters into plastic bottles.

Mayer and colleagues including Alex De Robertis, a fisheries biologist and sonar expert, built computer maps of areas where the fish canister and the other sensors detected oil.

Only lab tests of their water samples will confirm that the oil clouds they identified are linked to the Deepwater Horizon. It will be a few more days before anyone can gauge the success of their just-started shallow-water effort, which could help responders predict the underwater drift of oil.

The Thomas Jefferson will sail a few more days, then return to port for water and other supplies. It might revert to its role as a mapping vessel. Or it might go back for another round of ghost hunting.

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