BOSTON, Sep 2, 2010 (Tierramérica) - Stealthy submarine gliders slide through the depths of the Gulf of Mexico with the precision of birds of prey. Robot-like rovers search for droplets of oil thousands of metres under the surface. Powerful computerised analysers send instant results to scientists on board the ship above. All of this to assess the impact of disaster.
The specialised equipment, ordinarily used to measure the number of plankton suspended in ocean water, or to search for hydrothermal vents on the ocean floor, is now being used to study the fate of the five million barrels of petroleum (about 758 million litres) that spilled into the Gulf after the Deepwater rig exploded Apr. 20.
That day the Deepwater Horizon platform, leased by the multinational British Petroleum (BP), suffered an explosion, and then sank on Apr. 22. It was not until Jul. 15 that the gushing leak could be stopped.
The U.S. National Science Foundation has so far funded 60 Gulf research projects, totalling 7 million dollars. BP has proposed spending 500 million dollars on Gulf research over 10 years.
A scientific team from the Woods Hole Oceanographic Institute (WHOI), near the northeastern U.S. city of Boston, has already been to the Gulf and back, and come away with "millions" of points of data to analyse, WHOI oceanographer Chris Reddy told Tierramérica.
"We want to know how much oil spilled, what was the status of the oil at a given point in time, and how it changes as it gets older," he said
The team relied heavily on Sentry, their newest automated underwater vehicle. Programmable via computer, the bright yellow, square-shaped Sentry does not need to be tethered to a ship and dives to 4.3 kilometres below the surface, "until it finds oil, like a dog after bone," Reddy said.
In mid-June, Sentry travelled from Boston to the Gulf of Mexico, where the WHOI crew loaded it aboard the research vessel Endeavor and set sail for a 12-day mission.
Sentry's main purpose was to search for plumes of oil. Lead scientist Rich Camilli equipped Sentry with a tiny mass spectrometer (used to measure and analyze molecular compounds), adapted to work deep underwater.
The crew programmed the underwater vehicle to "sniff around" in the water until it located the highest concentrations of oil and take samples, sending the results back to Reddy, on board the Endeavor.
Reddy used the results from the mass spectrometer to determine the Deepwater Horizon crude's unique "genetic" fingerprint, the characteristics that set it apart from other loose oil in the Gulf, an area of intense petroleum exploitation.
"Crude oil is old plant material that has been cooked and squeezed in the earth," Reddy said. Oil is made up of different compounds, and they are present in different ratios, depending on the origin of the oil. Scientists can test for these ratios in samples of oil.
"I exploit those properties as a scientist," Reddy said. "I can tell, for example, that there's been a lot of evaporation of oil," due to the warm Gulf water, the hot summer temperature and the wind, he added.
Oil changes over time, and that, too, can be analysed. Some compounds break down easily in the water, others evaporate, while still others are resistant and tend to persist in the form of "tar balls."
"It's environmental forensics," Reddy said.
This enabled the team to determine where the Deepwater oil moved on the surface and in plumes thousands of meters under the water. Reddy analyzed oil that coated a marsh on the Louisiana coast 80 kilometres from the wellhead: "I could see the Deepwater fingerprint and that it had already undergone significant evaporation."
Before the Endeavor set sail, WHOI engineer Rich Ahern launched a sleek, autonomous vehicle in the Gulf called Spray glider, a joint operation with the California-based Scripps Institution of Oceanography. Shaped like a shark, it has a wing on each side and a vertical tail fin.
Six other gliders are at work in the Gulf.
Breck Owens, at WHOI, programmed Spray to stay in the water for four months and search for underwater plumes of oil. It can dive to 500 metres, and uses acoustic equipment to sense particles suspended in the water.
The glider also has an antennae embedded in a wing tip and sends data to Owens and Scripps in real time, via email. Owens can send new instructions to the glider on a satellite phone.
"We should take advantage of this opportunity to evolve a proper observing system in the Gulf," Owens said at a WHOI conference.
The glider's data made clear in June that the Loop Current, the movement of warm ocean water into and out of the Gulf, had formed an eddy, and that the oil in the Gulf would likely not travel up the eastern coast of the United States.
The WHOI scientists are analysing their data now and expect to release their results within a few weeks.
This information can be used to determine how successful the cleanup has been, and what should still be done during this spill and others in the future, Reddy said.
But not all scientists need to use high tech to get the answers they are after. Alexander Kolker, a wetlands expert with the Louisiana Universities Marine Consortium, is studying the impact of the spill on a 3,000-square-km area along the southern Louisiana coast called Barataria Bay.
He gathers water samples and sediment cores from the marsh using his small motorboat and hauls them back to his lab for analysis.
"It's an incredibly productive ecosystem," he told Tierramérica, noting that it serves as habitat for hundreds of species. Oil from the BP spill covers part of the marsh, but the damage it has caused is not as great as the constant die- off of grass there as a result of salt water intrusion, he said.
The U.S. government agencies overseeing the Gulf cleanup released a report recently that offered a rosy picture of the fate of the oil following the spill.
"It's important to point out that at least 50 percent of the oil that was released is now completely gone from the system. And most of the remainder is degrading rapidly or is being removed from the beaches," Jane Lubchenco, head of the National Oceanic and Atmospheric Administration, said of the report.
But Reddy, like many independent scientists, believes it is too early to draw conclusions about the fate of oil in the Gulf. "Why rush? Let's wait and get all the good data that's out there," he said.
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