Oil May Linger in Gulf Region for 100 Years

Image by B.G. Johnson via Flickr

"I've been told by the ocean experts this stuff could hang out there on the bottom of the Gulf for more than 100 years. And as long as it's out there, it can come ashore."

www.nola.com
Louisiana coast's battle against drifting oil expected to last months, if not years
Bob Marshall, The Times-Picayune
For those saddened by the scenes of thick oil washing into Louisiana's coastal wetlands a month after the BP oil disaster began, experts on oil spills and the coastal ecosystem have some advice: Get used to it.

The crews mopping up oil on beaches and marsh shorelines this week are fighting just the first of what will probably be a series of rolling skirmishes that will last for months, if not years -- even after the runaway well is finally capped. In fact, the untold millions of gallons of oil already fouling the Gulf off the Louisiana coast could stay in the area for at least a decade, and on the sea floor for more than 100 years.

"I'm afraid we're just seeing the beginning of what is going to be a long, ugly summer," said Ed Overton, an LSU professor who has consulted on oil spills for three decades.

View full size
Michael DeMocker/The Times-PicayuneOil on the beach in Grand Isle was photographed Friday.

"I hope and pray I'm wrong, but I think what we're in for is seeing a little bit come in each day at different places for a long, long time -- months and months.

"That's not what I said in the beginning of this. But events have made me amend my thoughts."

When it began April 20, Louisiana and the world feared a quick and dramatic result, a black tsunami washing over one of the world's most productive and valuable coastal ecosystems. Expecting a disaster with iconic images to rival the environmental mugging of Prince William Sound by the Exxon Valdez, the planet's media rushed to the scene. Within days fishing towns like Venice and Hopedale became datelines in newspapers from Paris to Hong Kong, which painted pictures of a culture bracing for ecosystem Armageddon.

But for weeks, little happened on shore. Even as the amount of crude spewing from the 19-inch hole in the Gulf climbed, the wetlands and its critters remained healthy.

That began to change this week. Thick oil invaded the wetlands of the Mississippi River delta, then began spreading westward, rolling up on coastal beaches and barrier islands from Grand Isle to Marsh Island in Vermillion Bay.

But even this hasn't been an inundation. The oil has been in long, narrow lines. And there seems to be no discernible weather pattern associated with the arrivals. They have cropped up on calm days and rough, and days with little tide range.

That random pattern, experts now say, is probably the best guess of what the state should expect for many months ahead. And they stress the "guess" part, because the location of the runaway well and the environment into which it is flowing make it unprecedented in the history of oil disasters.

"We learn from experience, and the last experience we had with a big spill was the Exxon Valdez, so naturally people expected similar results," said LSU oceanography professor Robert Carney, who has done extensive research on the Gulf of Mexico.

"But everything about this is so radically different."

The Exxon Valdez accident released 11 million gallons of crude from a tanker onto the surface of an enclosed body of water close to a rocky, static shoreline, Carney said. The BP disaster is pouring tens of millions of gallons from the floor of the Gulf 5,000 feet below in an open sea, and 50 miles from the nearest land, which is a composed of broken marshes, river deltas, open bays and barrier islands.

"Because no one has experience with a situation like this, all we can really do is take educated guesses," Carney said. "There are so many things to consider when trying to track the oil plume."

The biggest unknown is the oil's journey to the surface -- and that is what has made predicting where and how it will come ashore such a challenge, scientists said. That difficulty was clear in initial estimates of how long the oil would take to get to the surface. "Originally it was three hours to 30 days," Overton said. "That shows you just how many variables are involved."

In a static and shallow environment, oil, which is much lighter than sea water, would zip to the surface like an ice cube from the bottom of a glass of water. But nothing is static in this environment.

Researchers say there are numerous currents in that part of the Gulf between 5,000 feet and the surface, each of which can grab some of the plume and shuttle it in different directions. There also are different temperatures layers that also can redirect portions of the plume. At a depth of about 1,500 feet, a cold layer meets a much warmer layer of water, and the change in density creates a virtual wall that can trap particles.

"Anything that stays below 1,500 feet can stay in deep circulation in the Gulf for an extended period of time," Carney said. "I would say deep oil might be detectable in that environment for 10 years."

Misconceptions about the nature of the flow also abound, Overton said. The oil spewing from that open pipe is not the pure viscous liquid that pours from an oil can. Instead, it's natural gas mixed with oil droplets that probably vary in size from an egg to ink dots, blasting out of the Gulf floor with the force of a powerful fire hose at full throttle, he said.

Video from the scene shows billowing clouds of the mixture spilling from the break. What it doesn't show, Overton said, is what type of plume that mixture is forming.

"We really need to know that, but we can only guess," he said. "And my guess is that it's been spreading out across a large area, sort of like the way smoke from a forest fire spreads across the landscape on a calm day."

It's obviously not all rushing to the surface like that ice cube in the glass of water, Overton said. That complicates the job of collecting it and predicting when, where and in which quantities it will come ashore.

A further complication has been the undersea use of dispersants, Overton said. Breaking the oil into small "micro" droplets at that depth may be reducing its buoyancy, causing it either to sink to the bottom or stay suspended somewhere under the surface.

"They will float below the surface, where they can't be reached by the weathering agents like sun and wind and air," Overton said. "Eventually they will stick together and form larger droplets and begin moving toward the surface.

"But that could take month or years. We could be seeing these things rise and wash up on the coast for years to come."

Overton said this week's oiled beaches strengthened that hunch.

"The pictures I saw included a lot of black oil," he said, "and that tells me it could be oil that just came to the surface. If that's the case, then a lot of this oil is still suspended, moving to the coast without being weathered on the surface, probably because of the subsea dispersants.

"So the reason we haven't seen big coatings, may be because much of it is still below the surface."

In fact, the consensus building among scientists and oil spill experts this week was that BP's mistake likely will never result in a black wave soaking miles of coast in thick layers of black oil. Instead, Louisiana is probably in for a years-long war of mostly small skirmishes against random, low-volume oilings of coastal marshes and beaches.

"I think we're looking at many months of intense activity, but then years of follow-up work," said Robert Barham, secretary of the Louisiana Department of Wildlife and Fisheries.

"I've been told by the ocean experts this stuff could hang out there on the bottom of the Gulf for more than 100 years. And as long as it's out there, it can come ashore.

"We might not see big black waves, but we may be seeing a smaller, but serious problem, for years and years to come."