As a tendril of oil from BP's Deepwater Horizon disaster creeps south in the Gulf of Mexico—potentially already caught up in the swirl of a massive conveyor of ocean water known as the Loop Current—the larger question is, where will the at least 5 million gallons of oil already spilled end up?
"The proximity of the southeast tendril to the Loop Current means it is increasingly likely to become entrained," said marine biologist Jane Lubchenco, administrator of the U.S. National Oceanic and Atmospheric Administration (NOAA) at a press briefing on May 18. If that happens, the oil will "reach Florida straits in eight to 10 days." Though tar balls found in Key West have not been linked to the ongoing spill, "the tar balls washing ashore in the Florida Keys are an example of what might happen should the oil become entrained in the Loop Current," Lubchenco said.
The Loop Current is just one part of a massive system of oceanic conveyor belts—and one that feeds into the more broadly known Gulf Stream that flows past the entire U.S. East Coast. At the same time, an eddy—a swirling maelstrom of seawater—is flowing in a circle directly above the Loop Current in the Gulf. So the oil is like a baseball in a pitching machine, caught between two swirling currents and just as likely to head north to the Gulf Coast as south to Florida and the Atlantic.
"If this stuff comes onshore, a lot of birds are going to die," said ecologist Roger Helm, chief of the division of environmental quality at the U.S. Fish and Wildlife Service (FWS). As a result, the Department of the Interior has teamed with a number of Gulf states to submit a proposal to the Army Corps of Engineers to build a giant sandbar offshore of barrier islands—a relatively permanent way to keep the oil off the coast. "The project is still being developed," said FWS acting director Rowan Gould, a marine biologist, at the May 18 press briefing. "There is no timeline about when any decisions are going to be made."
As for oil beneath the surface, which may have been detected in massive plumes by the research vessel Pelican, that is more likely to remain in place. "Below 50 meters, the velocity of this current drops off dramatically," said NOAA chief science advisor Steve Murawski, a fisheries biologist, giving those oil particles more time to clump and sink to the bottom or wash ashore. But what happens when the oil hits those communities that live on the seafloor, such as Lophelia coral, remains unknown. "This ecosystem is not totally devoid of at least some hydrocarbons in the water," Murawski added. "Those issues are going to play out over time as we document where the oil has been and at what concentrations.... We've never had this substantial an oil leak a mile down."
Added NOAA director of marine mammal health and stranding response Teri Rowles, a veterinarian, impacts on "those species living in deep water, like sperm whales, may not be detected," because dead whales simply disappear beneath the waves. Plus, the use of dispersants beneath the surface to break up the oil into droplets may make it more damaging to deep-sea wildlife. "Instead of having big chunks of oil that are very buoyant and move very quickly to the surface, you have microdroplets with an enormous surface-to-volume ratio, which then are captured by the viscosity of the seawater. They're stuck down there," says environmental chemist Jeffrey Short of environmental group Oceana, who has studied the aftereffects of the Exxon Valdez spill. "Ancient deep-water corals, which are suspension feeders, are extraordinarily efficient at accumulating microdroplets of oil. It's a major unseen impact."
Much of the oil will also end up trapped in big eddies—like the infamous Pacific Garbage Patch or the Sargasso Sea—which is where sea turtles and other ocean life like to congregate. "Most of those mortalities will never make their way to shore to be counted," said NOAA national sea turtle coordinator Barbara Schroeder.
As a result of all this, NOAA has extended its fishery closures to shut down more than 45,000 square miles of Gulf waters—roughly 19 percent of all federal waters in the Gulf of Mexico. "This spill is significant and in all likelihood will affect fish and wildlife across the Gulf, if not all of North America, for years if not decades," said FWS's Gould. "We may never know the spill's impacts on many species of birds and marine life, given how far offshore they are found."
And ultimately, if the oil gets pulled by the Loop Current into the Gulf Stream, it will end up far to the north: the Arctic. "A lot depends on what the ocean currents do and what the winds do in terms of actual transportation," Lubchenco said, although it is clear that high-speed travel will expose the oil to more weathering and more dilution, which reduces its impact on ocean ecosystems. Once in the far north, the remnants of the oil would sink to the bottom, entering the cold, dark deep for a millennia-long journey along the seafloor. "This oil spill is unprecedented and dynamic," Lubchenco said, and it is likely to be part of the ocean for a long time.