A thin stem of oil stretching east from BP PLC's spill is increasingly likely to enter the Loop Current, a powerful Gulf of Mexico flow that runs past the Florida Keys and up the Atlantic Seaboard, the National Oceanic and Atmospheric Administration chief said today.
Stark satellite imagery released yesterday revealed that, while the large majority of oil remains bobbing off the Louisiana coast, "a tendril of light oil has been transported down toward the Loop Current," NOAA Administrator Jane Lubchenco said.
In fact, oil may already be entrained in the current, Lubchenco said, and NOAA is sending imagery aircraft out today to determine the extent of the oil's drift.
Once oil is in the current, it would likely reach the Florida Keys within 10 days. By month's end, the oil could reach Miami, oceanographers have also warned.
"The oil, if it gets into the Loop Current, will become very, very dilute and will be highly weathered," she said, arriving at the Keys most likely in the form of tar balls and emulsified streamers.
Any oil or dispersants pulled south to the Florida Straits could pose an environmental hazard, especially for coral reefs, said Nan Walker, the director of the Earth Scan Laboratory at Louisiana State University.
"The dispersants could kill corals," Walker said earlier this month. "Obviously, oil is not going to be good for corals. That is probably one of the biggest concerns if [the oil] was entrained."
Reflecting this spread, NOAA has expanded its fishing restrictions over a larger portion of the Gulf. The closed area is 24,241 square miles, covering some 10 percent of the Gulf's exclusive economic zone. The restrictions apply to commercial and recreational fishing, the agency said, but not transit.
It is impossible to predict how much oil will travel southward. Currently, the tendril sits in a sinuous line between the northern boundaries of the Loop Current and the southern limits of a small, counterclockwise current, known as an eddy, that could draw the oil back north.
The oil can be thought of as a stream of cars traveling on an eastward-running highway that is about to turn north, with an exit peeling off south toward the Loop Current. Scientists have little certainty about the size of the exit or how much oil will take that turn. All that is certain is that exit leads, eventually, to Florida.
Federal agencies have been monitoring the current from the spill's outset and are now preparing for potential impacts around the southern Florida coast, Coast Guard Rear Adm. Peter Neffenger said yesterday during congressional testimony. Tar balls, he said, would be a "more manageable piece" to clean up in Florida than the vast oil deposits now spreading in the Gulf.
Homeland Security Secretary Janet Napolitano added that the government is treating the Loop Current "as if it's its own coastline," meaning the government will undertake prevention and response efforts as if the Loop Current were a piece of shoreline, she said.
Florida Keys in bull's-eye
The Keys would likely be the first coastline to feel the oil's effects in Florida. The current sits far off Florida's western coastline and will likely spare areas like Tampa, according to Steve Murawski, NOAA's chief science adviser for fisheries.
The Coast Guard said yesterday that 20 tar balls have already washed ashore at Fort Zachary Taylor State Park in Key West. The tar balls, which were found by park rangers, range from 3 to 8 inches in diameter. They will be sent to a laboratory for analysis to determine whether they are associated with the Deepwater Horizon spill.
The Coast Guard and NOAA will conduct shoreline surveys beginning today in the Florida Keys National Marine Sanctuary.
Whether or not the tar is connected to the BP spill, Lubchenco said, it is "safe to say that the tar balls washing ashore in the Florida Keys are an example of what might happen should oil become entrained in the Loop Current."
Independent oceanographers are now practically certain some of the oil will enter the current and have long warned that the unpredictable flow posed a threat (Greenwire, May 5). All four forecast models at the University of South Florida now predict that at least a portion of the oil slick's branch will migrate from the eddy into the current.
How much oil takes that path will depend on how the eddy, which has been growing stronger over recent days, evolves, said Villy Kourafalou, a Gulf of Mexico modeler at the University of Miami's Rosenstiel School of Marine and Atmospheric Science.
"Any pathways along the Loop Current strongly depend on the evolution of the eddy field," Kourafalou said. "It is clear that the north cyclone has started to entrain oil. It is not in the Loop Current main front yet. It is a high possibility that it will."
There is a possible positive sign, in that imagery yesterday from NASA seemed to indicate that a portion of the slick's eastward-facing "tail" seems to be turning northward, said Tony Sturges, an oceanographer at Florida State University.
"The only good part is that right at the end, the 'tail' appears to curve out and back away from the main flow," he said. Still, he added, the current imagery is "not a good sign."
It is less clear how oil deeper underwater and closer to the spill's main body will behave, NOAA's Murawski said. Past 1,500 meters underwater, he said, the currents drop dramatically and do not pull toward the Loop Current, at least currently.
Reporters Noelle Straub and Katie Howell contributed.