“Forbidden Zone” Likely to Keep Oil Away From our Coast
With all the oil spewing into the Gulf of Mexico and the pictures all over the television and the Internet of Louisiana beaches and marshes covered in icky red goo, many islanders and visitors alike are understandably terrified that one day our beach could resemble those already hit. However, I discovered this week that the liklihood of that happening is very low. In fact, mainly due to our geographic location, many scientists are saying that the most we’ll ever see are a couple of tarballs here and there – and maybe not even that.
“There is a ‘forbidden zone’ off the southwest Florida coast where the shape of the coast, bottom configuration, and prevailing winds all act to create upwelling and surface currents that tend to take water away from the coast,” says Dr. Jeff Jeff Masters, lead meteorologist and founder of Weather Underground.
A study conducted by the Minerals Management Service (MMS) in the late-90’s seems to prove that notion. During the course of the yearlong study, the MMS released 194 floating probes, which were allowed to drift around in the Gulf, including the Loop Current. Almost none reached the west coast of Florida from Tampa Bay southwards to the Everglades.
Other researchers have reached similar conclusions.
Two weeks ago, the National Center for Atmospheric Research (NCAR) issued a press release showing 4-month model runs of where the Deepwater Horizon oil spill might go. The model runs show that given typical ocean currents in the Gulf of Mexico, they can expect the oil to eventually affect most of the Florida Panhandle, Keys, and Florida East Coast, as well as coastal areas of South Carolina and North Carolina. Very little oil makes it to the West Florida “Forbidden Zone”, where offshore-moving surface currents dominate.
According to the NCAR’s website, “Scientists injected a virtual dye into the simulation at a constant rate to mimic a continuous flow. The dye shows how the currents transport and dilute fluid, but do not take into account the viscosity of oil or its natural breakdown. The dilution rate, however, can be used to estimate how much oil will arrive in certain locations.”
“The scientists used a powerful computer model to simulate how a liquid released at the spill site would disperse and circulate, producing results that are not dependent on the total amount released. The scientists tracked the rate of dispersal in the top 65 feet of the water and at four additional depths, with the lowest being just above the seabed.”
“Scientists ran six different simulations of the constantly fluctuating loop current to see a range of possibilities for where the oil could travel. Most of them produced similar results.”
Below Surface Oil
What about oil below the surface?
“If the oil is deep enough, it could encounter a sort of speed bump along the Loop Current,” said University of Miami oceanograher Peter Ortner. “As the current emerges from the Gulf and makes a turn into the Florida Straits, it moves over a sill that is shallower than the Gulf. Oil deeper than the sill might have a hard time getting over the hump.”
To further investigate the presence of oil below the surface, this week NOAA released underwater unmanned gliders that will capture data that to assist in locating and tracking oil at various levels in the water column as well as on the Gulf surface.
Ten unmanned underwater robots will measure matter in the water, which can help indicate the presence of oil. These gliders are also capable of collecting temperature, salinity, currents, density and additional variables that describe conditions below the surface of the sea. The gliders travel at various depths - some gliders dive no deeper than 100 feet, while others are capable of collecting data nearly a mile underwater.
Readers may recall that the Sand Paper reported last week that robots released by the Mote Marine Laboratory to survey the Gulf waters from Sarasota to Key West in about water about 100 feet deep have found no traces of either pure oil, weathered oil or oil with dispersants.
No Direct Route South
And then there is the issue of the eddies. Scientists point to the fact that eddies frequently break off from the Loop Current. This ‘beheading’ would carry the oil towards the west.
“Beheading is common to the current, which becomes more unstable as it pushes deeper into the Gulf of Mexico. Typically, a forceful counterclockwise cyclone near southwest Florida “punches through the Loop Current,” severing the flow from its connection to the Atlantic,” said Nan Walker, the director of the Earth Scan Lab at Louisiana State University’s School of the Coast and Environment.
Dr. Masters agrees.
“The present ocean current configuration in the Gulf features a newly formed Loop Current Eddy (dubbed “Franklin”), which will tend to capture the majority of oil that flows southwards from the Deepwater Horizon spill site,” he said in a blog posted on June 30th.
“A plot of drifting buoys (drifters) launched into the Gulf May 19th – 24th reveals how this clockwise-rotating eddy has been capturing southward-moving surface water. Eddy Franklin will move slowly west-southwest at 2 - 3 mph in the coming weeks. By August or September, the eddy will have moved far enough west that the Loop Current will be able to push northwards towards the spill location again, increasing the chances of oil getting into the Loop Current and being advected through the Florida Straits and up the U.S. Southeast Coast. Between now and mid-August, I doubt that a significant amount of oil will get into the Loop Current, unless a hurricane or tropical storm goes through the Gulf of Mexico.”
Masters predicts that the Loop Current Eddy will move slowly westwards toward Texas at about 4 miles per day after it fully cuts off.
“When it reaches the shallow waters near the Texas coast in early 2011, the eddy will turn northwards and gradually dissipate,” he said. “By then, I expect that the vast majority of the oil in the eddy will have dispersed, sunk, or evaporated.”
Jennifer Johnson of the Florida Peninsula Command Center in Miami told us that all of her support staff point to the fact that the Deepwater Horizon oil head is 400 miles from the Dry Tortugas.
“The stuff folks are seeing on TV is right near the well,” she said. “South Florida is about 600 miles from the Deepwater Horizon wellhead so any oil coming anywhere near here will have gone through serious currents and weatherizing and not resemble one bit what they are seeing in Louisiana.”
G. Gerald Campbell, Chief of Planning for the Lee County Division of Public Safety and Emergency Management, said that the oil isn’t even in the Loop Current now, something we confirmed by going to NOAA’s response on the website www.dep.state.fl.us/deepwaterhorizon/.
“Observations by NOAA continue to indicate no significant amounts of oil moving toward the Loop Current,” a June 30th statement reads. “The Loop Current Ring, a circular current which was formerly part of the Loop Current provides no clear path for oil to enter the Florida Straits.”
In fact, NOAA has discontinued its offshore forecasts for the oil spill due “to small amounts of oil offshore, the absence of recent observations confirming significant amounts of oil in offshore areas and the large separation between the loop current complex and the oil slick”.
Continued Monitoring
On Wednesday, a NOAA research ship and a university-owned vessel left Miami to begin two studies gathering data on the Loop Current and area ecosystems.
According to a news release issued yesterday, “NOAA Ship Nancy Foster begins today a two-week survey in the eastern Gulf of Mexico and the Florida Straits. Nancy Foster is one of six NOAA-owned ships supporting the oil spill response effort. Scientists from NOAA’s Atlantic Oceanographic and Meteorological Laboratory in Miami and the NOAA Southeast Fisheries Science Center will lead the expedition to track where the oil has been and to determine where it may go. So far, oil from the Deepwater Horizon/BP oil spill has not entered the Loop Current.”
“In addition, the Nancy Foster scientific team plans to monitor connectivity between the Loop Current and the Loop Current “Eddy Franklin” during the first week, and to study surface and subsurface waters in the east and north parts of the eddy during the second week.”
Another boat, the Savannah, operated by the Skidway Institute of Oceanography in Savannah, Georgia, is sailing through the Keys and the western Florida shelf to monitor that area.
Whatever they find, if anything, is not likely to resemble the aerial shots of reddish goo stretching to the horizon. According to the latest information on NOAA’s website, “It is unlikely that large, cohesive oil slicks will reach Florida waters. Instead, on the water surface, expect to see floating tar balls and/or scattered patches of weathered oil, perhaps mixed with Sargassum (algae) or other floating material.”
Keri Hendry
