Tuesday, June 15, 2010

'Oil spill residuals' on Outer Banks in September-April time frame?

Michael Voiland, head of the N.C. Sea Grant program at N.C. State University, met with his counterparts in other Southern states last week to discuss the oil spill in the Gulf and what might happen if things go wrong and the oil comes up the East Coast. Oil residuals in some form might show up at Cape Hatteras and other Outer Banks beaches in the September-April time frame, the group things.  Here are a few of the group's conclusions:

* Despite estimates by BP and federal agencies, the amount of oil that has spilled into the Gulf is essentially unknown. The actual volume of oil spilled there will affect the chances of it reaching South Atlantic waters.

* It is still highly speculative to pinpoint the location, depth, and amounts of GoM oil that might eventually be captured and transported by the Loop Current over specific periods of time.

* The first major step in any movement of Gulf oil to the South Atlantic would be its entrainment in the GoM's Loop Current. In recent weeks and at present (June 11, 2010), the Loop Current has been “pinched” at its ox-bowed (loop) narrowing, creating an eddy or gyre separated from the Loop Current itself. This fluctuation, manifested as a separated eddy, has acted as a barrier to major movement of oil into the Loop Current.

* Once oil borne by the Loop Current reaches the southeast end of the Florida peninsula, it then could become captured by the Gulf Steam and move to the north, offshore of the east coasts of FL, GA, SC and NC.

(See: http://www.skio.usg.edu/?p=news/showarticle&n=128 )

* The risk of having oil spill residuals come ashore would be greatest along the southern portion of Florida’s east coast, due to closer proximity of the Gulf Stream to that shore. Factors affecting the prospects and amounts of oil reaching the shoreline include shearing and eddy effects along the Gulf Stream’s west (inshore) edge, prevailing winds and their speeds, and acute weather events.

* A second area in the South Atlantic that would be at higher risk for oil spill residuals coming ashore is at North Carolina’s Cape Hatteras and neighboring Outer Banks beaches, and especially in the September to April time frame. Again, this would be mainly driven by proximity of the Gulf Stream to the shore and weather events, but also by onshore eddies and jetting actions caused by interactions of the Gulf Stream near Hatteras with southerly flowing currents of cooler water from the north.

* Shorelines and waters between south Florida and Cape Hatteras also could experience visible oil deposits, diluted concentrations of oil, and other effects. Manifestations of oil will likely be more highly dependent on acute weather events (significant coastal storms), prevailing wind direction and speeds over set periods of time, and seasonally-related perturbations (e.g., eddies, meanders, “spin-offs”) along the inshore (western) edge of the Gulf Stream.

* The expert panel noted that the longer Gulf oil remains at sea, the more likely natural degradation of the oil could take place. As such, it is possible that oil reaching south Florida waters may be in more visible forms such as sheens, slugs, and tarballs; while oil that makes it to Hatteras waters may be more diluted and dissolved — and, if conspicuous at all, perhaps only seen in forms such as water color/turbidity differences, thin oily residues on contact objects, and smaller tarballs.

Katie Mosher, spokesperson for the program, cautions that Voiland's comments about residual oil coming ashore at Hatteras were not meant to be ominous or dire

"The reference to oil spill residuals is vague because we do not know what exact form degraded oil from the Deepwater Horizon would have after weeks of weathering as it may move. The experts do not want to speculate so far out. But the panel did want to note that Cape Hatteras is closer to the Gulf Stream than other parts of the NC coast, or the coastlines for SC, GA and northern FL. Of course, the southern FL area is closest to the Gulf Stream."

Coincidentally, Gov. Bev Perdue is briefing legislators and local government officials this morning on the state's Emergency Preparedness office's plans for dealing with the oil spill should the need arise.

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