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Robert H. Weisberg

Nature puts Florida
back in the loop

The Gulf of Mexico Loop Current became a household term last year when people feared that oil gushing from the Deepwater Horizon wellhead would be carried by the Loop Current to the Florida Keys and up the East Coast. Instead, an eddy broke off from the Loop Current, breaking the connection with the Florida Keys and keeping the spill contained to the northern gulf.

In short, much of Florida got lucky. But this luck wouldn't have held out this year. In fact, if the oil was spilling right now, the Loop Current would be doing just what experts feared last year — polluting a long stretch of Florida and the East Coast.

The Gulf of Mexico Loop Current is part of the North Atlantic Ocean's western boundary current system, which connects the Caribbean Sea, the Gulf of Mexico, the Southeastern United States and points farther north. Entering the gulf through the Yucatan Strait, the current loops clockwise, hence its name, before exiting through the Florida Straits, where it is called the Florida Current, and then continuing north as the Gulf Stream.

This massive, ever-present ocean current owes its existence to heating by the sun, plus the rotation and spherical shape of the Earth. These factors result in winds and ocean currents that are nature's way of transporting heat from the tropics to the poles. In combination, this coupled ocean-atmosphere circulation is what determines Earth's climate.

Because the Loop Current contributes to the ocean temperature around Florida, it directly influences Florida's climate. By virtue of the Loop Current's connectivity, it also influences where materials spilled into the ocean may end up, hence the concern last year during the Deepwater Horizon oil spill.

The position of the Loop Current within the Gulf of Mexico is highly variable. At times the Loop Current flows directly from the Yucatan Strait to the Florida Straits without penetrating northward. More generally, though, it cycles back and forth from south to north, reaching almost to the Mississippi River Delta, or even as far west as the longitude of Texas, before breaking off a piece — an eddy — and then retreating to the south to start its northern migration and eddy shedding cycle anew. Each cycle generally lasts 8 to 16 months.

Many of the present Gulf of Mexico oil production platforms are located just to the north of the Loop Current's historical pathway axis. New, deeper ocean production platforms will likely be within the historical pathway, and the proposed drill sites north of Cuba are almost always within the Loop Current's path.

Early into the Deepwater Horizon oil spill last year, it was the pinching off of an eddy that broke the connection between the well site and the Florida Keys, thereby sparing South Florida and the East Coast from any significant oil encounters. Each year is subtly different, however. A Loop Current eddy just recently formed and broke off in an almost identical manner as occurred last year; but, instead of remaining separated, the eddy rapidly reconnected with the parent Loop Current. So we may speculate that had the Deepwater Horizon blowout occurred this year, there would now be oil flowing through the Florida Straits and up the East Coast.

Indeed, given the Loop Current speeds, analyses of historical data show that the travel times are quick. From the Yucatan Strait to the Florida Straits the average travel time is 20 days, plus or minus nine days, and from the Florida Straits to Cape Hatteras, 15, plus or minus two days.

Similarly, if the Loop Current were to extend to the vicinity of the Deepwater Horizon wellhead, as it nearly does now, the travel time to the Florida Straits is only about one week. We may conclude that as bad as the oil spill was for northwest Florida last year, much of Florida actually lucked out. That may not have been the case if the Deepwater Horizon blowout occurred at the same time this year.

Such oceanographic discussions for Florida extend far beyond oil spills, hypothetical, or real. As a peninsula nearly surrounded by water, Florida's economy is in every way touched by the ocean. It is vital that we continually advance our understandings on the complex workings of our estuarine, coastal and adjacent deep-ocean regions to better serve the citizens of Florida and the nation.

Much remains to be learned, and strong academic oceanographic research programs in partnerships with our management agencies are essential for doing this. We cannot effectively manage complex systems that we do not adequately understand.

Robert H. Weisberg, distinguished university professor, is a professor of physical oceanography in the College of Marine Science at the University of South Florida St. Petersburg.

Nature puts Florida
back in the loop
06/03/11 [Last modified: Friday, June 3, 2011 7:59pm]

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