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5. Tracking the Currents

Concern about the impacts of the spill centered on the northern Gulf of Mexico, but some feared that oil might also reach the U.S. East Coast, via the “Loop Current.” If that happened, damage from the spill would be more widespread and cleanup efforts would have to encompass a much larger area.

The Loop Current typically flows north from the Caribbean, loops up close to Louisiana, then turns south, zips around Florida, and merges with the Gulf Stream. However, a few times a year, the part of the Loop Current that reaches far north into the Gulf pinches off, like the oxbow of a river. When that happens, the closed loop forms an eddy that spins its way slowly westward across the Gulf, while the main stream of the current swoops past the tip of Florida without taking water from the northern Gulf with it.

If an eddy formed, it might prevent oil from reaching the East Coast. The trouble was, eddies are unpredictable. No one knew if or when one would form.

WHOI oceanographer Breck Owens and his colleagues at Scripps Institution of Oceanography had already done some work on the Loop Current using Spray gliders, torpedo-shaped vehicles that are the highly evolved descendants of floats conceived decades ago by pioneering WHOI oceanographer Henry Stommel to study ocean circulation. In their earliest forms, floats were made to move passively wherever currents took them. It was the “message-in-a-bottle” approach: Put a float in the water and see where it goes.

Owens, working with Russ Davis and Jeff Sherman at Scripps, developed the Spray about ten years ago. Like its ancestors, the Spray can’t propel itself—but it can steer left or right by means of fins, and up or down by changing its density. Outfitted with instruments that measure salinity, temperature, and other ocean properties, the Spray can detect distinct masses of water such as the warm Loop Current. When the designers added GPS and a satellite phone link allowing it to be guided by oceanographers thousands of miles away, the Spray became a versatile, responsive device for detecting and monitoring currents for weeks or months at a time.

It was ideally suited to find out whether the Loop Current was beginning to form an eddy in the weeks after the oil spill.

WHOI personnel in this video:

Breck Owens

Breck Owens

Physical oceanographer
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