Eddies as Deep, Powerful Modes of Ocean Transport

Hydro International -

Researchers from Woods Hole Oceanographic Institution (WHOI) and their colleagues have discovered that massive, swirling ocean eddies, known to be up to 500 kilometers across at the surface, can reach all the way to the ocean bottom at mid-ocean ridges, some 2,500 meters deep, transporting tiny sea creatures, chemicals, and heat from hydrothermal vents over large distances.

The previously unknown deep-sea phenomenon, reported in the 28 April issue of the journal Science, helps explain how some larvae travel huge distances from one vent area to another, said Diane K. Adams, lead author at WHOI and now at the National Institutes of Health.

Using deep-sea moorings, current meters and sediment traps over a six-month period, along with computer models, Adams and her colleagues studied the eddies at the underwater mountain range known as the East Pacific Rise. That site experienced a well-documented eruption in 2006 that led to a discovery reported last year that larvae from as far away as 350km somehow traveled that distance to settle in the aftermath of the eruption.

The newly discovered depth of the powerful eddies helps explain that phenomenon but also opens up a host of other scientific possibilities in oceans around the world. The eddies are generated at the surface by atmospheric events, such as wind jets, which can be strengthened during an El Niño, and “are known to have a strong influence on surface ocean dynamics and production,” say Adams and Dennis J. McGillicuddy from WHOI, along with colleagues from Florida State University, Lamont Doherty Earth Observatory, and the University of Brest in France. But this “atmospheric forcing…is typically not considered in studies of the deep sea,” they report.

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