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Whirlpools born off the coast of Pernambuco

Vilela-Silva, F. et al. Jgr: Oceans. dec. 22, 2022 Map showing the movement of eddies (blue circles) along the Brazilian coastline on January 20, 2002. In the lane, blue patches indicate counterclockwise rotation, green ones show clockwise movementVilela-Silva, F. et al. Jgr: Oceans. dec. 22, 2022

At depths of between 1,000 and 4,000 meters (m), a marine current transports nutrients and salty, oxygen-rich, cold water from the Labrador Sea in Greenland to Antarctica. Off the coast of Recife, on the Pernambuco Plateau, the current breaks into whirlpools known as eddies that rotate counterclockwise as they travel thousands of kilometers southwestward, all the way to the coast of Espírito Santo, stirring up water and nutrients. The width (approximately 250 kilometers) and the speed (0.04 m per second) of these eddies had already been measured, but how they are formed remained unknown. Now, scientists from the University of São Paulo (USP), in collaboration with colleagues from Australia, France, and the USA, have shown that the eddies are created by the interaction between the marine current and the Pernambuco Plateau (JGR: Oceans, December 22). The conclusion was based on the analysis of data collected in 2002 by the Brazilian Navy’s oceanographic vessel Antares in conjunction with computer modeling. “Identifying the mechanism through which the current breaks on the Pernambuco Plateau allows us to better understand heat flows and oxygenation at the bottom of the tropical Atlantic,” says USP oceanographer Felipe Vilela-Silva, the lead author of the paper.