(Their trackers have likely reached the end of their five-year lifespan, but both sharks still maintain active twitter accounts: and gained some notoriety as the first white shark to be tracked crossing the Atlantic, while Mary Lee tended to stay a little closer to the coast. Lydia, slightly smaller at 14.5 feet and just under one ton, was tagged off Jacksonville, Florida, in March 2013. Mary Lee, 16 feet long and 3,460 pounds, was tagged off the coast of Cape Cod in September 2012. The research team followed two mature white sharks. To the scientists’ surprise, the sharks spent most of their time in the warmer eddies.
So it might seem logical that when adult white sharks leave the seal-filled waters of coastal New England and head for the open ocean, they might seek out these whirling blobs of cold water, where phytoplankton at the base of the food chain are blooming. “They’re anomalously cold and anomalously productive.” The extra nutrients can fuel enough phytoplankton growth to make these eddies visible from space. “They trap cold, nutrient-rich water from north of the Gulf Stream,” Braun said. “The paradigm is that they’re like these ocean deserts,” said Camrin Braun, a graduate student in the MIT-WHOI Joint Program in Oceanography and co-author of the new study published in May 2018 in Scientific Reports.Ĭold-water eddies are just the opposite. But because that water is typically low in nutrients, these eddies aren’t thought to contain much life. When the eddy spins away from the current, it traps that warm water in its center. The warmer eddies are spawned when the Gulf Stream snakes farther northward, drawing warm water up from the Sargasso Sea. The Gulf Stream can spin off both warm- and cold-water eddies, and surprisingly, the sharks seem to have a preference.
They found that white sharks in the open ocean seem to seek out eddies for a surprising reason: The eddies offer a beeline to a banquet of food. It’s a discovery by researchers from the Woods Hole Oceanographic Institution and the University of Washington, who tracked the movements of several tagged great white sharks. No, this isn’t the plot of the next Sharknado movie. These swirling pockets, called eddies, may also be full of sharks.
If one of these swirls is large enough, it will pinch off, sending a whirling pocket of water-more than 60 miles in diameter-spinning through the ocean like an underwater hurricane. As the Gulf Stream current curves away from North America and heads east across the Atlantic, it swirls at its edges.
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