Textbooks depict the Gulf Stream, the Kuroshio, and other great ocean currents as smooth, riverlike streams. Reality is messier. Gravitationally bound to the spinning globe, the oceans constitute a complex, turbulent system.

Indeed, the Gulf Stream is so variable that the organizers of the biannual Newport-to-Bermuda yacht race feel it prudent to provide competitors with three pre-race reports of the current’s strength, direction, and whereabouts.

Now, a computational and field study has found that turbulence influences not only the variability of ocean currents but also whether water flows in an identifiable current at all. 1 The study was led by Amy Bower of Woods Hole Oceanographic Institution in Massachusetts.

Bower’s subject is the southward flow of cold, deep water from the Labrador Sea to lower latitudes in the Atlantic. In winter, winds blow eastward over Canada’s tundra. When those winds reach the Labrador Sea, heat is transferred from the warmer...

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