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Images: Powerful Currents in Deep-Sea Gorges

The Mid-Atlantic Ridge undersea mountain range covers about half the floor of the Atlantic Ocean. Its flanks are lined with thousands of deep canyons like the one shown in the closeup below. (Map generated from Marine Geoscience Data System's GeoMapApp)

This canyon is one of hundreds running perpendicular off both sides of the Mid-Atlantic Ridge. Scientists have closely investigated this canyon and found a strong current flowing uphill along the canyon floor toward the ridge. Scientists think there are similar currents in many other seafloor canyons. Red and white dots indicate where sensors were deployed. (John Toole, Woods Hole Oceanographic Institution)

The seafloor is filled with thousands of deep canyons, where powerful currents appear to be flowing uphill along the canyon floors. These currents could play a major role in driving global ocean circulation. (Illustration by Jack Cook, Woods Hole Oceanographic Institution)

How can a current flow uphill on the seafloor? Water at the seafloor is stratified, with layers of progressively denser waters toward the bottom. Top diagram: When these layers collide with a slope, mixing occurs, and less dense waters end up at the same level as denser waters. Bottom diagram: Gravity then pushes the denser water to sink under the less dense water, driving a current flowing upward along the slope of the incline. (Jack Cook, Woods Hole Oceanographic Institution)

(Courtesy of Rebecca Walsh Dell)