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Images: Detours on the Oceanic Highway

In the past decade, scientists Amy Bower of WHOI and Susan Lozier of Duke University have used floats to observe that some southward-flowing waters may detour out of the Deep Western Boundary Current. One potential detour spot may be at the Grand Banks of Newfoundland, where the coastline takes a series of sharp turns. (Eric S. Taylor, WHOI Graphics Services. Base map from NOAA)

The ocean’s global circulation transports heat around the planet, from the equator to the poles, thus regulating Earth’s climate. Two major cogs in this planetary heating and ventilation system are the Gulf Stream-North Atlantic Current, which brings warm waters toward the Arctic, and the Deep Western Boundary Current, which carries cold waters south toward the equator. Line W is an ocean observatory system strategically placed across across the DWBC and close to the Gulf Stream. (Jack Cook, WHOI Graphics Services)

As recently as the early 1960s, without instruments to investigate deep ocean circulation, nobody knew that the Deep Western Boundary Current existed. Two scientists at Woods Hole Oceanographic Institution (WHOI), Henry Stommel and Arnold Arons, used a theoretical model to explore deep-sea circulation. They calculated the essential physical forces acting on the flow of water in bounded basins on a rotating sphere. Their calculations suggested the existence of the Deep Western Boundary Current. A few years later, English oceanographer John Swallow and Val Worthington at WHOI placed floats in the ocean to confirm the prediction. (Arnold Arons and Henry Stommel, WHOI)

Since 2004, WHOI scientists have maintained Line W, a series of six moorings that starts at the continental slope off Cape Cod, Mass., and heads southeast. Line W is strategically placed to continuously monitor the southward-flowing Deep Western Boundary Current. Scientists also measure the northward-flowing Gulf Stream once a year by taking measurements farther to the southeast. (John Toole and Ruth Curry, WHOI)

Line W Moorings consist of cables as tall as ten Empire State Buildings. The cables are anchored to the ocean floor and held upright by buoyant glass spheres. Instruments ride up and down along the cables, measuring the temperature, salinity, depth, and velocity of the water as it flows by. (E. Paul Oberlander, WHOI Graphics Services)

To explore why waters may be exiting the Deep Western Boundary Current, Isabela Le Bras is using a mathematical model that focuses on three features: the Deep Western Boundary Current, the topography off the Newfoundland coastline that affects it, and the Gulf Stream. Equations in the model simulate the dynamics of the ocean and generate eddies. By conducting numerical experiments and manipulating the strengths and configurations of the three key features, she can see which factors cause diversions from the Deep Western Boundary Current.

(Jack Cook, WHOI Graphics Services)