Line W monitors currents at a critical junction in the global circulation of the oceans.
In the tropical Atlantic, intense sunlight warms the ocean, while dry Trade Winds cause surface waters to evaporate and become saltier. The Gulf Stream carries this warm, salty water north along the U.S. East Coast and then toward Europe, before it transitions into the North Atlantic Current and heads north. As this water reaches higher latitudes, it releases heat to the atmosphere, tempering winters in the North Atlantic region and leaving behind saltier, cooler, and denser waters.
These transformed waters sink to the depths and form the Deep Western Boundary Current, which flows southward along the East Coast—beneath the northward-flowing Gulf Stream—and into the South Atlantic. This process of sinking and southward flow draws more warm water northward to replace it and contributes to a worldwide circulation pattern sometimes referred to as the “Ocean Conveyor. (E. Paul Oberlander, Woods Hole Oceanographic Institution)[back]
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