Line W is an array of five moorings that has been monitoring changes in two currents that play important roles in regulating Earth's climate: the Gulf Stream (orange area) and the Deep Western Boundary Current hugging the U.S. Eastern Seaboard. Line W aligns with the GUSTO mooring, which is monitoring the Gulf Stream, and Station S off Bermuda, where researchers have taken ocean measurements every two weeks since the 1950s.
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)
Line W has three moorings with profilers that travel up and down cables taking measurements of water salinity, temperature, and velocity. They are interspersed with moorings with sensors distributed along cables (including the GUSTO mooring). The moorings monitor the southward, cold Deep Western Boundary Current and the northward, warm, surface Gulf Stream, which act like an artery and vein in the North Atlantic Ocean circulation system. (E. Paul Oberlander, Woods Hole Oceanographic Institution)
Researchers prepare to attach a profiler, equipped with sensors to measure seawater properties, to a cable of a Line W mooring. A low-power motor propels the profiler up and down the cable every five days. (Jim Canavan, Woods Hole Oceanographic Institution)
WHOI physical oceanographer John Toole (Patrick Rowe, Woods Hole Oceanographic Institution)