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Tool of the Trade

Instruments like this, known as a CTD rosette, are a mainstay of oceanographic research. CTD stands for conductivity (which provides a measure of salinity), temperature, and depth. In this case, the actual CTD sensor is surrounded by a rosette of gray sample bottles mounted on a circular frame. As the entire instrument descends through the water, it transmits data back to the surface, where scientists and technicians watch a real-time display and decide where to collect water samples as the rosette rises back to the surface. CTD sensors (minus the sample bottles) can also be attached to moorings or to underwater vehicles. (Photo by Véronique LaCapra, Woods Hole Oceanographic Institution)