Oliver Zafiriou (left, holding rope) and crew of R/V Oceanus launch a water sampler on an October 1991 cruise. The shipboard instrument, known as a CTD for the fact that it measures conductivity, temperature, and depth, provides physical oceanographers with critical information about the water column, as well as unadulterated samples of water from depth. Work by oceanographer emeritus Neil Brown, Alvin Bradshaw and Karl Schleicher led to the invention of the first digital profiling instrument in the 1970s. Today, CTDs are deployed from research vessels worldwide.
(Photo by Craig Marquette, Woods Hole Oceanographic Institution)