The Instrument To Know
It’s the workhorse instrument of the physical oceanographer. It’s the first thing into the water at every sampling station. It has its very own room on the ship. Ladies and gentlemen, I present the CTD.
The “T” and “D” stand for temperature and depth. The “C” is for conductivity, a way to measure saltiness, or salinity. The CTD’s job is to make those measurements as it’s lowered through the water. At any one station, the information that comes back from the CTD isn’t all that interesting, says Ned Cokelet, an oceanographer at the National Oceanic and Atmospheric Administration. “But when you put them on a whole line, you can paint a picture of the ocean.” These are the things physical oceanographers are interested in: the physical characteristics of the ocean. But biologists use those measurements, too.
The CTD sits on a rosette, a big round frame with bottles that can be tripped by an operator on board to collect water. This water goes to all sorts of experiments and tests. Some people take the water to feed to organisms in experiments. Some take samples to measure the nutrients or chlorophyll in the water, which helps scientists understand what the ocean is like for animals and plants to live in.
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