CTD Rosette Test Cast

Today I finally figured out how the scientists and technicians actually take the measurements I’ve mentioned before... carbon levels, trace metals, alkalinity, helium and tritium levels, nutrients, etc. It’s a simple concept but the execution is quite involved: they lower a machine to great depths, and then they extract samples of water and bring them to the surface for testing. The goal is to obtain a large number of data points at different depths along the ship’s path in order to produce a large transect, a graphical cutaway of the ocean.



The CTD Rosette, as pictured, is a series of tubes, like the Internet. Also like the Internet, it weighs a lot, but unlike the Internet, the CTD rosette conveys water from ocean depths up to the surface. It weighs about 600 lbs. and can hold about 1500 lbs. of water. It’s quite an ordeal winching this behemoth up and down the water column, as you can imagine, but it’s also a pretty entertaining sight. After we perform this cast and recovery a hundred or so times, it might get old, but for now it’s great. ‘Great’ as in ‘large.’

The CTD rosette—CTD stands for Conductivity, Temperature, and Density, which are measured by on-board sensors—is designed to go down to 2000 meters below sea level and then draw water samples at regular intervals up to the surface. The procedure is difficult and is rigorously policed, since slight mistakes can contaminate water samples, or worse, damage the rosette. Jim Swift says the worst case scenario is if someone got hurt, but personally, I think that would sort of depend on who it was. Hm... it would also depend on how badly he or she got hurt, and whether it was his or her fault. For example, if a head-banging dude was banging his head to some heavy metal, and then banged his head on the rosette and broke a spigot, and if he was usually a jerk, and if banging his head didn’t cause any permanent damage, then I’d tell him: “You stupid idiot! I hate you!”