Martha helping out with the CTD
Learning to Sample the CTD

Katie Gonzalez and Willem Weertman take water samples from the first CTD cast on the VISIONS17, OOI-NSF cruise. Credit: M. Elend, University of Washington.

A "CTD" rosette with a suite of attached sensors is utilized on Regional Cabled Array OOI cruises to measure ocean properties and to collect fluid samples adjacent to the Shallow and Deep Profiler Moorings for instrument verification. The rosette includes  conductivity-temperature-depth (CTD) sensors, dissolved oxygen, chlorophyll fluorescence, and a transmissometer to detect particles in the water column. During some cruises, these platforms also host a pH and Photosynthetically Active Radiation (PAR) sensor.  If time permits during the cruise, multiple vertical casts with the CTD package will be undertaken. Shipboard and follow-on shorebased analyses of fluids will be compared to the CTD on the ROV Jason and to instruments on the moorings to examine instrument calibration and drift. CTD's are conducted prior to recovery of instruments on the mooring, and subsequent to reinstallation.