What do we measure and how?

  • CTD Rosette

    CTD Rosette

    Perhaps the most commonly used tool in oceanography is the CTD rosette. The rosette primarily houses a Seabird CTD to measure the variation with depth of the fundamental water properties of temperature and conductivity. The metal frame is lowered throughout the water column, typically from the surface all the way to the bed at potentially thousands of meters depth.

    In addition to the range of sensors that accompany the CTD, such as dissolved oxygen and chlorophyll, are 24 Niskin water bottles that each obtain 20 litres of water from depths that we choose. As the frame is winched back to the surface, we wait for one minute at each depth from which we wish to obtain a sample of water and then close the bottle remotely from the ship. This water is then collected from the bottles on deck and analysed for properties like nutrients, oxygen and other gases. During JR311 we have been obtaining nutrient samples to determine the role of the eddy and submesoscale instabilities in supplying nutrients to the surface layers.