This is how we do it

We use a Rosette to collect water samples and take CTD/LADCP profiles at many stations in the Pacific Ocean along 30°N from Hawaii to California. The Rosette, kindly referred to as Rosy, has 36 Niskin bottles around its brain (carousel) and a number of sensors at the bottom. Here, after diving 5900 meters to the bottom of the ocean, our Rosy is gloriously coming back from her journey to the deep sea.

Our CTD team welcomes her aboard and helps out by dragging her with hooks and tag lines. Once on board, she is being railed back to its home where a team of scientists is waiting to collect ocean water samples from the Niskin bottles, which were tripped at different depths. The water samples are needed to measure the chemical composition of water to infer, for example, the CO₂ cycle in the ocean – an important factor driving the climate variability. These are time consuming laboratory measurements that cannot be done in-situ. In turn, the data collected from the sensors is sent over the wire to the ship's main lab where it is recorded and visualized in real-time during the cast.

The CTD sonde has sensors measuring Conductivity, Temperature and pressure (that gives us Depth). Other sensors include the transmissometer measuring water clarity, dissolved oxygen - O₂ concentration, and fluorometer - tiny biomass. The altimeter (green box) is used to precisely determine the distance to the ocean floor so that the Rosette doesn't hit the bottom as it goes down - the sensors are very sensitive and we don't want to damage them. The yellow cylinder with blue bottom is the Lowered Acoustic Doppler Current Profiler (LADCP), which measures strength and direction of ocean currents.

by Yeping and Georgy