Surface to the Ocean Floor Survey with the CTD-Rosette

By Anne-Sophie Fortin

Conductivity Temperature Depth (CTD) and sampling from Niskin bottles.
Left: The CTD-Rosette is on the deck, ready to dive to the ocean floor. Right: Paula and Elizabeth are sampling seawater from the Niskin bottles. The temperature of the seawater sampled is very cold for our hands (it can be as low as -1oC).

As we move along the 53oN Array, we are performing “CTD casts” which consist of lowering a CTD-Rosette to the ocean floor and pulling it back up on deck. A CTD is an instrument that precisely measures the Conductivity and Temperature at every Depth. We can then compute the salinity from the conductivity and the temperature. A Rosette samples seawater at selected depths in so-called “Niskin bottles”. From an analysis of the seawater, we can determine the concentration of nutrients, salt, dissolved oxygen, and dissolved inorganic carbon.

The CTD casts also serve to calibrate the moored instruments of the 53oN Array. To do so, we attach the instrument to the CTD-Rosette in between their recovery and deployment. The pair of datasets that are generated by the instruments belonging to the 53oN Array and the CTD is then used for the instrument calibrations.

Koordinaten: 53.195, -50.627167

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