Friday, June 4, 2010

Day 37 - CTD

Characterisation of the marine mammal habitat plays an important role in the understanding and interpretation of the visual and acoustic observations. The instruments used during Sirena 10 allow us to measure not only the traditional oceanographic parameters such as pressure, temperature and salinity, but also how the water column affects the propagation of light. Additional parameters such as oxygen and chlorophyll concentration further extend our knowledge of the marine environment.

Three main systems are used for these measurements. Today we talk of the CTD.

The CTD consists of a metal frame with multiple sensors attached to its struts. It is lowered into the water on a cable which also allows the electrical transmission of the data to the laboratory in real-time. In addition to the sensors, bottles are used to collect water samples for later chlorophyll analysis. During Sirena10, profiles were collected down to 1500 metre depth (see the picture for a typical profile). Timing of the casts coincides with satellite overflights, allowing offline comparison of remotely measured surface temperature and chlorophyll concentration.

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