Instruments

Measurements are carried out from research vessels as POLARSTERN by lowering instruments with winches which measure water mass properties and transfer the data on board. Conductivity-Temperature-Depth probes (CTD) measure temperature and salinity on vertical profiles in the water column. Water samplers provide water from selected depths to determine the concentration of oxygen, CO2, nutrients, and trace substances.

Platforms which carry sensors are deployed from ships. They drift at the ocean surface or on sea ice and transmit location and data via satellite. Other systems (floats) sink to a prescribed depth level and follow the ocean currents at that level. They are tracked acoustically as SOFAR or RAFOS floats. Great emphasis is given to vertically profiling floats which measure between the surface and a certain depth temperature and salinity of the water column.

The floats are located and the data are transmitted by satellite when the floats reach the surface. To use such floats in ice covered areas, they need to avoid to be crashed in the ice when coming up to the surface, to be located under the ice when no satellite connection exists and to store the data until they can get back to the surface in an ice free area. The profiling floats contribute to the global Argo project. Sea gliders are floats which are able to follow a prescribed course and will be used to measure repeat transects.

Measurements at fixed locations are obtained by instruments moored at the ocean floor with anchors. The instruments record the data internally while moored. They have to be recovered with a research vessel after the end of the observation phase which can last for years, to obtain the data and to reuse the instruments. Systems which are able to transmit data from mooring to mooring and finally by a profiling transponder at the surface to satellites are under development.