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Float activities within MerSea


Why Float Observations? How does it work? Deployment and Scientific results: 1- Nordic Seas 2- Atlantic Ocean 3- Southern Ocean	Provor Float equipped with a Seabird salinity sensor

How does a float work?

The new generation of profiling floats are freely drifting devices, that every ten days measure a profile of temperature and salinity (and sometimes other parameters) in the upper 2000 m of the water column. In between profiling the floats drift at pre-set depth levels. Data are transmitted ashore via satellite when the float is at the sea surface.

How do the floats stay at depth?
The floats are developed from an invention made by a British scientist, John Swallow, in the 1950s. They have a “pressure case” that contains electronics and batteries. Seawater is compressible (as the pressure increases with depth, so the water density increases). The pressure cases are less compressible than seawater and are heavy enough to just sink when they are put in the ocean. As they sink they gain buoyancy so that at some depth, that can be calculated, the density of the float equals the density of the water and so they stay at that level.

How do they go up and down?
When it is time for the float to surface a pump moves oil from inside the pressure case to a bladder on the outside. The bladder inflates and increases the volume of the float, the float’s mass remains the same so its density decreases and the float rises. When it is time for the float to dive again the oil is drawn back into the pressure case. The floats are battery powered.