HOW FLOATS WORK

The idea beneath the oceanographic use of deriving platform to sample the water column is to overpass limitation in sampling due to ship costs, sea-weather conditions, geographical limitations and ultimately the use of human resources. Nowadays floats offer the most cost-effective solution to this needs. The oceanographic data are collected by battery-powered autonomous floats that spend most of their life drifting at depth where they are stabilized by being neutrally buoyant at the "parking depth" pressure by having a density equal to the ambient pressure and a compressibility that is less than that of sea water.

Figure 2. Scheme of the operation of the floats in the sea.

At present there are several models of profiling float. All work in a similar fashion but differ somewhat in their design characteristics. At typically 10-day intervals, the floats pump fluid into an external bladder and rise to the surface over about 6 hours while measuring temperature and salinity. Satellites or GPS determine the position of the floats when they surface, and the floats transmit their data to the satellites. The bladder then deflates and the float returns to its original density and sinks to drift until the cycle is repeated. Floats are designed to make about 150 such cycles.