An Autonomous Lagrangian Circulation Explorer (ALACE) float is an instrument that can be programmed to cycle up and down vertically through the water column at predetermined intervals, in order to provide vertical profiles of temperature and salinity.
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ALACE floats have been used to track currents down to depths of 1500 meters. In operation, the float sinks to its neutral buoyancy depth, drifts with the current, and after a programmed time (typically five to thirty days), the float increases its buoyancy by pumping oil into an external bladder to rise to the surface. It then transmits data to Service Argos satellites over a 24 hour period, returns the oil to the internal bladder, and sinks again to its neutral buoyancy depth. The cycling continues until the battery energy is depleted after around 100 cycles, or until the float fails for some other reason.