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.

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.

During a data collection and reporting cycle, a PALACE (Profiling Autonomous LAgrangian Circulation Explorer) float drifts with the current at a programmed depth, rises every week or two by inflating the external bladder (recording temperature and salinity profiles on the way up), spends a day at the surface transmitting data, then returns to drift at depth by deflating the bladder. Source: Woods Hole Oceanographic institute

Further Reading

• Seas of the World on Encyclopedia of  Earth
• Physical Oceanography Index
• R. E. Davis, D. C. Webb, L. A. Regier, and J. Dufour. The autonomous lagrangian circulation explorer (alace). J. Ocean and Atmosph. Tech., 9:264–285, 1992.