RAFOS Floats: Defining and Targeting Surfaces of Neutral Buoyancy

Abstract

Abstract For timescales much greater than the local buoyancy period, the buoyant response of a RAFOS float is virtually dictated by its compressibility. As the compressibility of a thermally inert RAFOS float increases from zero, its oceanic equilibrium surface undergoes a smooth continuous deformation starting from an in situ density surface, eventually merging with an isopycnal surface and finally with a neutral surface. Thus there is a continuum of operational modes available to RAFOS floats; each mode is associated with a critical compressibility. Hypothetically, the compressee that transforms an isobaric RAFOS float into an isopycnal float can be modified to make a neutral-surface drifter by altering the critical value of its compressibility. The ballast procedure used to target a float to a prescribed equilibrium surface can be viewed as an accurate (±3%) laboratory measurement of the float's compressibility. For current “isobaric” RAFOS floats, the mean measured compressibility was approximately 2....