Observations of the “salt fountain”

Abstract

Data collected with the submarine USS Dolphin off San Diego in April 1982 show temperature and salinity decreasing monotonically from the surface downward, with temperature dominating density by a factor of 10. The ocean is turbulent to 0.5‐m depth with descending cells of water (0.04 to 0.08 m in diameter) emanating from that region and extending to 3‐m depth in quiescent water. The return, upward, flow is more dispersed and hence the flow pattern, and the small‐scale temperature gradient signal is not symmetrical. These features are the salt fountain of Stommel et al. (1956).The phenomenon was observed on two separate days, always during calm weather, but only between 1000 and 1200 local time. Although the cells are often found in groups, one also finds individuals well separated from the others. These features are reminiscent of the solutions for buoyant convection from a thin layer into an infinite region. Perhaps these cells are more appropriately understood in terms of the time‐dependent instability problem, rather than in terms of a spatially sinusoidal, eigenvalue problem.Examination of data from the thermocline shows similar features imbedded in the regular temperature gradient signal that is normally associated with salt fingers. © 1991 Taylor & Francis Group, LLC.