A point source of heat in a stable salinity gradient

Abstract

When a salinity gradient is heated at a single point, a hot plume is formed with a series of layers around and above it in a ‘Christmas-tree’ flow pattern. Qualitative visual observations of the development of this system are reported. Three kinds of layers are observed: the first kind is formed above the basic plume from a hierarchy of secondary plumes on top of the basic one, the second develops around the upper part of the basic plume, and is driven by the same mechanism as the layers in sidewall-heating experiments, and the third, forming around the lower part of the basic plume, is of the same nature as the second type but also has something in common with double-diffusive intrusions. A characteristic feature for all the three kinds of layers is the existence of systematic shearing motions and vortices. Quantitative estimates for the plume height and the thickness of the layers are obtained.