On the structure of salt fingers

Abstract

The structure of fingers in heat-solute system is investigated in the laboratory. In particular, the velocity of the fluid in the fingers and the horizontal and vertical length scales of the fingers, which form at the interface between two layers with the upper layer having an excess of the heat and solute but still less dense than the lower layer, are measured and related to the temperature and solute concentration differences across the interface. Dimensional analysis is used to predict the way the details of the finger motions depend upon the properties of the well-mixed layers on either side of the interface. The experimental results are found to be in agreement with these predictions. The laboratory data are then extrapolated in order to provide estimates for the size and velocity of salt fingers in the ocean, using data appropriate to the layered microstructure found beneath the Mediterranean outflow by Howe and Tait (1970).