A discussion on ocean currents and their dynamics - The thermocline problem

Abstract

The main, oceanic thermocline, the layer of strong vertical temperature and salinity gradients in the ocean, and the region below this, where the water asymptotically approaches the deep-sea state, is still far from explained. There have appeared a series of theoretical studies of this phenomenon in recent years, starting with a linearized model by P. S. Lineykin and later concentrating on the nonlinear problem retaining the important nonlinear density advection. A summary of the work up to 1969 has been given by Veronis (1969). It must be admitted that we are still uncertain even about the basic mechanism of the main thermocline. There appears to be several reasons for such an uncertainty. First, we have few direct measurements of horizontal velocities, and none of vertical velocity and vertical turbulent diffusion of heat and salt in the thermocline. The vertical velocities are so small, of order lO-5 cm/s that no known instrument can feel them.