Turbulent mixing brings nutrients into the surface layer from below so that plankton can grow. Turbulence near the surface, driven by surface winds and cooling, transmits heat in and out of the ocean to create the reservoir of heat that governs climate. Turbulence in the bottom layer affects the deposition, resuspension and movement of sediments. Turbulence creates micro-environments for the small creatures that form the basis for life in the oceans.
Turbulence is the irregular, random component of fluid motion.
Its spatial scales are usually the smallest scales of the flow. The turbulence we shall discuss is the 0.01 to 10-meter overturning motions that result in vertical transport and mixing. Turbulent motions in a stratified fluid intermingle fluid parcels from different parts of the flow, thereby enhancing mixing across concentration gradients by molecular diffusion. But to understand the mixing, we have to deal with the messiness of turbulence. Further, since turbulent motions are rapidly dissipated in the absence of an energy source, it is probably rare that we observe steady-state turbulence.