Principles of Oceanographic Instrument Systems -- Sensors and Measurements

For some purposes it is less important to measure the physical variables in the environment than to detect variations in them or to determine the pattern of those variations. The search for salt fingers illustrates this case. One ocean mixing process contending for the role of a major global process in 1972 was double diffusion, in particular salt fingering. But although there was indirect evidence for the widespread existence of salt fingers in the ocean, they had never been directly observed. In the laboratory, the most effective way to observe them was by optical shadowgraph, a technique that displayed the vertical pattern of the convecting cells. I used the same approach to detect them in the ocean.