The vertical microstructure of temperature and salinity

Abstract

Measurements with a high resolution probe on a free fall vehicle have sensed temperature and salinity fluctuations in the millimeter range and permitted calculation of the vertical density profile to scales of 2 cm. Observations between 210 and 340 m off San Diego show that features larger than several meters are stably stratified, implying that the numerous temperature inversions must be formed by lateral advection. The temperature inversions have been resolved into several gravitationally stable layers separated by sharp interfaces a few centimeters thick. These sharp steps of increasing temperature and salinity are attributed to the instability which results from the differential diffusion of heat and salt across an interface formed by warm saline water underlying colder fresher water. Numerous instabilities have been found with length scales less than 1 m and continuing down to the limit of resolution of Väisälä's frequency. Features of another type are suggestive of local overturning driven by mechanical forces. © 1972.