Internal oceanographic microstructure phenomena

Abstract

This paper is concerned with the nature and causes of both fine structure and microstructure in the ocean. Following an account of the acoustic/oceanographic background to subject, the characteristics of fine structure are described in terms of temperature and salinity profiles from the N.E. Atlantic. The three main causal mechanisms, horizontal advection, shear instability and double diffusion are discussed and their relative importance to fine scale phenomena is assessed. Microstructure observations from high resolution free fall instruments are used to illustrate the main features of the true microscale. These data provide evidence for the presence of both shear instability and double diffusive mechanisms. An examination of the relationship between the fine and micro scales leads to the conclusion that within an otherwise "quiet" ocean intensive vertical mixing occurs sporadically in specific areas characterized by the presence of an appreciable fine structure.