The Physical Nature and Structure of Oceanic Fronts V19

Published by the American Geophysical Union as part of the Lecture Notes on Coastal and Estuarine Studies Series, Volume 19.

During the past several years, research into the frontal divisions of the ocean has been particularly intensive. The significance of this lies not only in the fact that, in the five years from 1976 to 1980, more than 500 papers on this question were published in various journals throughout the world and at least three major international discussions were held (see p. 17). The newness of the discussion of the topic steins from the qualitative reinterpretation of the physical essence of the phenomenon and its role in the ocean, particularly in the processes of mixing and structure formation.

While in the past the conventional view of fronts as boundaries between large-scale water masses of the ocean only led to the recognition of convenient classification limits created by nature itself, there is now a tendency to study oceanic fronts as integral elements of the dynamics of oceanic waters. As we understand it, fronts are being associated more and more with the dynamic and kinematic features which arise when kinetic energy and enstrophy are transmitted through a cascade of scales characterizing various forms of motion of a stratified medium in laterally confined oceanic basins. We are beginning to get a better understanding of the role synoptic-scale oceanic eddies play in the process of frontogenesis in the ocean. We are beginning to perceive the laws that govern the creation and destruction of fronts due to sudden disruption of the normal processes which match the response of the ocean to the fluxes of heat and buoyancy across the ocean/atmosphere boundary. We can no longer ignore the role of the Earth's rotation in the formation, maintenance and evolution of fronts, as well as in the development of instability at these fronts. Finally, we are turning to fronts as the most likely, and possibly the most effective mechanism for mixing and the transfer of heat and salt through the hydrostatically stable pycnocline. We no longer doubt that the link between the vertical finestructure of the ocean and mesoscale horizontal inhomogeneities inevitably involves fronts.