Energy Dissipation and Upwelling in a Western Boundary Current

Abstract

Abstract Energy dissipation in a western boundary current begins with the conversion of mean potential energy into kinetic energy of “primary” eddies. The rate of this energy conversion is taken to equal the total energy dissipation rate, in analogy with the energy cascade of laboratory turbulence. The growth of primary eddies is due to baroclinic instability, and implies the rising of relatively light fluid, sinking of heavy fluid. An inviscid, nondiffusive model adequately describes this process and yields a quantitative relationship between the dissipation rate and upward-downward motions. In statistically steady flow, an eddy mass transport arises from the correlation of cross-stream velocity and isentropic layer thickness which is proportional to the energy dissipation rate. In this manner, the rate of upwelling of upper thermocline fluid and/or the downwelling of heavier fluid comes to determine the energy dissipation rate. Conversely, a given energy dissipation rate implies upwelling or downwelling...