FINE-STRUCTURE AND MICROSTRUCTURE CHARACTERISTICS ACROSS THE NORTHWEST ATLANTIC SUBTROPICAL FRONT

Vertical profiles of temperature, salinity, horizontal velocity, rate of dissipation of turbulent kinetic energy, and thermal variance are u sed to examine the parameterization of turbulent mixing associated wit h internal waves in an upper,ocean front. Previous attempts to quantif y the rate of turbulent dissipation [e.g., Gi egg, 1989; Polzin et al. , 1995] are based upon dynamical models of wave-wave interactions usin g the Garrett and Munk [1979] (GM) spectrum. Non-GM conditions (vertic al and horizontal anisotropy, deviations iii-vertical wavenumber and f requency spectral shapes, and the presence of a background flow) may a ffect the character of wave interactions, altering the upwavenumber en ergy flux, which is equated with the rate of turbulent dissipation; No n-GM conditions in the data are documented, and revisions to the wave- wave interaction models are discussed. Additionally, the strength of w ave-wave interactions is directly compared with the strength of wave-m ean flow interactions. These data indicate that the dissipation rate i s relatively insensitive to the presence of a background flow and anis otropic wave Conditions, in agreement with theoretical expectations ba sed upon wave-wave interaction models and a model of wave-mean flow in teraction at high background. Richardson number. These data support th e findings of Polzin et al. [1995], who argue that the dissipation rat e is most sensitive to variations in wave frequency.