“Turbulent mixing” in a salt finger staircase

Abstract

Towed thermistor chain measurements are examined for patches of “turbulent mixing” occurring within salt finger interfaces in the Caribbean staircase (the Caribbean Sheets and Layers Transects (C‐SALT) experimental area). Patches are identified as regions having short overturning internal waves, resembling Kelvin‐Helmholtz billows, and higher‐wave number, more random fluctuations. For a patch turbulent dissipation rate of ≈ 2×10−8 W kg−1 (based on other C‐SALT measurements and consistent with the observed billow heights of 2–5 m) and an observed patch occurrence of ≈1%, the mean dissipation rate is ≈ 2×10−10 W kg−1. This amount of turbulence would increase the buoyancy flux of heat and salt by 10–20% over fluxes from fingers acting alone and would increase the flux ratio by about 10% to 0.83, close to the value inferred from conductivity‐temperature‐depth data by Schmitt et al. (1987).