Turbulent length scales in a fast-flowing, weakly stratified, strait: Cook Strait, New Zealand

There remains much to be learned about the full range of turbulent motions in the ocean. Here we consider turbulence and overturn scales in the relatively shallow, weakly stratified, fast-flowing tidal flows of Cook Strait, New Zealand. With flow speeds reaching 3 m sinline-formula⁻¹ in a water column of inline-formula∼300 m depth the location is heuristically known to be highly turbulent. Dissipation rates of turbulent kinetic energy inline-formulaε, along with the Thorpe scale, inline-formulaL_T, are described. Thorpe scales, often as much as one-quarter of the water depth, are compared with dissipation rates and background flow speed. Turbulent energy dissipation rates inline-formulaε are modest but high for oceans, around inline-formula $M6inlinescrollmathml\mathrm{normal\; 5}\times {\mathrm{normal\; 10}}^{-\mathrm{normal\; 5}}$ 42pt13ptsvg-formulamathimg691fa10b2fad75855918d92d4b564c62 os-14-801-2018-ie00001.svg42pt13ptos-14-801-2018-ie00001.png  W kginline-formula⁻¹. Comparison of the buoyancy-limit Ozmidov scale inline-formulaL_Oz suggest the Cook Strait data lie for the majority of the time in the inline-formulaL_Oz > inline-formulaL_T regime, but not universally. Also, comparison of direct and inline-formulaL_T-based estimates of inline-formulaε exhibit reasonable similarity.