Turbulence observations using moored temperature sensors in weakly stratified deep West-Mediterranean waters

Abstract

In the stably stratified ocean, small-scale turbulence is important for vertical exchange and hence for the mixing of water masses and suspended matter. To observationally study turbulent motions and the buoyancy- and shear-generators behind them, a 100-m tall array of high-resolution temperature (T) sensors was moored at a 2480-m deep seafloor near the steep continental slope of the Western Mediterranean Sea. The area is dominated by boundary flow, (sub-)mesoscale eddies, internal waves, wintertime dense water formation, and very weak vertical density stratification. Various physical oceanographic processes are observed in detail through a seasonal cycle, including: Low shear-driven turbulence in weak stratification in late-summer and autumn, large buoyancy-driven turbulence by geothermal heating from below alternated with inertial internal wave motions in winter, and moderate buoyancy-like turbulence pushed with stratified waters from above in late-winter and spring.