Séminaire
Turbulence in both the ocean and atmosphere is an important contributor to the mixing and transport of properties such as momentum, heat, salt and water vapour. In the stably stratified parts of the fluid flow the turbulence is often intermittent and patchy making sampling the process and determining its impact difficult. An exception is the Western Equatorial Pacific which proves to be an ideal natural laboratory to study shear-generated turbulence. Here turbulent production is dominated by the shear associated with relatively long-lived flow structures in the form of small vertical scale inertia-gravity waves and flow instabilities. With enough vertical resolution we can directly measure the characteristics of these flow features. We find a strong relationship between the vertical shear, stratification and the turbulent activity and the implied vertical diffusion coefficient. In addition our observations indicate that the scaling of the vertical mixing length scale is consistent with theory and numerical studies. We will discuss the implications for the large-scale interactions of the tropical ocean and atmosphere such as El Niño, and more generally improvements to the way the effects of turbulence are incorporated into models used to study the Earth's climate.