Mon, 02/27/2017 - 12:20pm 261 Marine Science Bldg. Seminars Athens Events Mixing by turbulent motions in the ocean is important for global ocean circulation, nutrient supply to surface waters, and the global ocean heat budget. Turbulent mixing takes the form of a diffusive process where the vertical flux is proportional to the concentration gradient with an eddy diffusivity coefficient, Kz, as a constant of proportionality. Osborn (1980) suggested that Kz is in turn related to the flux Richardson number (Rif) or mixing efficiency (G) that is commonly assumed to be a constant value of 0.2. However, recent observations have suggested a dependence of Rif on a variety of other parameters. Here, I discuss direct measurements of the buoyancy flux (and hence the mixing efficiency), the dependence of Rif, and examine the implications of a variable mixing efficiency on current estimates of mixing in the ocean.