During the Polarstern cruise ANT XVIII/2 we investigated within the scope of the iron fertilization experiment EISENEX the mixing regime of the upper 150 meters of a mesoscale eddy in the vicinity of the Antarctic Polar Front (APF) at 47°S and 21°E. On the basis of hydrographic CTD and ADCP profiles we deduce the vertical diffusivity K from two different parameterizations. To investigate the vertical mixing within the eddy that might be associated with elevated shears from internal waves, we use the parameterization of Gregg (1989). To check these results we use a parameterization of mixing processes by means of coefficients of eddy mixing that are dependent on the Richardson number, which was deduced after Pacanowski and Philander (1981). Since these parameterizations bear the character of empirical functions, which base on theoretical and idealized assumptions, they were inter alia compared with Thorpe scale related diffusivities deduced from MST measurements, which supplied the first direct insights into turbulence of this ocean region.