Upper ocean mixing from shear microstructure and density inversions nearthe Walvis Ridge

<p>The M180 cruise is part of the observational program of the TRR 181 'Energy Transfers in<br>Atmosphere and Ocean', and will focus on observe numerous energy compartments in<br>order to construct a regional oceanic energy budget for the southeast Atlantic. The study<br>area will be nearby the Walvis Ridge, a region of strong eddy activity and internal tides, in<br>the Eastern South Atlantic (0&#8192;-10&#8192;E, 30&#8192;-35&#8192;S). There, energy is converted from barotropic<br>to baroclinic tides at the seafloor. Additionally, in this region, the Agulhas leakage regularly<br>sheds eddies from the Agulhas current in the form of Agulhas rings that propagate slowly<br>northwestward. The location is, therefore, ideal for the study of interaction and links<br>between different energy compartments in the ocean and at the ocean-atmosphere<br>boundary.<br>The work will focus on energy dissipation and diapycnal mixing which, on the smallest<br>scales, drive the circulation in the ocean and is thus of highly significant for the global<br>meridional overturning circulation in the ocean and its deep ventilation. Time series<br>microstructure stations will be used to assess locally the temporal variability of mixing<br>and dissipation. From temperature, density and shear profiles obtained with a Vertical<br>Microstructure Profiler (VMP-250-IR), it will be possible to calculate the energy dissipation<br>rate of turbulent kinetic energy by assuming a statistically valid linear relationship<br>between the Thorpe Scale and the Ozmidov Scale. A direct comparison between the<br>inferred estimation of the dissipation rate and the directly calculated dissipation rate will<br>be presented. Moreover, in case a possible influence from Agulhas rings on dissipation is<br>detected, it will be investigated.</p>