UC San Diego

Small-scale turbulent mixing in the ocean is an important piece in many larger scale questions in ocean physics and climate. Measurements that can resolve the details of these centimeter and meter scale dynamics are often demanding to undertake, and typically not practical for addressing questions posed on regional and global scales. Here we utilize the global Argo array of profiling floats, and a previously developed finescale method for approximating the open ocean dissipation rate, to produce 800,000 estimates of this value distributed throughout the ocean. We show that average profiles calculated using this finestructure method agree with average microstructure profiles at the same location within a 2-3 for 96% of the comparisons. This indicates that it is a viable method for exploring large-scale patterns of ocean mixing. The near global maps of the average dissipation rate we generate indicate that the values are spread over multiple orders of magnitude, and that there are distinct spatial patterns present. These spatial patterns are correlated with seafloor roughness, near-inertial kinetic energy, tidal kinetic energy, and eddy kinetic energy. Dissipation rate estimates are also elevated in the equatorial band. The correlation to eddy kinetic energy is not observed to be related to the proximity to a particular eddy, nor the sign of the vorticity of that eddy, but it is correlated with the magnitude of the velocity of the nearest eddy. In zonally averaged profiles a seasonal cycle of a factor of 2-5 is observed beneath storm tracks, especially between (30-40 degrees) in both hemispheres. This seasonal cycle extends to the full depth of our 2000 m measurements and has a larger amplitude in places with strong eddy kinetic energy. Our observations suggest that this could be caused by a modulating effect of stronger eddy kinetic energy regions on the near-inertial energy flux from the winds at the surface into the thermocline.