Evaluation of spatial distribution of turbulent mixing in the central Pacific

A long-term mean turbulent mixing in the depth range of 200-1000m produced by breaking of internal waves across the middle and low latitudes (40 degrees S-40 degrees N) of the Pacific between 160 degrees W and 140 degrees W is examined by applying fine-scale parameterization depending on strain variance to 8-year (2005-2012) Argo float data. Results show that elevated turbulent dissipation rate (epsilon) is related to significant topographic regions, along the equator, and on the northern side of 20 degrees N spanning to 24 degrees N throughout the depth range. Two patterns of latitudinal variations of epsilon and the corresponding diffusivity (K) for different depth ranges are confirmed: One is for 200-450m with significant larger epsilon and K, and the maximum values are obtained between 4 degrees N and 6 degrees N, where eddy kinetic energy also reaches its maximum; The other is for 350-1000m with smaller epsilon and K, and the maximum values are obtained near the equator, and between 18 degrees S and 12 degrees S in the southern hemisphere, 20 degrees N and 22 degrees N in the northern hemisphere. Most elevated turbulent dissipation in the depth range of 350-1000m relates to rough bottom roughness (correlation coefficient=0.63), excluding the equatorial area. In the temporal mean field, energy flux from surface wind stress to inertial motions is not significant enough to account for the relatively intensified turbulent mixing in the upper layer.