Global mapping of diapycnal diffusivity in the deep ocean based on the results of expendable current profiler (XCP) surveys

Abstract

Based on the results of the extensive XCP surveys in the North Pacific, we first examine the empirical relationship between the estimated diapycnal diffusivity in the thermocline and the numerically predicted, available energy density of the semidiurnal internal tide (major energy source for diapycnal diffusivity) at each location. The diapycnal diffusivity is estimated by applying the parameterization of Gregg (1989) to the fine‐scale vertical shear of horizontal velocity measured by XCP. Next, the numerically predicted energy density of the semidiurnal internal tide at each longitude and latitude in the world's oceans is incorporated into the resulting empirical relationship to obtain the global distribution of diapycnal diffusivity in the thermocline. This model predicts that strong diapycnal mixing (mixing hotspot) is limited to the prominent topographic features at latitudes between 20° and 30°.