Diapycnal Mixing and Double Diffusion over the Continental Slope in the Northern Sea of Japan in the Warm Half-Year

This article is devoted to an analysis of double diffusion processes responsible for diapycnal mixing in the zone of the westward Primorye Current in the northern part of the Sea of Japan. This article presents the results of processing and analysis of a long time series of regular measurements of vertical profiles of thermohaline characteristics and current velocity over the upper part of the continental slope between the depths of 60 and 420 m using the Aqualog mooring station from April to October 2015. Efficient heat and salt exchange coefficients and the buoyancy flux are estimated using the Osborne-Cox (1972) and Gregg (1989) parameterizations. The Turner angle for the verification of double diffusion processes is estimated. The contributions of diffusive convection and salt fingers to the buoyancy flux are studied. It is established that, due to differential diffusion, the layer from 80 to 170 m was involved in intense vertical mixing. Moreover, from midspring to early May, diffusive convection penetrates to a depth of 250 m, and then a process like salt fingers plays a leading role. Shear instability, caused, among other processes, by the weakly nonlinear interaction of internal waves, prevails in the underlying layers.

Automated summary

This article analyzes the double diffusion processes in the zone of the westward Primorye Current in the northern part of the Sea of Japan. The study examines the thermohaline characteristics and current velocity profiles using data collected from April to October 2015. The results show intense vertical mixing in the 80 to170-meter depth range due to differential diffusion, with a shift to diffusive convection and salt fingers at depths below 250 meters.