The objective of this research is to study the role small-scale processes play on the circulation and water mass transformation in the Japan/East Sea (JES). The focus study area is the southwestern JES region where variability is especially energetic and affects the entire JES circulation. A field observational program has been planned for 2020/2021 that includes moored measurements in addition to ship-based profiling and autonomous observations. The in situ data will measure short and long-term turbulent and sub-mesoscale fluxes, bottom and pressure drags, and horizontal eddy diffusivities. The field data will then be analyzed to assess mixing variability, pressure fluctuations generated by lateral variation of bottom bathymetry, and to examine the dynamics of flow separation in the study area.