Simulation and Validation of Submesoscale Dynamics in the East/Japan Sea Using MOM6

The East/Japan Sea (EJS) is a semi-enclosed marginal sea in the Northwest Pacific Ocean, characterized by oceanographic features typically associated with large-scale systems, such as thermohaline circulation, submesoscale eddies, subpolar front, and intermediate water formation. Submesoscale eddies frequently form along the ESJ polar front, playing a crucial roles in large-scale processes, including turbulent ocean mixing, surface nutrient transport, and the support of chlorophyll blooms. Despite its significance, large portions of the EJS remain underobserved, leaving gaps in our understanding of its complex dynamics.

We present the establishment and evaluation of the high-resolution (1/48 ˚) East Sea regional model using MOM6, the latest version of the Modular Ocean Model (MOM) developed by GFDL to capture the submesoscale dynamics. The model was designed with a spatial resolution of approximately 2km (1/48 ˚) and employs a hybrid vertical coordinate system. High-resolution (1/24˚) Northwest Pacific Ocean reanalysis (KOOS-OPEM), which reliably reproduces the characteristics of the EJS, were used for the initial and open boundary conditions.

We investigated the variability in the separation latitude of the East Korea Warm Current (EKWC), a western boundary current in the EJS, under different wind forcing datasets. For this analysis, we used the ERA5 dataset from ECMWF, featuring a horizontal resolution of approximately 31 km and a temporal resolution of 1 hour, as well as the UM model data from the Korea Meteorological Administration, which offers a higher horizontal resolution of approximately 12 km and a temporal resolution of 6 hours. In addition, to validate submesoscale processes, the kinetic energy spectrum was then calculated via the Discrete Fourier Transform (DFT) and systematically evaluated.

This study provides significant insights into the submesoscale dynamics of the EJS and establishes a robust foundation for advancing regional ocean modeling efforts.