Residual Overturning Circulation and Associated Water-Mass Transformation in the East/Japan Sea.

(Kim, Y., Song, H., Han, K., An, S., Park, y., and Marshall, J.), Journal of Physical Oceanography, vol. 55, no. 5, pp. pages, 2025.

Abstract

The East/Japan Sea (EJS), a marginal sea in the northwest Pacific, has marked isopycnal slopes, especially during winter, implying a store of potential energy available for baroclinic instability and hence, perhaps, a significant role for eddy processes in shaping the residual (mean plus eddy) overturning circulation. Here, for the first time, we compute the residual overturning circulation in the EJS in a high-resolution simulation and relate it to water-mass transformation processes due to air–sea fluxes and interior mixing. A sizable eddy-driven circulation is indeed found in the vicinity of tilted isopycnals. Wintertime surface buoyancy loss facilitates a volume flux toward higher-density classes, with latent heat loss being the main contributor and sensible heat loss also playing a role. The densification of northward subsurface flow is associated with diapycnal mixing. The water-mass formation rate, derived from the transformation rate, identifies upwelling and downwelling to the south and north of the subpolar front near 39.5°N, respectively, consistent with the broad pattern of residual overturning circulation.

doi = 10.1175/JPO-D-24-0100.1