Permalink : http://hdl.handle.net/2115/90256

JaLCDOI : 10.14943/bull.fish.73.1.1

KEYWORDS : Japan Basin Bottom Water (JBBW);Yamato Basin Bottom Water (YBBW);Benthic front;Numerical model experiment;Horizontal two-dimensional turbulent mixing

The benthic front of the Japan Sea has a distinct temperature difference and is formed at the boundary between the cold, hyperoxic Japan Basin Bottom Water (JBBW) and the hot, hypoxic Yamato Basin Bottom Water (YBBW).　The Previous study of Taya et al. (2022) found that the water mass classification of both bottom waters was determined using a dissolved oxygenpotential temperature diagram, and a remarkable mixing between the two bottom waters was formed near the tip of the JBBW, which entered the Yamato Basin from the Japan Basin side.　In order to investigate the water mass mixing process by the horizontal vortex flow, a numerical model experiment of nonlinear non-hydrostatic pressure in a rotating system was conducted using a simple jointed bottom front of JBBW and YBBW as the initial condition.　The baloclinic instability waves generated by small disturbances along the benthic front interact with each other nonlinearly and develop, leading to a two-dimensional horizontal turbulent flow near the front.　From this turbulent state, cold-water horizontal eddy currents (originating from JBBW) cascading up to 10 km scale were found to have a vortex-pair structure with a pair of positive and negative vorticity.　Furthermore, the Okubo-Weiss parameter is positive only on the positive vorticity side of the vortex pair (the rotational component is dominant over the strain component), and the uptake of external YBBW into the vortex flow is biased to this one side.　This may be the reason for the asymmetric water mass distribution observed in the horizontal vortex flow of the seafloor trapping.