Lagrangian analysis of the vertical structure of eddies simulated in the Japan Basin of the Japan/East Sea

Abstract

The output from an eddy-resolved multi-layered circulation model is used to analyze the vertical structure of simulated deep-sea eddies in the Japan Basin of the Japan/East Sea constrained by bottom topography. We focus on Lagrangian analysis of anticyclonic eddies, generated in the model in a typical year approximately at the place of the M3 mooring (Takematsu et al., 1999) and the hydrographic sections (Talley et al., 2001), where such eddies have been regularly observed in different years (1993)(1994)(1995)(1996)(1997)(1999)(2000)(2001). Using a quasi-3D computation of the finite-time Lyapunov exponents and displacements for a large number of synthetic tracers in each depth layer, we demonstrate how the simulated feature evolves of the eddy, that does not reach the surface in summer, into a one reaching the surface in fall. This finding is confirmed by computing deformation of the model layers across the simulated eddy in zonal and meridional directions and in the corresponding temperature cross sections. Computed Lagrangian tracking maps allow to trace the origin and fate of water masses in different layers of the eddy. The results of simulation are compared with observed temperature zonal and meridional cross sections of a real anticyclonic eddy to be studied at that place during the oceanographic Conductivity, Temperature, and Depth (CTD) hydrochemical survey in summer 1999 (Talley et al., 2001). Both the simulated and observed eddies are shown to have the similar eddy core and the relief of layer interfaces and isotherms.

Transport of FNPP1-derived radiocaesium from subtropical mode water in the western North Pacific Ocean to the Sea of Japan

“…This current meets the North Korean Cold Current, which is an extension of the Liman Cold Current. This northward-flowing warm, subtropical water meets southward-flowing cold, subarctic SOJ waters to form the polar front at approximately 40 • N. The SOJ is therefore divided largely into two regions (Prants et al, 2015). The current system in and around the SOJ should be taken into consideration when assessing the spatio-temporal variations in radiocaesium derived from global fallout and the FNPP1 accident.…”

“…Aeolian 137 Cs deposited south of the Kuroshio Extension was apparently subducted into the STMW and transported southwards within 10 months after the FNPP1 accident. Rossi et al (2013) have reported that simulated FNPP1-derived 137 Cs penetrated into the ocean interior via intense subduction and vertical mixing during the winter in the region of mode water formation as described by . Kamidaira et al (2018) have also reported that their model simulation reproduced relatively high 137 Cs activity concentration below the mixed layer.…”

Statistical analysis of Lagrangian transport of subtropical waters in the Japan Sea based on AVISO altimetry data

“…1) and the eastward zonal jet blocking northward transport across it. Topographically constrained anticyclonic eddies with the centre at about 41-41.5 • N, 134-134.5 • E have been regularly observed there (Takematsu et al, 1999;Talley et al, 2006;Prants et al, 2015).…”

Lagrangian Coherent Structures: A Climatological Look

“…Prants et al [31] explicitly look at LCSs near Japan, but they were looking at ocean current in the Japan Basin which is on the west side of Japan. This paper has references to people in Haller's group and mentions LCSs in the writing.…”