167 / 2024-09-10 15:16:14

Submesoscale eddies along the continental shelf break in the East China Sea: their characteristics and mechanism, simulated by the MaCOM model

submesoscale eddies,Kuroshio,East China Sea,MaCOM

As the Kuroshio marches north through the East China Sea, it generates a series of submesoscale eddies along the continental shelf break. Current understandings to these eddies are limited. This work systematically examines the characteristics and mechanism of such eddies using the recently-developed MaCOM model. It is shown that these eddies are mostly generated at the location where the Kuroshio separates from the 200m isobath and deflects northeast (126.5°-127°E，28°-28.5°N). They are only found to the western flank of the Kuroshio and are all cyclonic eddies. They are 2-20 km wide ovals tilting NE-SW, living for 2-20 days, and are mostly active in spring, migrating and carrying mass down the isobath until SW of the Kyushu Island. These eddies are surface-intensified, extending hundreds of meters subsurface. The eddies originate from submesoscale fronts generated by bottom torque west of Kuroshio, developing into ellipse vorticity centers and finally become ellipse valleys of sea level. They acquire energy through barotropic instability, with the energy source located 200-300m deep, but energies are transferred upward and pile up at the surface.  Eddies deposit their kinetic energy to larger-scale flow SW of the Kyushu Island, forming inverse energy cascade there. Eddy activity exhibits significant interannual variability, which, according to preliminary results, is attributable to Kuroshio volume variability and partially to the deflection angle of the Kuroshio relative to the 200m isobath.