Prof. Dong-Kyu Lee

Department of Oceanography

Pusan National University, Busan, Korea

Email: dglee@pnu.edu

Research Interests: Mesoscale eddies. Air-sea interaction in eddies. El Niño.

The formation of core convergent eddy by wrapping low density water around the warm eddy.

Abstract

The wrapping low-density water (LDW) generates a geostrophic flow opposite to the clockwise direction of the warm eddy and effectively decelerates it. The geostrophic flow weakens along the periphery of the eddy as the LDW gradually mixes horizontally with surrounding water, resulting in an accelerated current around the warm eddy. When the mixing rate of the entrained LDW on outer side of the eddy is more than that on inner side of eddy, the LDW moves toward the center of the eddy like a spiral due to the flow accelerated more on outer side than on inner side of LDW. Based on observations and reanalysis data from the numerical model, it is shown that the accelerated surface flow induces upwelling along the LDW. Upwelling along the periphery of the eddy makes the core convergent eddy, resulting in the long-lasting, surface-trapped and isolated eddy. In April in the southwestern Japan Sea, the warm current from the south merges with the anticyclone and encircles the clockwise-rotating anticyclone. A high Chl-a concentration area in the form of a ring forms around the eddy along the accelerated surface flow. The trapped drifters for more than three months were observed in the eddies of the Japan Sea formed by such a wrapping LDW.