Antisymmetry of oceanic eddies across the Kuroshio over a shelfbreak

Yu Liu,Jihai Dong,Xiaohui Liu,Changming Dong

doi:10.1038/s41598-017-07059-1

Abstract

From the analysis of oceanic eddies detected in the drifter trajectories of the Global Drifter Program (GDP) data set, it was found that oceanic eddies are asymmetrically distributed across the Kuroshio in the East China Sea: predominant cyclonic (anticyclonic) eddies are on the western (eastern) sides of Kuroshio. This distribution is confirmed by high-resolution numerical modeling output as well. Most of these eddies are 5~20 km in radius, less than the local first baroclinic deformation radius, thus categorized as submesoscale. The generation mechanism of these submesoscale eddies is speculated to be related to the horizontal velocity shear of the Kuroshio when it flows northeastward along the shelf break in the East China Sea. The budget analysis of eddy kinetic energy shows that both the horizontal shear and vertical buoyancy flux are important energy sources for eddy generation on the two sides of Kuroshio axis. The finding highlights the unique feature of oceanic eddies along the western boundary currents.

Highlights

The Kuroshio is a well-known energetic western boundary current in the northwest Pacific Ocean
Because the mean horizontal shear is an important dynamic mechanism of eddy generation, we speculate that the MPK should produce mesoscale or sub-mesoscale eddies along its two sides and with eddy size constrained by the width of MPK
The climatological Kuroshio with speed larger than 50 cm s−1 is shown in bold black arrows in the area east to the mainland of China and west to the Ryukyu Islands (Fig. 1). It is derived from 2000–2013 Global Drifter Program (GDP) drifter trajectory data

Summary

OPEN Antisymmetry of oceanic eddies across the Kuroshio over a shelfbreak

From the analysis of oceanic eddies detected in the drifter trajectories of the Global Drifter Program (GDP) data set, it was found that oceanic eddies are asymmetrically distributed across the Kuroshio in the East China Sea: predominant cyclonic (anticyclonic) eddies are on the western (eastern) sides of Kuroshio This distribution is confirmed by high-resolution numerical modeling output as well. The Kuroshio is a well-known energetic western boundary current in the northwest Pacific Ocean (see Fig. 1) From both observational analysis[1] and statistical detection results from various satellite data sets[2, 3], abundant eddies occur along the Kuroshio path. These eddies are not visualized in the low-resolution satellite images[2, 3], so the drifter data and high-resolution model output are employed to detect these eddies

Results

Methods

Additional Information