Evolution of an anticyclonic eddy southwest of Taiwan

Abstract

Satellite images of sea-surface temperature, surface chlorophyll a concentration, and sea-level anomaly, together with ocean reanalysis data of Asia and Indian-Pacific Ocean (AIPOcean1.0), are utilized to study the three-dimensional characteristics and evolution of an anticyclonic warm eddy adjacent to the southwest coast of Taiwan during October and November 2006. Originated from the Kuroshio intrusion in the Luzon Strait, but unlike previously found westward moving anticyclonic eddies (AE) in the northeastern South China Sea, this AE was so close to the Taiwan coast and stayed where it was formed for over 1 month until it dissipated. Energy analysis is utilized to study the evolution process of the AE, and it shows that the barotropic instability (BTI) and baroclinic instability introduced by the Kuroshio intrusion flow appear to be the main energy sources for the AE. Periodical enhancement/relaxation of local northeasterly monsoon and its associated negative wind stress curl modify the current patterns in this region, reinforce the intraseasonal variability of the Kuroshio intrusion flow, and act together with Kuroshio to form the AE. Eddies detected from AIPOcean1.0 data also show that AEs are most likely to be generated southwest of Taiwan during the transition period of summer monsoon to winter monsoon, and generally, the BTI of Kuroshio intrusion contributes more than the direct wind stress work to the increase of the eddy kinetic energy for the generation and growth of the AEs.

Periodic Mesoscale Eddies in the South China Sea

“…The TAE, on the contrary, dwells locally near the Taiwan coast for about 35 days and therefore shows the shortest propagation distance (Table 1). This result agrees with the case study in 2006 that the TAE had stayed where it was formed for over 1 month and dissipated locally (Zu et al, 2013).…”

“…Trajectories of the LCE and LWE shown in Figures a and z verify this assessment. Although anticyclonic and cyclonic eddies are observed to the southwest of Taiwan in any month of the year (Nan, Xue, et al, ; Zu et al, ), these eddies, neither occurring in fixed time frames nor following similar patterns and trajectories, fail to meet the criteria for periodic eddies.…”

Features of Slope Intrusion Mesoscale Eddies in the Northern South China Sea

“…Mesoscale eddies are active in the NSCS due to wind stress curl (Qu, ; Wang, Chen, et al, ), Kuroshio current loops (Jia et al, ; Zu et al, ), and the intrusion of western Pacific water masses (Hu et al, ; Wu & Chiang, ). Previous studies have investigated the spatiotemporal distribution, properties, motions, and structures of mesoscale eddies in the NSCS (Chen et al, ; He et al, ; Lin, Dong, et al, ; Wang et al, ; Xiu et al, ; Xie et al, ; Zhang et al, ).…”

The topography effect on the sudden deceleration of the mesoscale eddy propagation speed around the Dongsha Islands in northern South China Sea

“…The causes of mesoscale eddies may be revealed to be the bathymetry anomaly (Sangra et al, 2005) or shedding from strong currents such as the Gulf Stream and the Kuroshio (Hurlburt and Thompson, 1980;Li et al, 1998;Hetland et al, 1999;Zu et al, 2013). When the Kuroshio flows over the Luzon Strait, a meander sometimes forms and the mesoscale eddies may be shed from the unstable meander and propagate westward into the SCS (Li et al, 1998;Wang et al, 2000;Yang et al, 2000;Li et al, 2002;Su et al, 2002;Jia and Liu, 2004;Yuan et al, 2006;Zhang et al, 2013).…”

“…Wang et al (2015) pointed out that there are mainly two paths of the mesoscale eddy's westward propagation: one is the along the North South China Sea (NSCS) continental slope, and the other is across the mid-basin from the Philippines moving westward. Along the NSCS continental slope, both the topography and the slope current contribute to the mesoscale eddy propagation (Chow et al, 2008;Wang et al, 2008;Zu et al, 2013). Much of the research has discussed the interaction between the mesoscale eddy and the topography based on ideal numerical experiments (Smith and O'Brien, 1983;Jacob et al, 2002;Sutyrin et al, 2003;Wei and Wang, 2009).…”