A mesoscale eddy pair southwest of Taiwan and its influence on deep circulation

Abstract

[1] A pair of mesoscale eddies, namely, an anticyclonic eddy (AE) and a cyclonic eddy (CE), generated southwest of Taiwan was investigated using long-term moored observations augmented with satellite and reanalysis data. AE (CE) increased the upperocean current to 100 cm/s (50 cm/s) and generated temperature anomaly (T 0 ) up to 7.5 C (23.0 C). The vertical structure of AE presented a phase difference between T 0 and velocity, with the core of T 0 located south of the zero-velocity line. This phase difference induced a 228.5 6 12.0 TW (1 TW 5 10 12 W) westward eddy heat transport southwest of Taiwan. AE also presented strong nonlinearity in the upper ocean and yielded an annual mean volume transport of 0.86 6 0.15 Sv. Energy analysis showed that both baroclinic and barotropic instabilities were important for the generation and growth of the eddy pair, and contribution from wind work was relative small. In the deep sea, AE (CE) intensified the deep currents and generated large positive (negative) T 0 . The deep and surface currents flowed in opposite directions during the eddy events, which is consistent with the interpretation that the eddy pair is dominated by the first baroclinic mode. The observed deep-penetrating eddy pair could greatly influence the deep circulation of the northeastern South China Sea.

A modelling study of eddy-splitting by an island/seamount

“…Eddies have gained much attention since they are an important form of material and energy transfer in the ocean (Zhang et al, 2011(Zhang et al, , 2013(Zhang et al, , 2014Kersalé et al, 2013;Waite et al, 2007;Jacob et al, 2002;Wang et al, 2005). Although isolated eddies in open oceans are affected by different factors, many of them have similar kinematic characteristics in general.…”

“…In particular, mesoscale eddies occur frequently in the northern SCS (Hwang and Chen, 2000;Chang et al, 2012;Zhang et al, 2013;Nan et al, 2011;Wang et al, , 2005, and the number of cold eddies is similar to that of warm eddies. Therefore, it is of importance to find out the difference between the cold and warm eddies.…”

Comparison and validation of global and regional ocean forecasting systems for the South China Sea

“…Some work has analyzed eddies' seasonal variability (Wu and Chiang, 2007;Zhuang et al, 2010) and investigated their origins (D. . Some work has mainly studied specific eddies to better understand eddies' generation, development, and disappearance mechanisms (G. Zhang et al, 2013).…”

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

“…In the SCS, many eddies are observed from in situ observations (Xu et al, 1982;Chu et al, 1998;Li et al, 1998;Hu et al, 2011;Zhang et al, 2013Zhang et al, , 2016 and satellite sea-level anomaly data (Li et al, 2002;Su et al, 2002;Yuan et al, 2007;Chow et al, 2008;Wang et al, 2008). counted the SCS mesoscale eddies using a merged satellite altimeter data set and found that eddies can be mainly grouped into four geographic zones in the SCS.…”

“…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). The mesoscale eddy shedding event can occur all year round (Yuan, 2006).…”