Oceanic eddy formation and propagation southwest of Taiwan

Nan, Feng; Xue, Huijie; Xiu, Peng; Chai, Fei; Shi, Maochong; Peifang, Guo

doi:10.1029/2011jc007386

Cited by 107 publications

(89 citation statements)

References 43 publications

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“…In 2005, the AE was extremely strong, and simultaneously, T4 and WW were also larger than other times. Similar as that pointed out by Nan et al (2011c), Kuroshio instability is more important than direct wind effects on the AE formation southwest of Taiwan. However, periodical variation of the wind reinforce the Kuroshio variability, and the wind stress work on the mean flow could also be transferred to the EKE through BTI.…”

Section: Barotropic Instability and Direct Wind Stress Worksupporting

confidence: 80%

“…5). The correlation of the eddy generation (indicated by eddy-occupied areas) southwest of Taiwan with the Kuroshio path variability (indicated by geostrophic vorticity) and local wind forcing (indicated by the wind stress curl) suggested that Kuroshio was a more important factor for eddy generations (Nan et al 2011c). But their relative importance during the development of an eddy had not been quantitatively discussed yet.…”

Section: Energy Analysismentioning

confidence: 99%

“…Wu et al (2005) also showed intraseasonal variation of the circulation structure as it sometimes could be cyclonic, and they suggested it was likely triggered by the variation of strong wind stress curl. By correlation analysis of altimetry data, Nan et al (2011c) found that the Kuroshio path variation was dominant for eddy generation southwest of Taiwan compared with local wind forcing. However, the relative importance of the two forcing mechanisms has never been quantitatively evaluated during the development of an eddy.…”

Section: Introductionmentioning

confidence: 99%

“…Mechanisms of eddy formation in the NSCS could be summarized into three types according to the previous studies. The first type is eddy shedding from the Kuroshio loop current (Li et al 1998;Metzger and Hurlburt 2001;Jia and Liu 2004;Jia et al 2005;Yuan et al 2006;Wu and Chiang 2007;Wang et al 2008a;Chen et al 2011a;Nan et al 2011c), which is caused by the frontal instability of the Kuroshio branch that intrudes into the northeastern SCS (NESCS). The second type is eddy generated locally by wind stress curl Wang et al 2008b); the orographic wind jet and enhanced wind stress curl in the lee of the Taiwan Island and Luzon Island chains could lead to stronger Ekman pumping and spin up eddies.…”

Section: Introductionmentioning

confidence: 99%

“…The generation of an AE during winter is mainly attributed to the shedding from the Kuroshio loop current when its transport is weakened, and their formation is usually associated with the cyclonic eddy development next to it (Jia et al 2005;Nan et al 2011c). During summer, AEs are mainly generated around the northwest of Luzon, in phase with the onset of the southwesterly monsoon and the relaxation of the wind stress curl ).…”

Section: Introductionmentioning

confidence: 99%

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Evolution of an anticyclonic eddy southwest of Taiwan

Wang

et al. 2013

Ocean Dynamics

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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.

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Section: Barotropic Instability and Direct Wind Stress Worksupporting

confidence: 80%

Section: Energy Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Evolution of an anticyclonic eddy southwest of Taiwan

Wang

et al. 2013

Ocean Dynamics

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

et al. 2013

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[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.

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Ocean salinity changes in the northwest Pacific subtropical gyre: The quasi‐decadal oscillation and the freshening trend

Nan

Xue

et al. 2015

JGR Oceans

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Ocean salinity changes play an important role in modulating ocean and climate variability.Analyses of the repeating observations along PN, TK, and 137 E sections reveal that both surface and subsurface salinity in the Northwest Pacific Subtropical Gyre (NPSG) had clear quasi-decadal oscillation (QDO) of $10 year and a sustained freshening trend during 1987-2012. Surface salinity in the NPSG troughed in 1989, 1999, and 2008, and peaked in 1993, and 2003. The peak-to-tough range of surface salinity oscillation can reach 0.3 psu. Meanwhile, surface salinity decreased about 0.10 psu from 1987 to 2012 with a freshening trend of 20.0042 psu yr 21 . These surface salinity anomalies were subducted into the subsurface layer mainly in the ventilated zone along the Kuroshio Extension, and advected over the NPSG. The QDO of the subsurface salinity maximum (S max ) lagged that of the surface salinity by about 1$2 years. Both the peakto-tough range of the S max oscillation (0.15 psu) and its freshening trend (20.0036 psu yr 21) are smaller than those of the surface salinity. Salinity changes in the NPSG likely began in the mid-1970s associated with the North Pacific regime shift during 1976/1977. Analyses of mixed layer salinity budget indicated that air-sea freshwater flux change in the NPSG is the leading factor controlling the surface salinity anomalies, while change of large-scale ocean circulation (Geostrophic advection) also plays a minor role. Salinity and air-sea freshwater flux changes in the NPSG are all closely related to the Pacific Decadal Oscillation, indicating the large-scale ocean-atmosphere interaction.

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Oceanic eddy formation and propagation southwest of Taiwan

Cited by 107 publications

References 43 publications

Evolution of an anticyclonic eddy southwest of Taiwan

Evolution of an anticyclonic eddy southwest of Taiwan

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

Ocean salinity changes in the northwest Pacific subtropical gyre: The quasi‐decadal oscillation and the freshening trend

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