Comment on “Current separation and upwelling over the southeast shelf of Vietnam in the South China Sea” by Chen et al.

Dippner, Joachim W.; Bombar, Deniz; Loick‐Wilde, Natalie; Voß, Maren; Subramaniam, Ajit

doi:10.1002/jgrc.20118

Cited by 18 publications

(16 citation statements)

References 27 publications

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“…This statistical analysis of the strong interannual variability of the SVU, integrated over the upwelling season, confirms the key role of atmospheric forcing in inducing variations in spatial distributions and total strength, as proposed previously (e.g., Dippner et al, ; Li et al, ). The significant correlations between CTRL, SimO, and SimR, together with the nonsignificant correlations between CTRL, SimA, and SimI, confirm that the interannual chronology of the SVU is mainly driven by the atmospheric forcing.…”

Section: Interannual Variability Of Svu and Contribution Of Differentsupporting

confidence: 89%

“…Two different mechanisms have been proposed to explain how ENSO impacts the SVU. The first one implies a direct effect through local summer wind modulation, suggesting that ENSO modulates the summer southwest monsoon and thus impacts the wind‐induced SVU (Dippner et al, ; Lau & Yang, ; Xie et al, ). The second hypothesis is an indirect effect via changes in the large‐scale circulation and thermohaline structure (Hein et al, ; Li et al, ; Qu et al, ).…”

Section: Introductionmentioning

confidence: 99%

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Contributions of Wind, Ocean Intrinsic Variability, and ENSO to the Interannual Variability of the South Vietnam Upwelling: A Modeling Study

Herrmann

Morrow

et al. 2019

JGR Oceans

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The summer South Vietnam Upwelling (SVU) is a major component of the South China Sea circulation where it also influences ecosystems. Here we revisit the existing knowledge of the SVU interannual variability. Based on a set of 15-year eddy-resolving sensitivity simulations, we quantify the respective contributions from different factors (atmospheric, river, and oceanic forcings; ocean intrinsic variability; and El Niño Southern Oscillation) to this interannual variability and explore the underlying mechanisms. Our sea surface temperature upwelling indices allow us to quantify the strong SVU interannual variability in terms of strength and spatial distribution. Strong SVU years are offshore dominant with SVU centers located within 11-12°N and 110-112°E, whereas weak SVU years are coastal dominant with SVU centers located near the coast and spanning a larger 10-14°N latitude range. Our study confirms the leading influence of the summer wind and further reveals that coastal SVU variability is related to the variability of the eastward jet that develops from the coast, whereas offshore SVU variability is strongly driven by the spatiotemporal collocation of wind stress curl with cyclonic eddies. Ocean intrinsic variability, and to a lesser extent perturbations induced by river discharge and lateral oceanic conditions, strongly triggers interannual variability of background eddy circulation, thus of the SVU. El Niño Southern Oscillation influences the SVU mainly through its direct influence on summer winds. Plain Language SummaryThe coastal seas along Southern Vietnam are rich in nutrients during the summer, and fish find an abundant supply of food in the region. The summer wind blows the surface waters offshore and pumps up deep, cold, nutrient-rich water in this "upwelling" region, allowing plankton to thrive at the surface where sunlight is available. Three factors strengthen the upwelling strength: stronger wind speed, wind blowing counterclockwise, and the presence of counterclockwise rotating eddies, which all contribute to pump up deep, nutrient-rich waters to the surface. Based on numerical modeling studies of ocean circulation, we found that when those three factors occur simultaneously, they pump up much more deep water than each of them alone. On the other hand, wind blowing clockwise or clockwise rotating eddies tend to pump water downward. While it is possible to predict upwelling produced by the wind, the ocean eddies whose radius ranges from tens to hundreds of kilometers move more randomly, and it is difficult to predict their contribution to the upwelling strength. We also found that El Niño weakens the wind and favors clockwise eddy circulation in the upwelling area. Thus, in strong El Niño years, upwelling is weaker in the seas off Southern Vietnam.

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Section: Interannual Variability Of Svu and Contribution Of Differentsupporting

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Contributions of Wind, Ocean Intrinsic Variability, and ENSO to the Interannual Variability of the South Vietnam Upwelling: A Modeling Study

Herrmann

Morrow

et al. 2019

JGR Oceans

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“…Despite the above findings, our knowledge about the dynamics of the SEJ is far from complete. While large year-to-year variations in SCS sea level, SST, and upper ocean circulation have been reported and shown to be highly correlated with the El Niño-Southern Oscillation (ENSO) indices [e.g., Chao et al, 1996; Xie et al, [Reynolds et al, 2007], the Ocean Surface Current Analyzes-Real time (OSCAR) product [Bonjean and Lagerloef, 2002], and the Archiving, Validation, and Interpretation of Satellite Oceanographic data (AVISO) sea level data [Le Traon et al, 1998;Ducet et al, 2000]. 2003; Qu et al, 2004;Fang et al, 2006;Rong et al, 2007;Chang et al, 2008;Liu et al, 2011;Dippner et al, 2013], interannual variability of the SEJ has never been systematically examined. Proceeding of relevant research is hampered by the ability of existing ocean general circulation models (OGCMs) to simulate the key processes associated with the SEJ variability.…”

Section: Introductionmentioning

confidence: 99%

Interannual variability of the surface summertime eastward jet in the South China Sea

Han

Wilkin

et al. 2014

JGR Oceans

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Remote wind forcing from the tropical Pacific can also affect the sea level in the SCS via energy transmission through the Philippine archipelago, but its effect on the SEJ is small. The impact of the oceanic internal variability, such as eddy-current interaction, is assessed using an ocean general circulation model (OGCM). Such impact can lead to considerable year-to-year changes of sea level and the SEJ, equivalent to 20% of the observed variation. This implies the complexity and prediction difficulty of the upper ocean circulation in this region.

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“…From November to March, northeast winds prevail [ Dippner et al ., ; Xie et al ., ], originating in China and northern Vietnam, whereas from June to September, southwest winds prevail originating in Southeast Asian countries and southern Vietnam (Figure b). During the Southwest Monsoon, upwelling occurs at ~12°N off the central Vietnamese coast [ Xie et al ., ], bringing deeper water [ Dippner et al ., ] with possibly older Pb to the site.…”

Section: Sampling and Analysismentioning

confidence: 99%

Lead in the western South China Sea: Evidence of atmospheric deposition and upwelling

Chen

Goodkin

Boyle

et al. 2016

Geophysical Research Letters

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In recent decades, rapid industrial developments have increased lead (Pb) inputs to the South China Sea. To quantify the increasing variability, we investigated 170 years of skeletal Pb and Pb isotopes from an offshore, central Vietnamese coral. The Pb/Ca in the coral was 10–16 nmol/mol before the mid‐1950s and increased to more than 30 nmol/mol by 2000. While the regional phaseout of leaded petrol commenced in 2000, coral Pb/Ca continued increasing until 2004, possibly due to regional upwelling and the transport of previously emitted Pb from tropical Pacific waters. The 206Pb/207Pb ratio in the coral was 1.191–1.195 before mid‐1950s, suggesting natural sources. Since then, the ratio decreased, reaching ~1.165 in 2004. Lead isotopes show high linearity between natural and Chinese emitted Pb, with the latter contributing ~40%~60% of the skeletal Pb after 2000.

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Comment on “Current separation and upwelling over the southeast shelf of Vietnam in the South China Sea” by Chen et al.

Cited by 18 publications

References 27 publications

Contributions of Wind, Ocean Intrinsic Variability, and ENSO to the Interannual Variability of the South Vietnam Upwelling: A Modeling Study

Contributions of Wind, Ocean Intrinsic Variability, and ENSO to the Interannual Variability of the South Vietnam Upwelling: A Modeling Study

Interannual variability of the surface summertime eastward jet in the South China Sea

Lead in the western South China Sea: Evidence of atmospheric deposition and upwelling

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