Climatic Controls on the Interannual Variability of Shelf Circulation in the Northern South China Sea

Deng, Yongfei; Liu, Zhiqiang; Zu, Tingting; Hu, Jianyu; Gan, Jianping; Lin, Yuxin; Li, Zhibing; Quan, Qi; Cai, Zheng-Li

doi:10.1029/2022jc018419

Cited by 6 publications

(8 citation statements)

References 55 publications

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“…A high‐resolution ocean model showed that the monsoon and the Pearl River greatly influence the WGCC diluted water during summer (Ding et al., 2017), whereas it is driven mainly by monsoons because of the reduction in runoff (Fang et al., 2012; Yang et al., 2002). Stronger (weakened) northeasterly winds because of cyclonic (anticyclonic) anomalies in La Niña (El Niño) years increase (decrease) cold air and water advection from higher latitudes, thus decreasing (increasing) SST in the northern SCS (Deng et al., 2022; Fang et al., 2006). Thus, during La Niña years, the stronger northeast monsoon results in more seawater accumulating along the coast of western Guangdong Province (higher SLA), forming a stronger WGCC that intrudes into the BG (Figure 8).…”

Section: Discussionmentioning

confidence: 99%

“…Thus, existing theories on POBs consider that the intensity of POBs is proportional to the intensity of ocean fronts (nutrient supply of enhanced vertical mixing), ignoring external forcing (climatic oscillations) and external nutrient supply. Because the external forcing, such as El Niño‐Southern Oscillation (ENSO) activities, affects the frontal activities (Hopkins et al., 2010; Wang et al., 2021) and the intensity of transportation of water masses (Deng et al., 2022; Fang et al., 2006). Thus, we speculate that the external forcing can lead to a different mechanism of POBs in the frontal areas.…”

Section: Introductionmentioning

confidence: 99%

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External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

et al. 2023

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Since offshore waters are less affected by human activities and nutrient‐rich water masses, existing theories on periodic offshore blooms (POB) consider that the POB is proportional to the intensity of ocean fronts (nutrient supply from enhancing vertical mixing), ignoring external nutrient supply and external forcing (climatic oscillations). This study proposes an external dynamic mechanism of the POB on the basis of field observations and long‐term satellite remote sensing data (1981–2022) in Beibu Gulf, which is influenced by remarkable external forcing. A strong thermal front with an inverted‐V structure occurred in the central gulf every winter due to the strong wind stress. The intensity of the front on the east side is weaker due to the intrusion of the west‐Guangdong coastal current (WGCC). However, nutrient supply variation resulted in the POB's different intensity in different areas of the inverted‐V front. Chlorophyll a concentrations in the eastern (nutrients supplied by WGCC) and northern (nutrients supplied by vertical mixing) were obviously higher than that in the western front (limited nutrient supply) in winter. On an interannual scale, the intensity of POB in La Niña years is remarkably stronger than in El Niño years due to the stronger WGCC supplying more nutrients in La Niña. This study suggests that the intensity and range of POB are not proportional to the frontal intensity in the gulf, but are directly driven by the internal forcing (fronts and nutrient supply from WGCC), which is controlled by the external forcing.

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

et al. 2023

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“…Monthly averaged riverine discharge data were provided by Chu et al (2022). The subtidal flows and hydrographic properties were extracted from the numerical simulation of the Northern South China Sea, which has been used successfully in the water exchange and interannual variability of shelf circulation (Cai et al, 2022;Deng et al, 2022). To better represent the climatological seasonality of the shelf circulation, we applied the monthly averaged shelf circulation as the subtidal forcing along the southern, western, and eastern open boundaries of the computational domain.…”

Section: Methodology Numerical Modelmentioning

confidence: 99%

Hydrodynamical transport structure and lagrangian connectivity of circulations in the Pearl River Estuary

Chu

Liu

et al. 2022

Front. Mar. Sci.

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Using a three-dimensional (3D) hydrodynamic model, this study explored the seasonal hydrodynamic transport structure in the Pearl River Estuary and illustrated the intrinsic connectivity under multiscale motions from a Lagrangian perspective. Generally, the surface Lagrangian residual current (UL) is uniformly southwestward/southeastward in summer/winter, with a stronger intensity in the lower estuary. The bottom UL features in the southeastward direction in the upper estuary and northwest direction in the lower estuary. The fluvial–tide interaction line advances southeastward and northwestward in summer and winter, respectively. The UL captured the major transport processes and was in good agreement with the mean surface sediment transport patterns. In the transition region between Lantau Island and Neilingding Island, where it is largely affected by the interaction between the periodic tidal current and river discharge, the spatially averaged UL showed intensified intratidal variations and had a larger difference with the locally temporally averaged Eulerian residual current. The remarkable Lagrangian coherent structures that illustrated the transport paths and transport convergence regions were identified, which are generally consistent with the bottom sediment depocenters. Based on the Lagrangian connectivity analysis, it was revealed that a barrier between the western and eastern estuaries existed, which was weakened by the strong river discharge during summer. Two convergence regions near the Macau and Hong Kong waters were identified, where the sediment and pollutants easily settled. The study demonstrated the importance of the Lagrangian view in understanding the hydrodynamic process and transport structure in the estuary–shelf regions.

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“…It is also noted that hydrodynamic processes in NSCS exhibit significant interannual variability under the modulation of climatic changes. Affected by the El Niño-Southern Oscillation (ENSO), a stronger northeastward/southwestward flow anomaly occurs in the El Niño/La Niña years, and the asymmetric response to the ENSO was noticed that a larger anomaly intensity tends to occur in El Niño years (Deng et al, 2022;N. Liu et al, 2020).…”

Section: Introductionmentioning

confidence: 99%

“…It is also noted that hydrodynamic processes in NSCS exhibit significant interannual variability under the modulation of climatic changes. Affected by the El Niño–Southern Oscillation (ENSO), a stronger northeastward/southwestward flow anomaly occurs in the El Niño/La Niña years, and the asymmetric response to the ENSO was noticed that a larger anomaly intensity tends to occur in El Niño years (Deng et al., 2022; N. Liu et al., 2020). Driven by the complicated motions, the water exchange structure in the NSCS and its response to the climatic variabilities is crucial for comprehending the regional biogeochemical processes but remains largely unclear.…”

Section: Introductionmentioning

confidence: 99%

Three‐Dimensional Water Exchanges in the Shelf Circulation System of the Northern South China Sea Under Climatic Modulation From ENSO

Cui,

Liu,

Chen

et al. 2024

JGR Oceans

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Using the numerical calculations of exposure time (), this study investigated the three‐dimensional characteristics of water exchanges associated with the coastal‐shelf circulations of the Northern South China Sea (NSCS). The circulation connectivity and its interannual variability under the modulation of El Niño Southern Oscillation (ENSO) were investigated. The gradually increased from approximately 50 days over the outer shelf to more than 150 days in the shallower coastal seas with the Beibu Gulf displaying a significantly longer (approximately 300 days). The Beibu Gulf played an influential role in the water exchange that had a contribution of over 30% to in the most regions. The results from sensitivity experiments indicate that the wind forcing is the primary controller of and the boundary flux plays a secondary role. Specifically, the wind enhances water exchange in western NSCS, particularly in the Beibu Gulf and Yuexi region. Conversely, boundary fluxes facilitate exchanges in the eastern shelf, such as Yuedong region. Analysis revealed a clear modulation from ENSO on water exchange, wherein El Niño and La Niña years displayed symmetrical morphologies in distribution anomalies, albeit with varying intensities. During El Niño years, the weakened southwestward shelf current increased and the shelf water was less likely to reach the Beibu Gulf, and once arrived, these waters were trapped inside to elongate . In contrast, during La Niña years, the strengthened southwestward shelf current shortened and more shelf waters were transported away from the NSCS by an intensified southwestward shelf current.

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Climatic Controls on the Interannual Variability of Shelf Circulation in the Northern South China Sea

Cited by 6 publications

References 55 publications

External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

Hydrodynamical transport structure and lagrangian connectivity of circulations in the Pearl River Estuary

Three‐Dimensional Water Exchanges in the Shelf Circulation System of the Northern South China Sea Under Climatic Modulation From ENSO

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