scholarly journals Intensification of Downslope Nutrient Transport and Associated Biological Responses Over the Northeastern South China Sea During Wind-Driven Downwelling: A Modeling Study

2021 ◽  
Vol 8 ◽  
Author(s):  
Aiqin Han ◽  
Jianping Gan ◽  
Minhan Dai ◽  
Zhongming Lu ◽  
Linlin Liang ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
Coastal Upwelling ◽  
Nutrient Transport ◽  
Field Measurements ◽  
Time Lags ◽  
Biological Productivity ◽  
China Sea ◽  
Northeastern South China Sea

Coastal downwelling is generally considered to have a limited biological effect compared with coastal upwelling. In this study, downslope transport of nearshore, nutrient-enriched waters during downwelling is found to induce distinct biological productivity in the water column over the northeastern South China Sea (NSCS). By conducting a process-driven study over a widened shelf with intensified downwelling in the NSCS, we investigated the biophysical processes associated with strong nutrient enrichment in the water column of downwelled waters. These processes and underlying mechanisms are largely unreported and remain unclear. Field measurements and a three-dimensional coupled physical-biological model incorporating nitrate (N), phytoplankton (P), zooplankton (Z), and detritus (D) were utilized to investigate distinct cross-shore nutrient transport over the uniquely widened NSCS shelf. We revealed that intensified downwelling circulation, dynamically induced by the widened shelf topography, enhanced chlorophyll a and biological productivity in a strip of well-mixed water over the inner shelf as well as in the downwelled water over the mid-shelf. Strong time lags and spatial differences existed among N, P, and Z because of the physical transport and the ensuing biogeochemical response. The intensified downslope transport of nutrient-rich coastal water formed distinct cross-shore wedge-shaped P, Z, and D structures, while N was rapidly consumed in the water column. This study illustrates the underlying coupled physical-biogeochemical processes associated with the observed biogeochemical response to wind-driven downwelling circulation over the variable shelf, which are commonly found in coastal oceans worldwide.

Interaction of a river plume with coastal upwelling in the northeastern South China Sea

2009 ◽  
Vol 29 (4) ◽  
pp. 728-740 ◽  
Author(s):  
Jianping Gan ◽  
Li Li ◽  
Dongxiao Wang ◽  
Xiaogang Guo
Keyword(s):  
South China Sea ◽  
South China ◽  
Coastal Upwelling ◽  
River Plume ◽  
China Sea ◽  
Northeastern South China Sea

scholarly journals Phytoplankton dynamics driven by vertical nutrient fluxes during the spring inter-monsoon period in the northeastern South China Sea

2015 ◽  
Vol 12 (9) ◽  
pp. 6723-6755 ◽  
Author(s):  
Q. P. Li ◽  
Y. Dong ◽  
Y. Wang
Keyword(s):  
South China Sea ◽  
South China ◽  
Turbulent Diffusion ◽  
Coastal Upwelling ◽  
Phytoplankton Bloom ◽  
Nutrient Fluxes ◽  
Monsoon Period ◽  
China Sea ◽  
Northeastern South China Sea

Abstract. A field survey from the coastal upwelling zones to the offshore pelagic zones of the northeastern South China Sea (SCS) was conducted during the inter-monsoon period of May 2014 when the region was characterized by prevailing low-nutrient conditions. Comprehensive field measurements were made for not only hydrographic and biogeochemical properties but also phytoplankton growth and microzooplankton grazing rates. We also performed estimations of the vertical turbulent diffusivity and diffusive nutrient fluxes using a Thorpe-scale method and the upwelling nutrient fluxes by Ekman pumping using satellite-derived wind stress curl. Our results suggest that phytoplankton patchiness in the northeastern SCS during the study period could be largely controlled by vertical nutrient fluxes with combined contributions from both turbulent diffusion and curl-driven upwelling. Our results also reveal the generally increasing role of turbulent diffusion but decreasing role of curl-driven upwelling on vertical transport of nutrients from the coastal upwelling zones to the offshore pelagic zones in the northeastern SCS. Elevated nutrient fluxes observed near Dongsha Island were found to support high new production leading to net growth of a diatom-rich phytoplankton community, whereas the low nutrient fluxes near southwest Taiwan resulted in a negative net community growth leading to a decline of a picoplankton-dominant phytoplankton bloom.

scholarly journals Coastal upwelling in summer 2000 in the northeastern South China Sea

2012 ◽  
Vol 117 (C4) ◽  
pp. n/a-n/a ◽  
Author(s):  
Dongxiao Wang ◽  
Wei Zhuang ◽  
Shang-Ping Xie ◽  
Jianyu Hu ◽  
Yeqiang Shu ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Coastal Upwelling ◽  
China Sea ◽  
Northeastern South China Sea

scholarly journals Marine Group II Dominates Planktonic Archaea in Water Column of the Northeastern South China Sea

2017 ◽  
Vol 8 ◽  
Author(s):  
Haodong Liu ◽  
Chuanlun L. Zhang ◽  
Chunyan Yang ◽  
Songze Chen ◽  
Zhiwei Cao ◽  
...  
Keyword(s):  
South China Sea ◽  
Water Column ◽  
South China ◽  
China Sea ◽  
Group Ii ◽  
Northeastern South China Sea

scholarly journals Physical modulation to the biological productivity in the summer Vietnam upwelling system

Ocean Science ◽  
2018 ◽  
Vol 14 (5) ◽  
pp. 1303-1320 ◽  
Author(s):  
Wenfang Lu ◽  
Lie-Yauw Oey ◽  
Enhui Liao ◽  
Wei Zhuang ◽  
Xiao-Hai Yan ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
South China Sea ◽  
Ocean Circulation ◽  
South China ◽  
Coastal Upwelling ◽  
Coupled Model ◽  
Biological Productivity ◽  
High Productivity ◽  
China Sea ◽  
Upwelling System

Abstract. Biological productivity in the summer Vietnam boundary upwelling system in the western South China Sea, as in many coastal upwelling systems, is strongly modulated by wind. However, the role of ocean circulation and mesoscale eddies has not been elucidated. Here, we show a close spatiotemporal covariability between primary production and kinetic energy. High productivity is associated with high kinetic energy, which accounts for ∼15 % of the production variability. Results from a physical–biological coupled model reveal that the elevated kinetic energy is linked to the strength of the current separation from the coast. In the low production scenario, the circulation is not only weaker but also shows weak separation. In the higher production case, the separated current forms an eastward jet into the interior South China Sea, and the associated southern recirculation traps nutrients and favors productivity. When separation is absent, the model shows weakened circulation and eddy activity, with ∼21 % less nitrate inventory and ∼16 % weaker primary productivity.

scholarly journals Physical Modulation to the Biological Productivity in the Summer Vietnam Upwelling System

2018 ◽  
Author(s):  
Wenfang Lu ◽  
Enhui Liao ◽  
Xiao-Hai Yan ◽  
Lie-Yauw Oey ◽  
Wei Zhuang ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
South China Sea ◽  
Ocean Circulation ◽  
South China ◽  
Coastal Upwelling ◽  
Current System ◽  
Coupled Model ◽  
Biological Productivity ◽  
China Sea ◽  
Upwelling System

Abstract. Biological productivity in the summer Vietnam boundary upwelling system in the western South China Sea, as in many coastal upwelling systems, is strongly modulated by wind. However, the role of ocean circulation and mesoscale eddies has not been elucidated. Here we show a close spatio-temporal covariability between primary production and kinetic energy. High productivity is associated with high kinetic energy, which accounts for ~ 15 % of the production variability. Results from a physical-biological coupled model reveal that the elevated kinetic energy and intensified circulation can be explained by the separation of the upwelling current system. The separated current forms an eastward jet into the interior South China Sea, and the associated southern gyre traps nutrient and favors productivity. When separation is absent, the model shows weakened circulation and eddy activity, with ~ 21 % less nitrate inventory and ~ 16 % weaker primary productivity.

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