The Role of Fronts in Horizontal Transports of the Changjiang River Plume in Summer and the Implications for Phytoplankton Blooms

Li, Shuangzhao; Zhang, Zhaoru; Zhou, Meng; Wang, Chuning; Wu, Hui; Zhong, Yisen

doi:10.1029/2022jc018541

Cited by 13 publications

(11 citation statements)

References 116 publications

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“…Additionally, the concentrations of nutrients in the surface water of the central gulf during winter (average of 1.64 ± 1.25 μmol L −1 and 0.52 ± 0.11 μmol L −1 for DIN (dissolved inorganic nitrogen, the sum of NH 4 + , NO 3 − and NO 2 − ) and PO 4 3− , respectively) were remarkably higher than that in summer (average of 0.84 ± 0.46 μmol L −1 and 0.26 ± 0.05 μmol L −1 for DIN and PO 4 3− , respectively), suggesting that the nutrient supply is the key factor for phytoplankton blooms in the central gulf. Because of the convergence effect, nutrients carried by different water masses would converge in the frontal region, thus stimulating phytoplankton growth (Chapman et al., 2020; S. Li et al., 2022; Prants, 2022). In the north, strong frontal intensity and high Chl‐ a concentrations were found during winter (Figure 5).…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, periodic offshore blooms (POB) can be induced by the ocean fronts with seasonal characteristics (Guo et al., 2017; Qi et al., 2022). Since offshore waters are less affected by human activities and nutrient‐rich water masses, almost all previous studies about POBs focused on the role of vertical mixing and the upwelling of deeper nutrients by ocean fronts (Guo et al., 2017; S. Li et al., 2022; Taylor & Ferrari, 2011). For example, a POB was reported in the Luzon Strait, which frequently occurred in the northwest of Luzon Island in winter (Peñaflor et al., 2007; Shang et al., 2012; Tang et al., 1999), and the intensity of the POB is positively correlated with the intensity of the ocean front (Guo et al., 2017).…”

Section: Introductionmentioning

confidence: 99%

“…For example, a POB was reported in the Luzon Strait, which frequently occurred in the northwest of Luzon Island in winter (Peñaflor et al., 2007; Shang et al., 2012; Tang et al., 1999), and the intensity of the POB is positively correlated with the intensity of the ocean front (Guo et al., 2017). It is accepted that ocean fronts can enhance the vertical mixing in the water column and upwell deeper eutrophic water to the upper layer, thus stimulating the bloom (Guo et al., 2017; S. Li et al., 2022; Vidya et al., 2021). 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.…”

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%

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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“…The LCSs were utilized to identify the spatial dynamical structures and to investigate the horizontal transport characteristics in the basin‐slope areas at depth. The LCSs can be quantified by the finite‐size lyapunov exponent (FSLE), which has been used to reveal the horizontal transport and track plankton populations moving with currents (d'Ovidio et al., 2015; Lévy et al., 2018; Li et al., 2022). The FSLE is computed from the time interval τ , at which two fluid particles move from an initial separation of δ i to a final separation distance δ f following their trajectories in the two‐dimensional velocity field.…”

Section: Methodsmentioning

confidence: 99%

Dynamical Controls of the Eastward Transport of Overwintering Calanus finmarchicus From the Lofoten Basin to the Continental Slope

et al. 2022

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Diapausing populations of Calanus finmarchicus at depth in the Lofoten Basin (LB) return to the continental shelf and slope off the Lofoten‐Vesterålen Islands during the phytoplankton spring bloom to feed and spawn, forming surface swarms with a great abundance. To study how overwintering populations of C. finmarchicus move with the deep currents and return to the shelf, Lagrangian transport characteristics of particles in deep water between 2008 and 2019 were analyzed using Global Ocean Reanalysis and Simulation re‐analysis data and Lagrangian Coherent Structures (LCSs). Our analyses revealed that persistent eastward transport of diapausing C. finmarchicus between LB and continental slope occurred mainly between 600 and 1,100 m in the Arctic Intermediate Water. The consistency of the vertical distributions of C. finmarchicus abundance and salinity further suggests that physical factors control the horizontal distribution of the species. Hovmöller diagrams of kinetic energy indicate that there is an eastward advection of mean current at depth. The co‐occurrence between the eastward transport of LCSs and the eastward advection of the mean current provides direct evidence that the life history of C. finmarchicus is subjected to physical control in the Norwegian Sea.

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“…In summer, a tremendous amount of river discharge leads to a huge plume region off the CE (Hu et al, 1995;Lie et al, 2003). The river plume significantly regulates the hydrodynamics and nutrient conditions off the CE (Mao et al, 1963;Chang and Isobe, 2003;Zhang et al, 2007;Zhu et al, 2009;Li et al, 2022). Cased by abundant nutrient export, severe eutrophication (Chai et al, 2006;Zhu et al, 2014;Wang et al, 2021b) can form off the CE, and the harmful algal blooms (Li et al, 2014;Yu et al, 2018;Wang et al, 2019b) and subsequent bottom hypoxia (Wang et al, 2016;Wei et al, 2017) are frequently observed during the rainy season.…”

Section: Study Areamentioning

confidence: 99%

Spatial variability of hypoxia and coupled physical-biogeochemical controls off the Changjiang (Yangtze River) Estuary in summer

et al. 2022

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Global estuarine hypoxia is among the most acute environmental issues, yet the recognition of hypoxia variability remains patchy. The Changjiang (Yangtze River) Estuary (CE) is well known as one of the largest estuarine hypoxic systems. However, the mechanisms controlling the spatial variability and heterogeneity of summer hypoxia have been rarely examined in this region. Based on observational data in the summer of 2013, the essential linkages between physical-biogeochemical processes and spatial variability of hypoxia were revealed off the CE. The hypoxia generally occurred in a transitional region off the CE, presenting to be spatially variable and heterogeneous in its distribution and intensity. The river plume, stratification, front, upwelling and localized high phytoplankton biomass combine to shape the spatial morphology and scope of hypoxia. The spatial heterogeneity of hypoxic magnitude in horizontal direction is mainly regulated by the intensity variability of stratification and phytoplankton blooms. The position of bottom front formed by the offshore Taiwan Warm Current (TWC) and coastal water under tidal mixing controls the shoreward boundary of hypoxic zone, while the river plume front-dominated outer edge of phytoplankton blooms in upper layers plays a role in determining the seaward limit of the reach of bottom hypoxia. The stratification depth controlled by the upwelling and river plume governs the upper limit of the top reach of hypoxia, and shapes the vertical morphology of hypoxic zone. We contextualize the role of physical-biogeochemical drivers to the spatially variable hypoxia in a conceptual diagram. The findings would considerably contribute to our understanding of the spatially variable hypoxia in river plume-upwelling-front coupled estuarine systems, providing a sound basis for prediction and simulation under anticipated future conditions.

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The Role of Fronts in Horizontal Transports of the Changjiang River Plume in Summer and the Implications for Phytoplankton Blooms

Cited by 13 publications

References 116 publications

External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

External Dynamic Mechanisms Controlling the Periodic Offshore Blooms in Beibu Gulf

Dynamical Controls of the Eastward Transport of Overwintering Calanus finmarchicus From the Lofoten Basin to the Continental Slope

Spatial variability of hypoxia and coupled physical-biogeochemical controls off the Changjiang (Yangtze River) Estuary in summer

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