Late Holocene (~ 2 ka) East Asian Monsoon variations inferred from river discharge and climate interrelationships in the Pearl River Estuary

2014 ◽  
Vol 81 (2) ◽  
pp. 240-250 ◽  
Author(s):  
Qingyun Nan ◽  
Tiegang Li ◽  
Jinxia Chen ◽  
Rajiv Nigma ◽  
Xinke Yu ◽  
...  
Keyword(s):  
Grain Size ◽  
River Discharge ◽  
Late Holocene ◽  
Monsoon Rainfall ◽  
East Asian ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

AbstractA sediment core from the Pearl River Estuary (PRE) was analyzed for grain size and organic geochemistry parameters (TOC and δ13Corg). The results showed that high mean grain-size value and increased sand content were correlated with the high TOC and negative δ13Corg. These results indicated high river runoff in the PRE area. Peak river discharge occurred during the periods 1900–1750, 1500–1600, 1400–1200, 1000–900 and 750–600 cal yr BP. The main changes recorded in grain-size distributions, TOC contents, and δ13Corg variations appear to be directly related to monsoon precipitation in the sediment source area. An increased East Asian summer monsoon rainfall (EASM) and/or an enhanced East Asian winter monsoon rainfall could result in the increasing of monsoon rainfall. Typhoon related rainfalls could act as positive influence on precipitation levels. The study of the correlations between the rainfall records and ENSO activities revealed a close relationship between the monsoon rainfall in the PRE and the tropical Pacific variations. The frequent occurrence of ENSO might result in the southern migration of the EASM rain belt and lead to more typhoon-derived rainfall in the PRD during the late Holocene.

scholarly journals Mid-Holocene variability of the East Asian monsoon based on bulk organic δ13C and C/N records from the Pearl River estuary, southern China

The Holocene ◽  
2011 ◽  
Vol 22 (6) ◽  
pp. 705-715 ◽  
Author(s):  
Fengling Yu ◽  
Yongqiang Zong ◽  
Jeremy M Lloyd ◽  
Melanie J Leng ◽  
Adam D Switzer ◽  
...  
Keyword(s):  
Asian Monsoon ◽  
East Asian Monsoon ◽  
Southern China ◽  
East Asian ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

scholarly journals Implications of Nutrient Enrichment and Related Environmental Impacts in the Pearl River Estuary, China: Characterizing the Seasonal Influence of Riverine Input

Water ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 3245
Author(s):  
Lixia Niu ◽  
Pieter van Gelder ◽  
Xiangxin Luo ◽  
Huayang Cai ◽  
Tao Zhang ◽  
...  
Keyword(s):  
Nutrient Enrichment ◽  
River Discharge ◽  
Nutrient Dynamics ◽  
Southern China ◽  
Salinity Gradient ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
The Pearl River

The Pearl River estuary is an ecologically dynamic region located in southern China that experiences strong gradients in its biogeochemical properties. This study examined the seasonality of nutrient dynamics, identified related environmental responses, and evaluated how river discharge regulated nutrient sink and source. The field investigation showed significant differences of dissolved nutrients with seasons and three zones of the estuary regarding the estuarine characteristics. Spatially, nutrients exhibited a clear decreasing trend along the salinity gradient; temporally, their levels were obviously higher in summer than other seasons. The aquatic environment was overall eutrophic, as a result of increased fluxes of nitrogen and silicate. This estuary was thus highly sensitive to nutrient enrichment and related pollution of eutrophication. River discharge, oceanic current, and atmospheric deposition distinctly influenced the nutrient status. These factors accordingly may influence phytoplankton that are of importance in coastal ecosystems. Phytoplankton (in terms of chlorophyll) was potentially phosphate limited, which then more frequently resulted in nutrient pollution and blooms. Additionally, the nutrient sources were implied according to the cause–effect chains between nutrients, hydrology, and chlorophyll, identified by the PCA-generated quantification. Nitrogen was constrained by marine-riverine waters and their mutual increase-decline trend, and a new source was supplemented along the transport from river to sea, while a different source of terrestrial emission from coastal cities contributed to phosphate greatly.

scholarly journals Effects of Physical Forcing on Summertime Hypoxia and Oxygen Dynamics in the Pearl River Estuary

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2080 ◽  
Author(s):  
Huang ◽  
Hu ◽  
Li ◽  
Wang ◽  
Xu ◽  
...  
Keyword(s):  
River Discharge ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Vertical Diffusion ◽  
Physical Forcing ◽  
The Pearl River Estuary ◽  
Hypoxic Area ◽  
Water Stratification ◽  
The Pearl River

A validated hydrodynamic-biogeochemical model was applied to investigate the effects of physical forcing (i.e., river discharge, winds, and tides) on the summertime dissolved oxygen (DO) dynamics and hypoxia (DO < 3 mg L−1) in the Pearl River estuary (PRE), based on a suite of model sensitivity experiments. Compared with the base model run in 2006 (a wet year), the simulated hypoxic area in the moderate year (with 75% of river discharge of the base run) and the dry year scenario (with 50% of river discharge of the base run) was reduced by ~30% and ~60%, respectively. This is because under the lower river discharge levels, less particulate organic matter was delivered to the estuary that subsequently alleviated the oxygen demand at the water–sediment interface, and in the meantime, the water stratification strength was decreased, which facilitated the vertical diffusion of DO. Regarding the effect of winds, the highly varying and intermittent strong winds had a significant impact on the replenishment of bottom DO by disrupting water stratification and thus inhibiting the development of hypoxia. Sensitivity experiments showed that the hypoxic area and volume were both remarkably increased in the low wind scenario (with a bottom hypoxic zone extending from the Modaomen sub-estuary to the western shoal in Lingdingyang Bay), whereas hypoxia was almost absent in the strong wind scenario. The DO budget indicated that winds altered the bottom DO mostly by affecting the DO flux due to vertical diffusion and horizontal advection, and had a limited influence on the DO consumption processes. Moreover, the DO concentration exhibited remarkable fluctuations over the spring-neap tidal cycles due to the significant differences in vertical diffusion. The results of a tide-sensitivity experiment indicated that without tide forcing, most of the shallow areas (average water depth < 5 m) in the PRE experienced severe and persistent hypoxia. The tides mainly enhanced mixing in the shallow areas, which led to higher vertical diffusion and enhanced replenishment of bottom DO.

Early and late Holocene paleoenvironmental reconstruction of the Pearl River estuary, South China Sea

2020 ◽  
Author(s):  
Huixian Chen ◽  
Jianhua Wang ◽  
Nicole S. Khan ◽  
Jiaxue Wu ◽  
Benjamin P. Horton
Keyword(s):  
Sea Level ◽  
Late Holocene ◽  
Asian Monsoon ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
Sea Level Changes ◽  
The Pearl River Estuary ◽  
The Pearl River ◽  
Middle Estuary

&lt;p&gt;Proxy reconstructions of estuarine evolution provide perspectives on regional to global environmental changes, including relative sea-level changes, climatic changes, and agricultural developments. Although there are studies of the Holocene sedimentary processes in the Pearl River estuary, the understanding of early Holocene sedimentation in unknown due to limited preservation.&lt;/p&gt;&lt;p&gt;Here, we present a new record of lithological, benthic foraminiferal, and geochemical (&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and C/N) change from a sediment core in the west shoal of the modern Lingding Bay along a paleo-valley. The lithologic and foraminiferal record reveal the transgressive evolution from fluvial, inner estuary to middle estuary in the early Holocene between 11300 and 8100 cal a BP in response to rapid sea-level rise. &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and C/N data indicate high freshwater discharge from 10500 to 8100 cal a BP driven by a strong Asian monsoon. The middle Holocene (8100 - 3300 cal a BP) sediment is absent in this core and others in the northward of the Lingding Bay. Seismic profiles reveal a tidal ravinement surface across Lingding Bay, which contributed to subaqueous erosion on the mid-Holocene sedimentation hiatus, might be resulted from unique geomorphology of the Pearl River Delta. In the late Holocene (3300 cal a BP to the present), the lithology and foraminiferal assemblages suggest further regressive evolution from outer estuary, middle estuary channel, to middle estuary shoal due to deltaic progradation under stable relative sea levels. In the last 2000 years, &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C and C/N values reveal the intensive development of agriculture coupled with the reduction of freshwater input derived from a weakening Asian monsoon. Our study illustrates the interaction of Asian monsoon and sea-level changes within the Pearl River estuary landform and their impact on Holocene sedimentary processes.&lt;/p&gt;

Distribution Characteristics and Environmental Impacts of Nutrients in the Dry Season of the Pearl River Estuary in 2016

2020 ◽  
Author(s):  
Danna Zeng ◽  
Lixia Niu ◽  
Qingshu Yang
Keyword(s):  
Chlorophyll A ◽  
River Discharge ◽  
Spring Tide ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Dry Season ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
Significant Difference ◽  
The Pearl River

&lt;p&gt;Based on the field efforts in 2016 during a dry season (30 Nov-6 Dec) in the Pearl River Estuary (PRE)&amp;#65292;south China, this study aimed to investigate the tidal changes of phytoplankton variability (in terms of chlorophyll a) and their responses to multiple environmental factors.Time series analysis&amp;#65292;principal component analysis (PCA)&amp;#65292;Pearson correlation analysis, and Delft3D model were carried out. A significant difference was found in the tidal variations of dissolved nutrients, covering both a spring tide and neap tide . Moderate differences in salinity and suspended sediment played different roles in the nitrogen and phosphate. The negative correlations of salinity and nitrogen ecologically implied a stronger diluting-mixing effect than that of phosphate, which has a large impact on the water quality. The adsorption of phosphorus by sediment particles was stronger than that of nitrogen. Nitrogen was mainly contributed by river discharge. DIN was constrained by tide-river dynamics and their mutual increase-decline trend, and a new source was supplemented along the transport from river to sea. The weak correlation between PO&lt;sub&gt;4&lt;/sub&gt;&amp;#160;and salinity suggested a different source contribution of the terrestrial emission from coastal cities; the contribution of river discharge was less compared with nitrogen.&amp;#160;Over site, P-limitation&amp;#160;was detected and was more frequently resulted in eutrophication and even bloom events.&amp;#160;Characterizing the relationships among chlorophyll a, nutrients, and hydrological factors enables us to develop effective ecosystem management strategies, and to design studies more focused on ecological health and function.&lt;/p&gt;

Net Bottom Sediment Transport Pattern Related to Residual Currents in the Pearl River Estuary, South China

2016 ◽  
Author(s):  
Yao Wu ◽  
Wei Zhang ◽  
Mingkai Guan ◽  
Huanghao Hu
Keyword(s):  
Grain Size ◽  
Sediment Transport ◽  
Bottom Sediment ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Ocean Model ◽  
Pearl River ◽  
Residual Currents ◽  
The Pearl River Estuary ◽  
The Pearl River

In this study, the net bottom sediment transport pattern is measured and compared with flow pattern in the Pearl River Estuary (PRE). Based on 106 bottom sediment samples taken from the PRE, the spatial distribution of bottom sediment of mean grain size μ (mm), sorting coefficient σ, and skewness SK is calculated. Then the grain size trend analysis (GSTA) was used to detect the net bottom sediment transport characteristics. The bottom sediment is transported southward and southeastward in the upper part of the estuary and northward in the lower part, while a clockwise rotation trend occurs in the central part. Furthermore, a numerical flow model, based on Princeton Ocean Model (POM), is used to modulate the hydrodynamic conditions in the PRE. The simulated long-term bottom residual currents correlate well with the GSTA results, implying that the net bottom sediment transport is mainly controlled by the residual currents.

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