Characteristics and Driving Mechanisms of Mixing and Stratification in the North Passage of the Changjiang Estuary, China

2021 ◽  
Vol 38 (1) ◽  
Author(s):  
Yajun Wang ◽  
Chenjuan Jiang ◽  
Heqin Cheng ◽  
Weihua Li ◽  
Lizhi Teng
Keyword(s):  
Changjiang Estuary ◽  
The Changjiang Estuary ◽  
The North ◽  
Driving Mechanisms

Numerical Analysis of Ebb Water Split Ratio of the South and North Branch in the Changjiang Estuary

2013 ◽  
Vol 807-809 ◽  
pp. 1624-1627
Author(s):  
Ji Zhong Yang ◽  
Jie Gu ◽  
Dan Qing Ma ◽  
Xiao Li Wang ◽  
Tian Hu ◽  
...  
Keyword(s):  
Spring Tide ◽  
Changjiang Estuary ◽  
The South ◽  
The Changjiang Estuary ◽  
Hydrodynamic Analysis ◽  
The North ◽  
Split Ratio ◽  
Calculation Results ◽  
Set Up ◽  
The One

The change of water split ratio has important impacts on the fluvial process, saltwater intrusion and navigation in estuary area. A 2D hydrodynamics numerical model of the Changjiang Estuary was set up using Delft3D-FLOW. The calculation results are consistent well with the real measured data, which indicates that the model can be used in hydrodynamic analysis. Simulation results show that the ebb water split ratio of the North Branch in the flood season is larger than that in the dry season, while the situation of the South Branch is opposite. Under the condition of different tidal types, the ebb water split ratio for the North Branch is maximum during the spring tide, and minimum during the neap tide, while the one during the middle tide takes the second place.

scholarly journals Impacts of the Qingcaosha Reservoir on saltwater intrusion in the Changjiang Estuary

2021 ◽  
Vol 4 (1) ◽  
pp. 17-35
Author(s):  
Zhangliang Ding ◽  
Jianrong Zhu ◽  
Hanghang Lyu
Keyword(s):  
Saltwater Intrusion ◽  
Neap Tide ◽  
Spring Tide ◽  
Changjiang Estuary ◽  
Water Diversion ◽  
The Changjiang Estuary ◽  
The North ◽  
Salinity Increase ◽  
Hydrodynamic Processes ◽  
Changxing Island

The massive Qingcaosha Reservoir (QCSR) is located in the Changjiang Estuary along the northwest coast of Changxing Island. The reservoir significantly narrowed the upper reaches of the North Channel and deepened the channel near the reservoir. These topographical changes inevitably influenced hydrodynamic processes and saltwater intrusion in the estuary. A well-validated model was employed to investigate the influence of the QCSR on saltwater intrusion in the Changjiang Estuary. The model results showed that the narrowed upper reaches of the North Channel decreased the water diversion ratio and thus increased salinity in the North Channel. During the moderate tide after neap tide, the salinity decreased at the water intake of the QCSR because saltwater intrusion was obstructed at flood slack at the surface, while the salinity increase during the moderate tide after spring tide was mainly due to the intensified saltwater intrusion during spring tide. The deepening of the channel near the QCSR resulted in an increased water diversion ratio, and the salinity in the Eastern Chongming Shoal decreased by more than 0.5 psu during spring tide; however, the saltwater intrusion was enhanced due to the strengthened baroclinic force, which is proportional to the water depth. During neap tide, the salinity in the entire North Channel decreased because of a 1.4% increase in the water diversion ratio of the North Channel and the relatively weak tide.

scholarly journals Wind-driven stratification patterns and dissolved oxygen depletion off the Changjiang (Yangtze) Estuary

2020 ◽  
Vol 17 (10) ◽  
pp. 2875-2895
Author(s):  
Taavi Liblik ◽  
Yijing Wu ◽  
Daidu Fan ◽  
Dinghui Shang
Keyword(s):  
Dissolved Oxygen ◽  
Summer Monsoon ◽  
Changjiang Estuary ◽  
Wind Forcing ◽  
Coastal Current ◽  
The South ◽  
The Changjiang Estuary ◽  
Water Intrusion ◽  
The North ◽  
Hypoxic Area

Abstract. Multiple factors have been accused of triggering coastal hypoxia off the Changjiang Estuary, and their interactions lead to high yearly variation in hypoxia development time window and distribution extent. Two oceanographic cruises, conducted in July 2015 and August–September 2017, were complemented by river discharge, circulation simulation, remotely sensed wind, salinity and sea level anomaly data to study the dissolved oxygen (DO) depletion off the Changjiang Estuary from synoptic to interannual timescales. Intensification of the Chinese Coastal Current and Changjiang Diluted Water (CDW) spreading to the south together with coastal downwelling caused by the northerly wind was observed in the summer of 2015. This physical forcing led to a well-ventilated area in the north and a hypoxic area of 1.3×104 km2 in the south, while in 2017 the summer monsoon (southerly winds) induced offshore transport in the surface layer that caused a subsurface intrusion of Kuroshio-derived water to the shallower areas (<10 m depth) in the north and upwelling in the south. Wind-driven Ekman surface flow and reversal of the geostrophic current related to the upwelling compelled alteration of the Chinese Coastal Current. Consequently, intense hypoxia (DO down to 0.6 mg L−1) starting from 4 to 8 m depth connected to CDW and deep water intrusion in the north and coastal hypoxia linked to the upwelling in the south were observed in 2017. Distinct situations of stratification and DO distributions can be explained by wind forcing and concurrent features in surface and deep layer circulation, upwelling and downwelling events. Enhanced primary production in the upper layer of the CDW or the upwelled water determines the location and extent of DO depletion. Likewise, the pycnocline created by Kuroshio subsurface water intrusion is an essential precondition for hypoxia formation. Wind forcing largely controls the interannual change of hypoxic area location and extent. If the summer monsoon prevails, extensive hypoxia more likely occurs in the north. Hypoxia in the south occurs if the summer monsoon is considerably weaker than the long-term mean.

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