The estuarine turbidity maximum (ETM) under strong tidal dynamics (during spring tides) was investigated along the Deepwater Navigation Channel (DNC) in the North Passage (NP) of the Changjiang River Estuary (CRE) in wet and dry seasons of 2016, 2017 and 2018. The observed water current, salinity, stratification and suspended sediment concentration (SSC) were illustrated and analyzed. Results show that the SSC was lower in wet seasons than dry seasons in 2016 and 2017 because of the weak influence of typhoons before observations in wet seasons. On the contrary, the SSC was higher in the wet season than the dry season in 2018 because of the strong influence of typhoons in the wet season. Our observations challenged the common perspective that SSC in the NP is higher in wet seasons than dry seasons, because the magnitudes of SSC were found to be easily influenced by strong winds before observations. The along-channel distribution of high SSC was determined by the location of salt wedge, and consequently, the ETM was further upstream in dry seasons than wet seasons. The observed SSC was more concentrated in lower water layers in wet seasons (“exponential” profile) than dry seasons (“linear” profile). This seasonal difference of vertical SSC was related to the flocculation setting velocity influenced by temperature rather than the weak stratification during spring tides. Moreover, on the basis of the net water/sediment transport and flux splitting, large river discharge and a low-SSC condition could reduce siltation in the middle DNC. The former vanished the convergence of water transport, and the latter reduced landward tidal pumping sediment transport. Sediment trapping and siltation in the dry seasons occurred in the seaward segment of the upper reach because of the decrease in the river discharge.

中文翻译：

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强潮汐动力学下的季节性河口最大浊度：长江口三年观测

2016、2017年干湿季长江口北航道（NP）深水航道（DNC）沿线强潮汐动力学（大潮时）河口最大浊度（ETM）研究和 2018. 对观测到的水流、盐度、分层和悬浮泥沙浓度 (SSC) 进行了说明和分析。结果表明，由于雨季观测前台风影响较弱，2016年和2017年雨季SSC低于旱季。相反，由于雨季台风的强烈影响，2018年雨季SSC高于旱季。我们的观察挑战了普遍的观点，即 NP 的 SSC 在雨季高于旱季，因为在观测之前发现SSC的震级很容易受到强风的影响。高SSC的沿河道分布由盐楔的位置决定，因此ETM在旱季比雨季更上游。与旱季（“线性”剖面）相比，观测到的 SSC 在雨季（“指数”剖面）中更集中在较低的水层中。垂直SSC的这种季节性差异与受温度影响的絮凝凝结速度有关，而不是与大潮期间的弱分层有关。此外，在净水/泥沙输送和通量分裂的基础上，大河流流量和低 SSC 条件可以减少 DNC 中部的淤积。前者消失了水运的汇流，后者减少了向陆地潮汐抽吸沉积物的输送。由于河流流量减少，上游向海段出现旱季截沙淤积现象。