Suspended particulate matter dynamics at the interface between an estuary and its adjacent coastal sea: Unravelling the impact of tides, waves and river discharge from 2015 to 2022 in situ high-frequency observations

IF 2.6 3区地球科学 Q2 GEOSCIENCES, MULTIDISCIPLINARY

Marine Geology Pub Date : 2024-04-02 DOI:10.1016/j.margeo.2024.107281

Romaric Verney , David Le Berre , Michel Repecaud , Alan Bocher , Tanguy Bescond , Coline Poppeschi , Florent Grasso

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引用次数: 0

Abstract

Suspended particulate matter (SPM) dynamics and exchange fluxes at the interface between a macrotidal estuary and its adjacent coastal sea were investigated from long-term high-frequency in situ observations. Optical and acoustic measurements were coupled to calculate SPM concentration over the whole water column using an existing acoustic inversion algorithm. A method was developed to distribute over the water column the surface and bottom calibrated equivalent particle diameters based on complementary ship-based surveys. Surface and bottom SPM show similar patterns in response to main forcings (tide, river discharge and waves), but present significantly higher concentrations near the bed. Increasing tidal ranges were responsible for higher tidal-median SPM concentrations, with spring/neap SPMC ratio varying from 2 to 3. This increase is driven by local resuspension during flood phase at the bottom, and low salinity turbid water flushed out from the estuary from mid-ebb to low tide at the surface. Increasing river discharge implies a downward shift of the estuarine turbidity maximum from the inner estuary to the mouth, and yields a 2-fold increase in both surface and bottom tidal-median concentration. Waves generated strong resuspension, with the highest SPM concentration recorded both at the surface and near the bed. Analysing SPM residual fluxes highlighted large up-estuary fluxes from low to moderate tidal ranges (below 6 m), and exporting seaward fluxes for higher tidal ranges, due to stronger mixing during spring tides. High river discharge enhanced stratification at the mouth and strengthened density circulation and up-estuary residual bottom circulation, resulting in larger up-estuary fluxes for all tidal ranges. Larger SPM concentrations along the tidal cycle during wave events yield high exporting fluxes.

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河口与邻近近海交界处的悬浮颗粒物动力学：从 2015 年到 2022 年的原位高频观测揭示潮汐、海浪和河流排水量的影响

通过长期高频原位观测，研究了大潮汐河口与邻近近岸海域交界处的悬浮颗粒物（SPM）动态和交换通量。将光学和声学测量结果结合起来，利用现有的声学反演算法计算整个水柱的 SPM 浓度。根据互补的船基勘测结果，开发了一种在水体中分布表层和底层校准等效颗粒直径的方法。表层和底层 SPM 对主要作用力（潮汐、河流排水量和波浪）的响应模式相似，但在海床附近的浓度明显更高。潮汐范围的增大导致了潮汐-中值 SPM 浓度的升高，春季/傍晚 SPMC 比值从 2 到 3 不等。这种升高是由底部洪水期的局部再悬浮以及河口从退潮中期到潮落时表面冲出的低盐度浑浊水造成的。河水排放量的增加意味着河口浊度最大值从河口内侧下移到河口，并导致河口表层和底层潮汐中值浓度增加 2 倍。波浪产生了强烈的再悬浮现象，在海面和海床附近都记录到了最高的 SPM 浓度。对 SPM 剩余通量的分析突出表明，在低到中等潮差（低于 6 米）范围内，SPM 大量流入河口，而在较高的潮差范围内，由于春潮期间混合作用较强，SPM 则向海输出。河流的高排水量增强了河口的分层，加强了密度环流和河口上游的残余底层环流，从而导致所有潮差范围的河口上游通量增大。在波浪事件期间，沿潮汐周期较大的 SPM 浓度产生了较高的输出通量。

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来源期刊

Marine Geology 地学-地球科学综合

CiteScore

6.10

自引率

6.90%

发文量

175

审稿时长

21.9 weeks

期刊介绍： Marine Geology is the premier international journal on marine geological processes in the broadest sense. We seek papers that are comprehensive, interdisciplinary and synthetic that will be lasting contributions to the field. Although most papers are based on regional studies, they must demonstrate new findings of international significance. We accept papers on subjects as diverse as seafloor hydrothermal systems, beach dynamics, early diagenesis, microbiological studies in sediments, palaeoclimate studies and geophysical studies of the seabed. We encourage papers that address emerging new fields, for example the influence of anthropogenic processes on coastal/marine geology and coastal/marine geoarchaeology. We insist that the papers are concerned with the marine realm and that they deal with geology: with rocks, sediments, and physical and chemical processes affecting them. Papers should address scientific hypotheses: highly descriptive data compilations or papers that deal only with marine management and risk assessment should be submitted to other journals. Papers on laboratory or modelling studies must demonstrate direct relevance to marine processes or deposits. The primary criteria for acceptance of papers is that the science is of high quality, novel, significant, and of broad international interest.