Role of delta-front erosion in sustaining salt marshes under sea-level rise and fluvial sediment decline
Role of delta-front erosion in sustaining salt marshes under sea-level rise and fluvial sediment decline
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DOI：
10.1002/lno.11432
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发表时间：
2020-03-18
影响因子：
4.5
通讯作者：
Gao, Shu
中科院分区：
文献类型：
--
作者：
Yang, Shi Lun;Luo, Xiangxin;Gao, Shu
海平面加速上升和河流沉积物供应减少被广泛认为是导致全球三角洲沼泽及其宝贵生态系统服务丧失的原因。然而，鲜为人知的是，在何种程度上，相关的侵蚀向海三角洲前缘可以提供沉积物，以维持盐沼。在这里，我们提供了来自长江三角洲中峰潮带的数据，表明尽管海平面相对快速上升（类似于每年10毫米（-1））并且长江沉积物供应减少了70%以上，但沼泽仍继续垂直和横向增生。沼泽湿地退化的速度比河流沉积物减少的速度慢，这表明沉积物的另一个来源。我们发现，在有利的条件下（例如，中高潮潮差、强潮汐流、洪水优势、沉积物沉降滞后/冲刷滞后效应以及高潮水位上升），三角洲前缘侵蚀实际上可以向沼泽提供沉积物，从而使沼泽的增长率与相对海平面上升保持平衡。全球三角洲的比较表明，沉积物再动员维持沼泽的能力取决于沿海过程，并且在世界主要三角洲之间差异超过一个数量级。
Accelerating sea-level rise and decreasing riverine sediment supply are widely considered to lead to global losses of deltaic marshes and their valuable ecosystem services. However, little is known about the degree to which the related erosion of the seaward delta front can provide sediments to sustain salt marshes. Here, we present data from the mesomacrotidal Yangtze Delta demonstrating that marshes have continued to accrete vertically and laterally, despite rapid relative sea-level rise (similar to 10 mm yr(-1)) and a > 70% decrease in the Yangtze River sediment supply. Marsh progradation has decelerated at a lower rate than fluvial sediment reduction, suggesting an additional source of sediment. We find that under favorable conditions (e.g., a mesomacrotidal range, strong tidal flow, flood dominance, sedimentary settling lag/scour lag effects, and increasing high-tide level), delta-front erosion can actually supply sediment to marshes, thereby maintaining marsh accretion rates in balance with relative sea-level rise. Comparison of global deltas illustrates that the ability of sediment remobilization to sustain marshes depends on coastal processes and varies by more than an order of magnitude among the world's major deltas.