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 (∼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.

中文翻译：

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海平面上升和河流沉积物下降条件下三角洲前缘侵蚀在维持盐沼中的作用

人们普遍认为，加速海平面上升和减少河流沉积物供应会导致三角洲沼泽及其宝贵的生态系统服务的全球损失。然而，关于向海三角洲前缘的相关侵蚀可以提供沉积物以维持盐沼的程度知之甚少。在这里，我们提供了来自中巨潮长江三角洲的数据，表明尽管相对海平面迅速上升（~10 mm yr-1）并且长江沉积物供应减少了 > 70%，但沼泽地继续垂直和横向增生。沼泽进积的减速速度低于河流沉积物减少的速度，这表明有额外的沉积物来源。我们发现，在有利条件下（例如，中巨潮范围、强潮汐流、洪水优势、沉积沉降滞后/冲刷滞后效应，和增加高潮位），三角洲前缘侵蚀实际上可以为沼泽提供沉积物，从而使沼泽增生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的差异超过一个数量级。