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Relative influence of antecedent topography and sea‐level rise on barrier‐island migration
Sedimentology ( IF 3.5 ) Pub Date : 2020-09-11 , DOI: 10.1111/sed.12798
Justin L. Shawler 1 , Daniel J. Ciarletta 2 , Jennifer E. Connell 1 , Bianca Q. Boggs 3 , Jorge Lorenzo‐Trueba 4 , Christopher J. Hein 1
Affiliation  

The response of barrier islands to sea‐level rise is modulated by combinations of coastal processes, eco‐geomorphic feedbacks and structural controls, such as antecedent topography. Interactions among these drivers can lead to complex and non‐linear changes in island morphology and transitions between migrational, erosional or progradational states. This study seeks to constrain the morphological consequences of barrier islands migrating across complex antecedent topography in response to rising sea level. The stratigraphy of four barrier–backbarrier systems along the United States Mid‐Atlantic coast informs idealized geometries of diverse antecedent substrate. These outcomes are integrated into a cross‐shore morphodynamic model of barrier‐island migration to quantify the influence of this antecedent geology on barrier‐retreat behaviour. Additionally, this study explores the future response of specific barrier islands to various rates of sea‐level rise over multi‐decadal to millennial timescales. The results show that antecedent substrate slope plays a central role in barrier morphodynamic behaviour. In particular, migration across a subaqueous backbarrier ridge (for example, coastal barrier or dune deposits from earlier sea‐level highstands) can cause a succession of phase changes in a modern island. For example, the case studies illustrate that the steep slopes and decreased backbarrier accommodation associated with antecedent highs greater than 3 m in profile can greatly reduce island migration rates, effectively ‘pinning’ the island in place, even with sea‐level rise rates up to 6 mm yr−1. However, once the island migrates over the high, backbarrier accommodation increases, leading to enhanced overwash fluxes, more rapid landward migration, and possible drowning. Additionally, the results indicate that antecedent substrate may slow barrier‐island migration by providing sediment through both shoreface and inlet processes. The field and modelling insights from this study are presented as a conceptual model of the relative influence of various antecedent features on barrier‐island dynamics along sandy, siliciclastic coasts.

中文翻译:

前期地形和海平面上升对障碍岛迁移的相对影响

障碍物岛对海平面上升的响应受沿海过程,生态地貌反馈和结构控制(如前期地形)的组合调节。这些驱动因素之间的相互作用可能导致岛形形态复杂而非线性的变化,以及迁移,侵蚀或退化状态之间的转换。本研究旨在限制因海平面上升而在复杂的先前地形中迁移的隔离岛的形态学后果。美国中大西洋沿岸的四个屏障-后屏障系统的地层学为各种先质基质的理想几何形状提供了信息。这些结果被整合到屏障-岛屿迁移的跨岸地貌动力学模型中,以量化该先前地质对屏障-撤退行为的影响。此外,本研究还探讨了特定的障碍岛在数十年到千年尺度上对各种海平面上升速率的未来响应。结果表明,先前的底物斜率在屏障形态动力学行为中起着核心作用。尤其是,跨过水下屏障河脊的迁徙(例如,来自较早海平面高位的沿海屏障或沙丘沉积物)会导致现代岛屿中相继发生相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以极大地降低岛屿的迁移速度,有效地将岛屿固定在适当的位置,即使海平面上升速度高达年6毫米 这项研究探索了特定的障碍岛对未来几十年到千禧年尺度海平面上升速率的响应。结果表明,先前的底物斜率在屏障形态动力学行为中起着核心作用。尤其是,跨过水下屏障河脊的迁徙(例如,来自较早海平面高位的沿海屏障或沙丘沉积物)会导致现代岛屿中相继发生相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以极大地降低岛屿的迁移速度,有效地将岛屿固定在适当的位置,即使海平面上升速度高达年6毫米 这项研究探索了特定的障碍岛对未来几十年到千禧年尺度海平面上升速率的响应。结果表明,先前的底物斜率在屏障形态动力学行为中起着核心作用。尤其是,跨过水下屏障河脊的迁徙(例如,来自较早海平面高位的沿海屏障或沙丘沉积物)会导致现代岛屿中相继发生相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以大大降低岛屿的迁移率,有效地将岛屿“钉住”,即使海平面上升率达到年6毫米 结果表明,先前的底物斜率在屏障形态动力学行为中起着核心作用。尤其是,跨过水下屏障河脊的迁徙(例如,来自较早海平面高位的沿海屏障或沙丘沉积物)会导致现代岛屿中相继发生相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以大大降低岛屿的迁移率,有效地将岛屿“钉住”,即使海平面上升率达到年6毫米 结果表明,先前的底物斜率在屏障形态动力学行为中起着核心作用。尤其是,跨过水下屏障河脊的迁徙(例如,来自较早海平面高位的沿海屏障或沙丘沉积物)会导致现代岛屿中相继发生相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以极大地降低岛屿的迁移速度,有效地将岛屿固定在适当的位置,即使海平面上升速度高达年6毫米 早期海平面高位的沿海屏障或沙丘沉积物可能会导致现代岛屿发生一系列相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以大大降低岛屿的迁移率,有效地将岛屿“钉住”,即使海平面上升率达到年6毫米 早期海平面高位的沿海屏障或沙丘沉积物可能会导致现代岛屿发生一系列相变。例如,案例研究表明,陡峭的坡度和后壁障碍物的减少与前高大于3 m的轮廓相关联,可以大大降低岛屿的迁移率,有效地将岛屿“钉住”,即使海平面上升率达到年6毫米-1。但是,一旦岛屿在高处迁移,则后屏障的容纳量会增加,从而导致过度冲洗流量增加,更迅速的向岸迁移以及可能淹死。此外,结果表明,前期基质可能会通过沿岸面和入流过程提供沉积物,从而减慢隔离岛的迁移。这项研究的领域和建模见解是作为沙质硅质碎屑海岸沿岸屏障动态的各种相对特征的相对影响的概念模型。
更新日期:2020-09-11
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