期刊
EARTH SURFACE DYNAMICS
卷 9, 期 2, 页码 183-203出版社
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/esurf-9-183-2021
关键词
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资金
- USGS Mendenhall Research Fellowship program
- USGS Coastal and Marine Geology program
- Federal funds under National Oceanic and Atmospheric Administration (NOAA) [NA18OAR4170083]
- Virginia Sea Grant College Program [721557]
- NOAA National Sea Grant College Program
- US Department of Commerce
Barrier coasts, including barrier islands and beach-ridge plains, exhibit diverse morphologies over multi-decadal scales, with modern sea-level rise and sediment availability playing critical roles in shaping their evolution. This study explores the quantitative thresholds controlling barrier system behavior, revealing that subtle changes in sediment fluxes could significantly impact barrier morphology. The research suggests that the balance between relative sea-level rise and sediment flux largely determines the transitions between different barrier states, highlighting the importance of understanding these dynamics in the face of rising sea levels.
Barrier coasts, including barrier islands, beach-ridge plains, and associated landforms, can assume a broad spectrum of morphologies over multi-decadal scales that reflect conditions of sediment availability, accommodation, and relative sea-level rise. However, the quantitative thresholds of these controls on barriersystem behavior remain largely unexplored, even as modern sea-level rise and anthropogenic modification of sediment availability increasingly reshape the world's sandy coastlines. In this study, we conceptualize barrier coasts as sediment-partitioning frameworks, distributing sand delivered from the shoreface to the subaqueous and subaerial components of the coastal system. Using an idealized morphodynamic model, we explore thresholds of behavioral and morphologic change over decadal to centennial timescales, simulating barrier evolution within quasi-stratigraphic morphological cross sections. Our results indicate a wide diversity of barrier behaviors can be explained by the balance of fluxes delivered to the beach vs. the dune or backbarrier, including previously understudied forms of transgression that allow the subaerial system to continue accumulating sediment during landward migration. Most importantly, our results show that barrier state transitions between progradation, crossshore amalgamation, aggradation, and transgression are controlled largely through balances within a narrow range of relative sea-level rise and sediment flux. This suggests that, in the face of rising sea levels, subtle changes in sediment fluxes could result in significant changes in barrier morphology. We also demonstrate that modeled barriers with reduced vertical sediment accommodation are highly sensitive to the magnitude and direction of shoreface fluxes. Therefore, natural barriers with limited sediment accommodation could allow for exploration of the future effects of sea-level rise and changing flux magnitudes over a period of years as opposed to the decades required for similar responses in sediment-rich barrier systems. Finally, because our model creates stratigraphy generated under different input parameters, we propose that it could be used in combination with stratigraphic data to hindcast the sensitivity of existing barriers and infer changes in prehistoric morphology, which we anticipate will provide a baseline to assess the reliability of forward modeling predictions.
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