Controls on the distribution of cosmogenic 10Be across shore platforms
Controls on the distribution of cosmogenic 10Be across shore platforms
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DOI：
10.5194/esurf-5-67-2017
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发表时间：
2017-01-26
影响因子：
3.4
通讯作者：
Ellis, Michael A.
中科院分区：
文献类型：
--
作者：
Hurst, Martin D.;Rood, Dylan H.;Ellis, Michael A.
量化一系列时间尺度上悬崖海岸的侵蚀率对于了解海岸变化的驱动因素和过程以及评估未来悬崖退缩带来的风险至关重要。历史记录最多涵盖过去 150 年； Be-10 等宇宙成因同位素可以让我们进一步回顾过去，以评估千年时间尺度上的沿海变化。宇宙成因同位素在地球表面附近原位积累，并在过去三十年中被广泛用于量化陆地景观的侵蚀率、埋藏日期和地表暴露年龄。最近，在岩石海岸环境中的应用已经量化了大规模消耗事件的时间，确定了悬崖退缩的长期平均速率，并揭示了海岸平台的暴露历史。在这篇文章中，我们开发并探索了 10Be 在侵蚀海岸平台上积累的数值模型。在一系列数值实验中，我们研究了地形和水屏蔽、动态平台侵蚀过程、海滩覆盖的存在和变化以及侵蚀的不均匀分布对 Be-10 跨岸平台分布的影响。结果表明，考虑到相对海平面变化和潮汐，Be-10 的浓度对悬崖退缩的速度很敏感。地形屏蔽和海滩覆盖等因素会降低平台上 Be-10 的浓度，如果不加以考虑，可能会导致悬崖退缩率被高估。 Be-10 在海岸平台上的分布形状可以潜在地揭示悬崖后退率随着时间的推移是下降还是加速。岸上平台中 Be-10 的测量具有巨大的潜力，可以让我们量化悬崖退缩和平台侵蚀的长期速率。
Quantifying rates of erosion on cliffed coasts across a range of timescales is vital for understanding the drivers and processes of coastal change and for assessing risks posed by future cliff retreat. Historical records cover at best the last 150 years; cosmogenic isotopes, such as Be-10 could allow us to look further into the past to assess coastal change on millennial timescales. Cosmogenic isotopes accumulate in situ near the Earth surface and have been used extensively to quantify erosion rates, burial dates and surface exposure ages in terrestrial landscapes over the last 3 decades. More recently, applications in rocky coast settings have quantified the timing of mass wasting events, determined long-term averaged rates of cliff retreat and revealed the exposure history of shore platforms. In this contribution, we develop and explore a numerical model for the accumulation of 10Be on eroding shore platforms. In a series of numerical experiments, we investigated the influence of topographic and water shielding, dynamic platform erosion processes, the presence and variation in beach cover, and heterogeneous distribution of erosion on the distribution of Be-10 across shore platforms. Results demonstrate that, taking into account relative sea level change and tides, the concentration of Be-10 is sensitive to rates of cliff retreat. Factors such as topographic shielding and beach cover act to reduce Be-10 concentrations on the platform and may result in overestimation of cliff retreat rates if not accounted for. The shape of the distribution of Be-10 across a shore platform can potentially reveal whether cliff retreat rates are declining or accelerating through time. Measurement of Be-10 in shore platforms has great potential to allow us to quantify long-term rates of cliff retreat and platform erosion.