Collaborative Research: Timescales and drivers of floodplain disequilibrium at climatic transitions

合作研究：气候转变时洪泛区不平衡的时间尺度和驱动因素

• 批准号: 2114771
• 负责人: Isaac Larsen
• 金额: $ 7.84万
• 依托单位: University of Massachusetts Amherst
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-05-01 至 2025-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2114771&HistoricalAwards=false
• 关键词: Collaborative; Research; Timescales; drivers; floodplain

Rivers and floodplains significantly influence the landscapes and environments through which they pass. These systems exhibit a range of forms and characteristics (morphologies) controlled by a balance between the availability of unconsolidated rock (sediment) and the river’s capacity to transport that sediment. As climate exerts a major control on these variables, floodplain morphologies are expected to undergo major changes as Earth’s climate warms. Under a warming climate, sediment supply often declines relative to transport capacity and narrowing floodplains are characterized by vertical cutting through older deposits creating stair-stepped landscape features called river terraces. The goal of this study is to deepen our understanding of how floodplains have responded to different magnitudes and timescales of climatic changes in the past to enhance our ability to predict the extent to which they will change in the future. This goal will be achieved by determining the timing of river terrace formation and comparing it to known climate shifts throughout Earth’s recent geological past. The project also supports a summer workshop on landscape evolution for middle school girls from historically underrepresented groups, the development of an accessible undergraduate virtual field project on terrace formation, and the facilitation of a community field workshop to share project results.Specific research questions include: (1) What duration and intensity of climatic change is required to drive significant changes to floodplain morphology? (2) How long does it take for floodplains to establish new, stable morphologies after significant climate-driven changes? (3) To what extent do non-climatic mechanisms counter or enhance climatic controls on floodplain processes? These questions will be addressed by resolving the timing of ~14,000 years of floodplain aggradation and degradation preserved in river terraces in eastern Scotland and comparing them against the timing of major and minor climatic transitions and glaciations. Eastern Scotland is an ideal location to undertake this work because it is tectonically inactive, has an excellent climate chronology, has undergone both continental ice sheet and alpine glaciation, and contains river terrace successions. The terrace chronology will be developed using radiocarbon, optically stimulated luminescence, and cosmogenic nuclide exposure dating. A comparison of the timing and duration of river morphology changes between field sites with the same climatic and glacial history, but with different catchment properties, will be undertaken to determine how non-climatic variables influence aggradation and degradation cycles. The research will also address the role of prior glacial erosion on influencing floodplain morphology and modern sediment routing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

河流和洪泛区显著影响其所经过的景观和环境。这些系统表现出一系列的形式和特点（形态）之间的可用性松散的岩石（沉积物）和河流的能力，运输沉积物的平衡控制。由于气候对这些变量施加了重大控制，随着地球气候变暖，洪泛平原的形态预计将发生重大变化。在气候变暖的情况下，沉积物供应往往相对于输送能力下降，河漫滩变窄，其特点是垂直切割较老的沉积物，形成阶梯状的景观特征，称为河流阶地。这项研究的目的是加深我们对洪泛区如何应对过去不同程度和时间尺度的气候变化的理解，以提高我们预测未来变化程度的能力。这一目标将通过确定河流阶地形成的时间并将其与地球最近地质历史中已知的气候变化进行比较来实现。该项目还支持一个夏季讲习班的景观演变的中学女生从历史上代表性不足的群体，一个访问的本科生虚拟领域的梯田形成项目的发展，并促进社区实地工作坊分享项目成果。具体的研究问题包括：（1）什么样的持续时间和强度的气候变化需要驱动显着的变化洪泛区形态？(2)在重大的气候变化之后，洪泛平原需要多长时间才能建立新的稳定的地貌？(3)在何种程度上非气候机制对抗或增强气候对洪泛区过程的控制？这些问题将通过解决约14,000年的洪泛平原加积和退化的时间保存在苏格兰东部的河流阶地，并将其与主要和次要的气候转变和冰川的时间进行比较来解决。苏格兰东部是进行这项工作的理想地点，因为它是构造不活跃，有一个很好的气候年表，经历了大陆冰盖和高山冰川作用，并包含河流阶地继承。阶地年代学将利用放射性碳、光激发光和宇宙成因核素暴露测年法来确定。将对具有相同气候和冰川历史但具有不同集水特性的野外地点之间河流形态变化的时间和持续时间进行比较，以确定非气候变量如何影响沉积和退化周期。该研究还将解决先前冰川侵蚀对影响洪泛区形态和现代沉积物路由的作用。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。