Landscape sensitivity to past and future climate: Solving the intermittency puzzle

景观对过去和未来气候的敏感性：解决间歇性难题

• 批准号: 2743977
• 金额: --
• 依托单位: Imperial College London
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2022
• 资助国家: 英国
• 起止时间: 2022 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2743977
• 关键词: Landscape; sensitivity; past; future; climate

Understanding how changing climate affects erosional processes that shape the planet's surface is a key goal for geoscientists. Constraints on the intermittency of water flux and sediment transport in catchments are rare, but are of critical importance in reaching this goal. The data that exist indicate that bankful sediment transport rates, if sustained, would imply millennial sediment fluxes orders of magnitude greater than that observed in depositional archives or from erosional estimates. Consequently, small reductions in the intermittency of fluvial transport, caused by enhanced storminess in a warming world, could significantly enhance erosion rates and sediment export. This project aims to solve the 'intermittency puzzle' by using a combination of field data from modern rivers; geological stratigraphy; and numerical modelling to provide new constraints on landscape and sediment routing system sensitivity to environmental change: 1) Using well constrained modern catchments in Greece, the student will calculate bankfull sediment transport capacities and water discharges, using published and new measurements of catchment geometry and sediment grain size. This locality is selected because its semi-arid climate is well-studied and because IODP data in the Corinth area have uniquely constrained Holocene sedimentation rates with exceptional fidelity. Flux estimates will be compared with Holocene depositional volumes and catchment average erosion rate estimates to calculate the ratio of actual sediment fluxes to potential bankful fluxes, were they to be sustained over the same time period - the sediment transport intermittency ratio. These sediment transport intermittencies will be directly compared with the present-day distribution of rainfall and historical data on the frequency of storm events. 2) These modern data sets will be compared critically to geological examples of arid systems. We will focus on Eocene fluvial deposits - the warmest Epoch of the Cenozoic. Well-studied exemplars in the Spanish Pyrenees will be selected as comparators. These systems have known depositional volumes, and well preserved channel architectures which enable bankful flow conditions to be reconstructed. Sediment transport intermittency will be compared to climate reconstructions for the mid and late Eocene and to modern examples. 3) Finally, the student will use a coupled model of a catchment-basin system, developed at Imperial with external collaborator Brooke, which includes rainfall intermittency and an infiltration threshold, to model sediment routing system response to rainfall variability. Predictions of how rainfall/storminess may evolve in the future for a range of scenarios will be used to forward model synthetic landscape evolution and erosional fluxes, using the geological data above to calibrate key inputs. The results will be used to solve the intermittency puzzle and identify catchment vulnerability to enhanced storminess.

了解气候变化如何影响形成地球表面的侵蚀过程是地球科学家的一个关键目标。对集水区水通量和泥沙输送间歇性的限制很少，但对实现这一目标至关重要。现有的数据表明，岸上的泥沙运移速度如果持续下去，将意味着千年泥沙通量比沉积档案或侵蚀估计中观察到的要大几个数量级。因此，在全球变暖的情况下，由于暴风雨的增加，河流输运间歇性的小幅减少可能会大大增加侵蚀速度和泥沙输出。该项目旨在通过结合现代河流的实地数据、地质地层学和数值模拟来解决“间歇性难题”，为景观和泥沙输送系统对环境变化的敏感度提供新的约束：1)使用希腊约束良好的现代集水区，学生将使用已公布的和新的集水区几何形状和沉积物粒度测量来计算堤岸的泥沙输送能力和排水量。之所以选择这个地点，是因为它的半干旱气候得到了充分的研究，而且科林斯地区的IODP数据具有独特的限制全新世沉积速率的非凡保真度。通量估算将与全新世沉积体积和集水区平均侵蚀速率估算进行比较，以计算实际泥沙通量与潜在泥沙通量的比率，如果它们在同一时间段--泥沙输送间歇比率--持续的话。这些泥沙输送间歇性将直接与目前的降雨量分布和风暴事件频率的历史数据进行比较。2)这些现代数据集将被严格地与干旱系统的地质例子进行比较。我们将重点研究始新世河流沉积--新生代最温暖的时代。西班牙比利牛斯山上经过充分研究的样本将被选为比较者。这些系统具有已知的沉积体积和保存良好的河道结构，使岸滩流动条件得以重建。泥沙输送间歇性将与始新世中期和晚期的气候重建以及现代例子进行比较。3)最后，学生将使用帝国理工学院与外部合作者布鲁克共同开发的集水流域系统的耦合模型，该模型包括降雨间歇和渗透阈值，以模拟泥沙输送系统对降雨变异性的响应。对未来一系列情景下降雨/风暴可能演变的预测将被用于建立合成地貌演变和侵蚀通量的模型，使用上述地质数据来校准关键输入。结果将被用来解决间歇性难题，并确定集水区对增强风暴的脆弱性。