Quantifying the response of rapidly eroding landscapes to climate change with cosmogenic nuclides

在地球上的许多地区，全球变暖和水文循环的相关变化影响了河流的总径流量以及洪水的频率和规模。流量的变化很可能会立即影响河流的输送能力，但气候变化如何影响山坡上沉积物的供应还不清楚。在这个项目中，我们要测量宇宙成因的核素浓度在填补梯田的亚穆纳河，印度，以确定随时间变化的山坡侵蚀率，并解开如何在喜马拉雅山迅速侵蚀景观在过去的气候变化作出反应。我们将补充我们的地球化学方法与重建的几何形状和体积的山谷填充，实地测绘和地形建模的基础上。几何重建使我们能够评估泥沙存储的空间分布和时间变化的纵向渠道剖面，这影响了输沙能力。此外，我们将使用不同的地质年代学方法，以获得一个准确的加积和切割周期的年表，并结合联合收割机这些数据与沉积学观察推断的来源和起源的沉积物，并与古水文重建的基础上稳定同位素的叶蜡。这些数据，结合我们的体积估计和山坡的侵蚀历史，使我们能够重建沉积物预算随着时间的推移，并绘制一个全面的图片的环境条件在山谷加积期间，并测试现有的模型喜马拉雅景观如何应对气候变化。该项目的预期结果将有助于评估当今气候变化的影响，并评估第四纪气候波动对喜马拉雅山侵蚀的影响以及晚新生代气候变化的假设反馈。

In many regions on Earth, Global Warming and the associated changes in the hydrological cycle affect total river runoff and the frequency and magnitude of floods. Changes in discharge are likely to immediately affect the transport capacity of rivers, but how climatic changes affect the supply of sediments from hilllopes is not well understood. In this project, we want to measure cosmogenic nuclide concentrations in fill terraces of the Yamuna River, India, to determine the temporal variability of hillslope erosion rates and to unravel how a rapidly eroding landscape in the Himalaya has responded to climatic changes in the past. We will supplement our geochemical approach with a reconstruction of the geometry and volume of the valley fill, based on field mapping and topographic modeling. The geometrical reconstruction allows us to assess the spatial distribution of sediment storage and temporal changes in the longitudinal channel profile, which affects the sediment transport capacity. Furthermore, we will use different geochronological methods to obtain an accurate chronology of the aggradation-and-incision cycle, and combine these data with sedimentological observations for inferring the source and origin of the sediments, and with paleo-hydrologic reconstructions based on stable isotopes in leaf waxes. These data, combined with our volume estimate and the erosional history of hillslopes, allow us to reconstruct the sediment budget through time and draw a comprehensive picture of the environmental conditions during the period of valley aggradation and to test existing models of how Himalayan landscapes respond to climate change. The expected results of this project will help assessing the impacts of present-day climate change, and evaluating the consequences of Quaternary climate fluctuations for erosion in the Himalaya and the postulated feedbacks on Late Cenozoic climate change.