SECCO- Chile: The coupled vegetation, weathering, erosion, and sediment-export response to climate change unravelled from novel proxies in Chilean marine sediment

了解景观对气候变化的响应是当今地球科学的一个核心问题，因为预计未来降水模式和强度将发生重大变化。地球表面很容易受到气候、水文、植被、风化、侵蚀和沉积物沉积之间复杂反馈的影响，这些反馈影响着我们赖以生存的景观的演变。然而，目前尚不清楚植被、风化和侵蚀以及相关的沉积物动力学如何对气候变化做出反应。这种知识上的差距严重阻碍了将海洋沉积记录解释为气候和/或地表过程变化的档案。在智利，已发表的证据表明，陆上气候强迫与近海沉积档案之间存在直接反应：在末次冰期的陆上干旱化之后，近海浊积岩沉积物的厚度和频率大幅减少。该项目旨在确定智利海岸从末次冰期（LGM）到现在的水文和植被变化后，风化、侵蚀和沉积物向海洋出口的级联变化。为了实现这一目标，我们将沉积系统研究、地球化学和生物学等学科联系起来，共同探索大空间（智利海岸）和时间（LGM至全新世）尺度上水文和植被变化与地表过程之间的反馈关系。我们假设冰川消融气候变化对智利景观的影响是通过植被的存在而被强烈调节的。因此，我们认为气候/水文和植被的变化与风化、侵蚀和沉积物输出的变化之间存在时间滞后。为了验证这一假设，我们提出了一种新的、最先进的代用物的独特组合，这些代用物可以检测冰川消融后植被和水文（通过脂质生物标志物分析及其δ 13C和δ D同位素组成）、风化（通过Li稳定同位素、δ 7Li）和侵蚀（通过新的宇宙成因大气10Be/9Be比值）的变化。在第一个工作包（WP1）中，我们将通过采样来自岩心顶部的河流和近海表层沉积物的现代侵蚀产物，确定这些代用物沿着智利气候梯度演变的当今空间差异。在WP2中，我们使用相同的方法对独立定年的海洋沉积档案进行分析，这些档案提供了重建这些代用物从LGM到现在的时间动态所必需的沉积遗产，因为在空间上具有代表性的档案大多在陆上缺失。这种现代校准（WP1）与古记录（WP2）相结合，将使我们能够识别和机械地理解变化的来源，以及主要水文变化后植被、风化、侵蚀和沉积物向海洋输出的变化之间的时间领先和滞后。

Understanding landscape response to climate change is a central problem in the geosciences today, as substantial future changes in precipitation patterns and intensity are expected. Earth's surface is vulnerable to complex feedbacks between climate, hydrology, vegetation, weathering, erosion, and sediment deposition that affect the evolution of landscapes that we live on. However, precisely how vegetation, weathering and erosion, and associated sediment dynamics, respond to climate change is currently unknown. This gap in knowledge severely obstructs the interpretation of marine sedimentary records as archives of changes in climate and/or surface processes. In Chile, there is published evidence for a direct response between an onshore climatic forcing and the offshore sedimentary archive: following onshore aridification in the last deglacial, turbidite-deposit thickness and frequency strongly decreased offshore.This project seeks to identify the cascade of changes in weathering, erosion, and sediment export to the ocean following hydrologic and vegetation changes from the Last Glacial Maximum (LGM) to the present along the Chilean coast. To achieve this goal, we link the disciplines of sedimentary systems research, geochemistry, and biology to jointly explore the feedbacks between changes in hydrology and vegetation and Earth-surface processes over a large spatial (the Chilean coast) and temporal (LGM to Holocene) scale. We hypothesize that the impact of deglacial climate change on Chilean landscapes is strongly modulated through the presence of vegetation. Hence, we suggest that temporal lags occurred between changes in climate/ hydrology and vegetation, and changes in weathering, erosion, and sediment export.We propose to test this hypothesis by applying a unique combination of novel state-of-the-art proxies that allow the detection of changes in vegetation and hydrology (by lipid biomarker analysis and their delta 13C and delta D isotope composition), weathering (by using Li stable isotopes, delta 7Li), and erosion (by using novel cosmogenic meteoric 10Be/9Be ratios) that followed deglacial aridification. In a first work package (WP1), we will identify present-day spatial differences in the evolution of these proxies along the Chilean climatic gradient, by sampling modern erosion products from riverine and offshore surface sediment from core tops. In WP2, we use the same methods on independently dated marine sedimentary archives that provide the depositional legacy necessary to reconstruct the temporal dynamics of these proxies from the LGM to the present day, as spatially representative archives are mostly absent onshore. This modern calibration (WP1) in combination with the paleo-record (WP2) will allow us to identify and mechanistically understand the sources of variability in and the temporal leads and lags between changes in vegetation, weathering, erosion, and sediment export to the ocean following a major hydrological change.