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。地球表面易受气候、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地貌的演变。然而，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，目前尚不清楚。这一知识空白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，有已发表的证据表明，陆上气候强迫和近海沉积档案之间存在直接响应：在末次冰消期的陆上干旱化之后，浊积岩沉积厚度和频率在海上急剧减少。该项目旨在确定风化、侵蚀和沉积物输出到海洋的水文和植被的变化，从末次盛冰期（LGM）到目前的沿着智利海岸。为了实现这一目标，我们将沉积系统研究，地球化学和生物学的学科联系起来，共同探索水文和植被变化与地球表面过程之间的反馈，在大的空间（智利海岸）和时间（LGM到全新世）尺度上。我们假设，冰消期气候变化对智利景观的影响是强烈调制通过植被的存在。因此，我们认为气候/水文和植被变化与风化、侵蚀和沉积物输出变化之间存在时间滞后。我们建议通过应用一种独特的新型最先进的代理组合来测试这一假设，该代理组合允许检测植被和水文的变化（通过脂类生物标志物分析及其δ 13 C和δ D同位素组成）、风化作用（通过使用锂稳定同位素，δ 7 Li），和侵蚀（通过使用新的宇宙成因的流星10 Be/9 Be的比例），随后冰消期干旱化。在第一个工作包（WP 1），我们将确定这些代理沿着智利气候梯度的演变，现代侵蚀产品采样从核心顶部的河流和近海表层沉积物的现今空间差异。在WP 2中，我们使用相同的方法对独立日期的海洋沉积档案，提供必要的沉积遗产，以重建这些代理从末次冰期到现在的时间动态，因为在空间上有代表性的档案大多不存在陆上。这种现代校准（WP 1）与古记录（WP 2）相结合，将使我们能够识别和机械地了解变化的来源，以及植被，风化，侵蚀和沉积物出口到海洋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.