Bridging Timescales of Climate and Vegetation Change Effects on Denudation: A Coupled Modeling Approach

该提案是我们在EarthShape第1阶段进行的工作的延续。 我们的第一阶段研究量化了自末次冰期以来气候和植被的变化，以呈现地球形状研究区域受影响的地形和侵蚀速率。我们发现在过去的21万年，植被和侵蚀的显着变化，和非线性响应和阈值侵蚀植被覆盖变化。基于这些结果，新生代的剧烈环境和构造变化促使我们在第二阶段跨越更长（百万年）的时间尺度，以评估更大幅度的气候变化对智利沿海科迪勒拉植被相关的风化和侵蚀的影响。我们通过测试总体假设来做到这一点，即如果新生代大气中的二氧化碳水平以及更温暖和更潮湿的古气候（始新世-渐新世边界）减少了一个数量级，到现在的值更低，然后：（1）这种变化将导致新生代植物生产力和植被覆盖率显著下降，（2）植被的变化将从根本上改变侵蚀速率，植物促进的风化作用将减弱。因此，今天的地形可能包含过去植被过程的强烈印记。我们对这一假设的探索和评估将建立在我们自己和其他人在第一阶段取得的技术成就的基础上。我们将采用耦合动态植被（LPJ-GUESS）和景观演化（LandLab）模型，该模型将由预测的古气候变化（ECHAM 5）在过去的34马。我们的方法的整体和前沿是将植被和景观演变模型联系起来，以计算生物（植物促进）和非生物风化的变化。由此，我们将：a）评估瞬时植被变化如何影响流域剥蚀率、地形和深层风化; B）确定植被调节的侵蚀和风化对古大气CO2、降水和温度变化的敏感性; c）将现有的第1阶段和新的第2阶段土壤、地球化学（剥蚀率）、地质和生态数据从其他项目整合到我们的建模框架中。

This proposal is a continuation of our work conducted in EarthShape phase 1. Our phase 1 research quantifies how climate and vegetation changes since the Last Glacial Maximum to present impacted topography and erosion rates in the EarthShape study areas. We found significant changes in vegetation and erosion over the last 21 ka, and a non-linear response and thresholds in erosion to vegetation cover change. Based on these results, the dramatic environmental and tectonic changes of the Cenozoic motivate us in this second phase to bridge across longer (million year) timescales to evaluate larger magnitude climate change effects on vegetation related weathering and erosion in the Chilean Coastal Cordillera. We do this by testing the overarching hypothesis that if atmospheric CO2 levels and warmer and wetter paleoclimate in the Cenozoic (Eocene-Oligocene boundary) decreased by an order of magnitude to lower values towards present then: (1) This change would drive a marked decrease in plant productivity and vegetation cover over the Cenozoic, and (2) The vegetation changes would fundamentally alter erosion rates and plant-facilitated weathering would decrease. Thus, present day topography may contain a strong imprint of past vegetation processes. Our exploration and evaluation of this hypothesis will build upon our own and others technical achievements of the first phase. We will apply a coupled dynamic vegetation (LPJ-GUESS) and a landscape evolution (LandLab) model that will be driven by predicted paleoclimate changes (ECHAM5) over the last 34 Ma. Integral and cutting edge to our approach is linking the vegetation and landscape evolution models to calculate changes in biotic (plant facilitated) and abiotic weathering. From this, we will: a) evaluate how transient vegetation changes influence catchment denudation rates, topography, and deep weathering; b) identify the sensitivity of vegetation modulated erosion and weathering to changes in paleo atmospheric CO2, precipitation, and temperature, and c) integrate existing phase 1, and new phase 2 soil, geochemical (denudation rate), geologic, and ecologic data from other projects into our modeling framework.