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

这项建议是我们在EarthShape第一阶段进行的工作的继续。我们的第一阶段研究量化了自上一次冰盛期以来气候和植被的变化，以呈现EarthShape研究区域受影响的地形和侵蚀速率。我们发现，在过去的21ka期间，植被和侵蚀发生了显著变化，侵蚀对植被覆盖变化的响应和阈值是非线性的。基于这些结果，新生代巨大的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，评估更大规模的气候变化对智利沿海科迪勒拉海岸植被风化和侵蚀的影响。我们通过检验最重要的假设来实现这一点，即如果新生代(始新世-渐新世边界)的大气二氧化碳水平和更温暖、更潮湿的古气候向现在下降一个数量级，那么：(1)这种变化将导致新生代植物生产力和植被覆盖率的显著下降，(2)植被变化将从根本上改变侵蚀速率，植物促进的风化作用将减少。因此，今天的地形可能包含了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第一阶段的技术成果的基础上。我们将应用一个耦合的动态植被(LPJ-GUESS)和景观演化(LandLab)模型，该模型将由过去34 Ma的预测古气候变化(ECHAM5)驱动。我们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(植物促进的)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集水区剥蚀率、地形和深度风化；b)确定植被调制侵蚀和风化对古大气CO2、降水和温度变化的敏感性；c)将现有的第一阶段和新的第二阶段土壤、地球化学(剥蚀率)、地质和生态数据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.