Collaborative Research: Improved Cenozoic Paleoelevation Estimates for the Sierra Nevada, California: Linking Geodynamics and the Atmospheric Sciences

加州内华达山脉高了多久？这个问题是解开北美地质历史的最持久的挑战之一。许多研究认为内华达山脉在晚白垩纪（大约6500万到1亿年前）达到了高海拔，随后经历了有限的地表海拔上升。一组相反的研究认为始新世（大约3500万到5500万年前）的内华达山脉海拔低，起伏弱，始新世后的地表隆起脉冲与上新世地壳根部的剥离有关，导致了该山脉的现代海拔升高。这些不同的观点体现了北美构造演化的根本不同的理论。内华达山脉自始新世以来一直是一个持续高地形地区的解释的主要证据来源是稳定的同位素和叶形古高度计技术。然而，最近一系列的大气动力学研究对这些解释提出了挑战。这些研究表明，目前解释降水同位素比率代用记录的框架是基于对大气的假设，这些假设通常不适用于内华达山脉，或者没有适当考虑到古气候变化。该项目的目标是将地球动力学研究、大气动力学和古气候建模的最新方法结合起来，从而大大提高对内华达山脉古高程数据的解释，从而提高对该山脉地表高程历史的理解。该项目将严格评估内华达山脉周围的空气包裹轨迹，以及一系列大气条件下相关的降水同位素和焓分布。这些数据将来自于水同位素支持的大气环流模式对始新世到现在的古气候情景的模拟套件，以及在这段时间内北美西部的一系列拟议的地形设置。研究结果将改善对整个新生代内华达山脉地形的定量限制，特别是对晚新生代地表隆起潜力的定量限制。提出的研究是一种新的、跨学科的构造学方法，利用现代大气建模技术，并将它们应用于地质学中最持久的问题之一，即内华达山脉的表面隆起历史。虽然该方法利用了动力气象学和同位素地球化学技术，但其结果将直接影响我们对北美地质演化的理解。将开发一套用于解释古高程代用记录的新技术，这些技术将在世界各地的广泛环境中使用。一旦在内华达山脉的有限背景下得到证实，这些技术就可以应用于其他地区和时间间隔，以更好地解释隆起历史，并解开古气候记录中混合的海拔/气候信号。这项研究的结果将引起大气科学界的兴趣，因为它将提高我们对几种古气候情景下静态稳定性的认识，并将阐明地形与气候之间的非线性相互作用。因此，这项研究将对固体地球和气候变化社区都具有重要意义。

How long have California's Sierra Nevada Mountains been high? This question is one of the most persistent challenges in unraveling the geological history of North America. Many studies argue that the Sierra Nevada reached high elevation by the Late Cretaceous (about 65 to 100 million years ago) and experienced subsequent limited surface elevation increases. An opposing array of studies argue that the Eocene (about 35 to 55 million years ago) Sierra Nevada had low elevation and weak relief and that a post-Eocene pulse of surface uplift linked to the Pliocene delamination of a crustal root led to the modern elevation of the range. These divergent views embody fundamentally different theories of North American tectonic evolution. The primary sources of evidence for the interpretation that the Sierra Nevada have been a region of persistent high topography since the Eocene are stable isotope and leaf-shape paleoaltimetry techniques. However, a series of recent atmospheric dynamics studies challenge these interpretations. These studies show that current frameworks for interpreting proxy records of precipitation isotopic ratios are based on assumptions about the atmosphere that are not generally valid for the Sierra Nevada or that do not take proper account of paleoclimate variation. The goal of this project is to merge the latest methods from geodynamical studies, atmospheric dynamics, and paleoclimate modeling, to substantially improve interpretations of paleoaltimetric data from the Sierra Nevada and thereby advance understanding of the surface elevation history of the range. The project will rigorously evaluate air parcel trajectories around the Sierra Nevada and associated precipitation isotopic and enthalpy distributions for a range of atmospheric conditions. These will be derived from suites of water-isotope enabled atmospheric General Circulation Model simulations of paleoclimate scenarios from the Eocene through the present, and for a range of proposed topographic settings for western North America over that interval. The result will be improved quantitative constraints on the topography of the Sierra Nevada throughout the Cenozoic and in particular on the potential for Late Cenozoic surface uplift.The proposed study is a new, interdisciplinary approach to tectonics that leverages modern atmospheric modeling techniques and applies them to one of the most persistent problems in geology, the surface uplift history of the Sierra Nevada. While the approach draws on dynamical meteorology and isotope geochemistry techniques, the results will directly impact our understanding of the geological evolution of North America. A suite of new techniques for interpreting paleoaltimetry proxy records that will be of use in a wide range of settings around the world will be developed. Once proven in the limited context of the Sierra Nevada, these techniques can be applied to other regions and time intervals to better interpret uplift histories and disentangle the mixed elevation/climate signals in paleoclimate records. The results of this study will be of interest to the atmospheric sciences community because it will advance our knowledge of static stability in several paleoclimate scenarios and will elucidate the nonlinear interactions between topography and climate. This study will thus have important implications for both the solid earth and climate change communities.