Collaborative Research: An integrated model-proxy approach to understanding Western US hydroclimate change since the last glacial period

了解是什么过程导致了美国西海岸降雨的变化，对于预测这个国家人口密集和农业生产地区未来的水资源供应至关重要。然而，由于直接气象观测的持续时间较短（~100年），为了揭示美国西部水资源对未来气候变化的潜在敏感性，重建较长时间（即数千年）的过去降雨变化是有益的。该研究项目结合了古代地下水测量和最先进的气候模型实验，以量化和理解末次冰期（即末次盛冰期，约25,000年前）美国西海岸水文变化的动力驱动因素。该项目还包括一个全面的公共宣传组成部分，包括在国家大气研究中心（NCAR）建立一个博物馆展览。在与科罗拉多大学博尔德分校的合作中，研究人员将领导一门跨学科课程，让学生设计和制作一个博物馆展览的原型，使LGM期间出现的完全不同的大气环流和降雨模式变得生动。该项目的第一个研究部分包括从俄勒冈州东北部和华盛顿州东南部哥伦比亚高原含水层系统的水井网络中收集地下水样本的实地活动，这将为数据贫乏的太平洋西北部的LGM水文气候提供急需的定量约束。一种新的高精度测量地下水中溶解惰性气体浓度和氪氙同位素比值的分析技术将用于重建过去的温度和区域地下水位深度。该项目的第二个研究部分涉及气候模式实验，使用NCAR的社区地球系统模型1.2版（CESM1），以现有的完全平衡气候模拟为基础，研究不同LGM边界条件（冰盖反照率/地形、温室气体、轨道强迫等）对北太平洋大气环流的影响，以及被称为大气河流（ARs）的富湿风暴的强度、变异和登陆方向。该项目还包括一系列时间切片实验，模拟冰川消融和冰川条件，以检查ARs和北美西部水文气候对大陆冰盖萎缩和增长的瞬态响应。最后，将这些模型模拟结果与太平洋西北地区地下水位的替代重建结果进行了详细的比较。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Understanding what processes drive changes in rainfall along the U.S. West Coast is essential for predicting future water availability in this densely populated and agriculturally productive part of the country. However, given the short duration of direct meteorological observations (~100 years), it is beneficial to reconstruct past changes in rainfall over longer time periods (i.e., thousands of years) in order to uncover the potential sensitivity of water resources in the Western U.S to future climate change. This research project combines measurements of ancient groundwater and state-of-the-art climate model experiments to both quantify and understand the dynamical drivers of hydrological change along the American West Coast during the last ice age (i.e., the Last Glacial Maximum or LGM, ~25,000 years ago). This project also includes a comprehensive public outreach component, involving the creation of a museum exhibit for display at the National Center for Atmospheric Research (NCAR). In collaboration with the University of Colorado Boulder, the researchers will lead an interdisciplinary course for students to design and prototype a museum exhibit that brings to life the radically different atmospheric circulation and rainfall patterns present during the LGM.The first research component of this project involves a field campaign to collect groundwater samples from a network of wells within the Columbia Plateau Aquifer system in northeastern Oregon and southeastern Washington, which will provide a much-needed quantitative constraint on LGM hydroclimate in the data-poor Pacific Northwest. A new analytical technique for high-precision measurements of dissolved noble gas concentrations and Krypton and Xenon isotope ratios within the groundwater will be employed to reconstruct past temperature and regional water table depth. The second research component of the project involves climate model experiments using NCAR’s Community Earth System Model version 1.2 (CESM1) to build upon existing fully equilibrated climate simulations to study the influence of different LGM boundary conditions (ice sheet albedo/topography, greenhouse gases, orbital forcing, etc) on North Pacific atmospheric circulation and the intensity, variability, and landfalling orientation of moisture-rich storms known as Atmospheric Rivers (ARs). The project also includes a series of time-slice experiments, simulating both deglacial and glacial conditions, to examine the transient response of ARs and western North American hydroclimate to shrinking and growing continental ice sheets. Finally, detailed comparisons will be made between these model simulations and the proxy reconstructions of Pacific Northwest water table depths.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.