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

了解是什么过程推动了美国西海岸降雨量的变化，对于预测这个人口稠密、农业生产丰富的地区未来的水资源供应至关重要。然而，考虑到直接气象观测的持续时间很短(~100年)，重建过去较长时间段(即数千年)的降雨量变化是有益的，以揭示美国西部水资源对未来气候变化的潜在敏感性。这一研究项目结合了对古地下水的测量和最先进的气候模型实验，以量化和了解美国西海岸在最后一个冰期(即大约25,000年前的最后一次冰期或LGM)期间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部分，包括创建一个博物馆展览，在国家大气研究中心(NCAR)展出。与科罗拉多博尔德大学合作，研究人员将领导一门跨学科的课程，让学生设计并制作博物馆展览的原型，使大冰川风暴期间截然不同的大气环流和降雨模式栩栩如生。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内的水井网络中收集地下水样本的实地活动，这将为数据匮乏的太平洋西北部的大冰盖冰盖水文气候提供亟需的定量约束。将使用一种新的分析技术，高精度测量地下水中溶解的惰性气体浓度和氪、氙同位素比率，以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包括使用NCAR的社区地球系统模式1.2版(CESM1)的气候模式实验，以现有的完全平衡的气候模拟为基础，研究不同的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)的高水分风暴的强度、可变性和登陆方向。该项目还包括一系列模拟去冰川和冰川条件的时间切片实验，以考察ARS和北美西部水气候对大陆冰盖缩小和增长的瞬时响应。最后，将在这些模型模拟和太平洋西北地区地下水位深度的代理重建之间进行详细的比较。这项裁决反映了NSF的法定使命，并通过使用基金会的智力优势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.