Collaborative Research: Regional hydrologic and vegetation changes over the last 150 kyr in the Searles and Death Valley basins

美国西南部目前正经历着严重的水资源压力，预计在下个世纪将面临可用水资源的减少。该地区过去的水丰度变化可以通过对古湖盆的研究来记录。该项目将重建美国西南部塞尔盆地和死亡谷盆地过去15万年的可用水资源、植被和水分来源。研究人员将利用每个盆地的海岸线沉积物来限制古代湖泊的水位。来自每个盆地中心的沉积物岩心记录将提供跨越湿期和干期的古气候信息。保存在岩心中的植物蜡将提供对过去反映水分来源变化的植被变化的深入了解。沉积物的放射性定年法将给出古湖泊环境变化的精确年代。湖泊岸线年龄将用于解释塞尔斯和死亡谷盆地过去的湖泊容量。总的来说，这些信息将用于模拟过去的河流流量和水预算。这项工作还将为塞尔盆地320万年的连续沉积物记录的未来发展奠定基础，包括过去的温暖时期。该项目将在5所院校培养研究生和本科生。宾厄姆顿大学的参与者将通过与死亡谷自然历史协会的合作，带领游客到死亡谷国家公园进行实地考察。南加州大学的外展活动将包括与拉布雷亚沥青坑博物馆的合作，重点是向四年级的游客介绍更新世湖泊与博物馆中同一时代的化石动物群之间的关系。麻省理工学院的研究小组将在剑桥科学节、麻省理工学院博物馆的女生节和新英格兰水族馆将项目结果纳入气候主题的宣传活动中。来自纽约州立大学奥斯威戈分校和基斯顿学院的研究人员将把研究成果纳入每年面向数百名学生的古气候和可持续性课程。美国西南部是一个水资源紧张的地区，预计在未来一个世纪，可用水资源将不断减少。模式预估显示，区域环流对预估排放情景的响应存在很大差异，对未来干旱的幅度和空间特征的预测存在分歧。湖泊记录有可能提供水文、大气和植被对各种强迫响应的详细重建，并为未来的基准模型性能提供机会。南加州塞尔斯和死亡谷流域的湖泊记录显示，在过去150年里，湖泊水位和植被发生了巨大变化，这在一定程度上反映了具有重要社会意义的欧文斯河系统的河流流量发生了巨大变化。这些记录需要新的分析来改进不精确的年表，并改进湖泊水位重建和邻近盆地的相关性。该项目是对Searles和死亡谷盆地过去150年来的水文和植被变化的多方面重建。研究人员将使用凝灰岩和其他近岸沉积物来限制两个盆地的湖泊水位，并使用最近收集的岩心（Searles盆地的slap - srls17岩心和死亡谷的DV93-1岩心）的现有和新的测量数据来提供连续的多代理记录。沉积结构和结构、蒸发岩矿物学和相、硅屑粒度变化和岩心岩石磁性变化将与海岸线约束一起用于模拟Searles盆地过去的水文和湖泊化学变化，为过去的河流流入和降水-蒸发平衡提供定量约束。植物蜡δ 13c和花粉将提供对过去植被变化的洞察，植物蜡δ将用于跟踪水分来源和水蒸气历史的变化。在Searles湖沉积物的14C和古地磁测量的支持下，两个盆地的U/Th定年将用于提供精确的年龄模型。古强度变异性和磁场漂移证据将为SLAPP-SRLS17岩心定年提供一种独立的方法。这两个盆地将共同提供复制的、年代准确的水文和植被记录，使用独立的方法来测试对东北附近魔鬼洞和利维坦洞穴的洞穴氧同位素记录的解释。这些记录将提供储水量变化和降水同位素变化幅度的定量估计，以更好地确定大气环流变化及其产生的水文影响。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。

The southwestern U.S. is currently experiencing profound water stress and is predicted to face declining water availability in the coming century. Past variations in the abundance of water in this region can be documented from study of ancient lake basins there. This project will produce a reconstruction of water availability, vegetation, and moisture sources in the Searles and Death Valley basins of the southwestern U.S. spanning the last 150,000 years. The researchers will use shoreline deposits from each basin to constrain ancient lake levels. Sediment core records from the centers of each basin will provide paleoclimate information that spans both wet and dry periods. Plant wax preserved in the cores will provide insight into past vegetation changes that reflect variations in moisture sources. Radiometric dating of sediments will give precise ages of environmental changes in the ancient lakes. Lake shoreline ages will be used to interpret past lake volumes in the Searles and Death Valley basins. Collectively, this information will be used to model past river flow and water budgets. This work will also lay the foundation for future development of a continuous 3.2 million-year sediment record from the Searles basin, including past warm periods. This project will train graduate and undergraduate students at 5 institutions. Binghamton University participants will lead field tours to visitors to Death Valley National Park through a partnership with the Death Valley Natural History Association. Outreach at the University of Southern California will involve collaboration with the La Brea Tar Pits Museum and will focus on teaching 4th grade visitors how Pleistocene lakes relate to the museum fossil fauna of the same age. The MIT group will incorporate project findings into climate-themed outreach at the Cambridge Science Festival, Girls' Day at the MIT Museum, and at the New England Aquarium. Researchers from SUNY College at Oswego and Keystone College will incorporate research outcomes into paleoclimate and sustainability courses that reach hundreds of students per year.The southwestern U.S. is a water-stressed region that is projected to experience declining water availability over the coming century. Model projections show substantial disagreement in the regional circulation responses to projected emissions scenarios, with divergent predictions of the magnitude and spatial fingerprint of future drying. Lake records have the potential to offer detailed reconstructions of the hydrological, atmospheric, and vegetation responses to a wide range of forcings and to provide future opportunities to benchmark model performance. Lake records from the Searles and Death Valley basins in southern California show dramatic lake level and vegetation changes over the last 150 kyr, reflecting in part large changes in river flow from the societally-important Owens River system. These records require new analyses to improve imprecise chronologies and refine lake level reconstructions and correlations from these neighboring basins. This project is a multi-faceted reconstruction of past hydrologic and vegetation changes spanning the last 150 kyr in the Searles and Death Valley basins. The researchers will use tufa and other nearshore deposits to constrain lake levels in both basins, and existing and new measurements from a recently collected core, SLAPP-SRLS17 from Searles basin, and core DV93-1, Death Valley, to provide continuous multi-proxy records. Sedimentary structures and textures, evaporite mineralogy and facies, siliciclastic grain size changes, and rock magnetic variations in cores will be used with shoreline constraints to model past hydrologic and lake chemistry changes in Searles basin, providing quantitative constraints on past river inflows and precipitation-evaporation balance. Plant wax delta13C and pollen will provide insight into past vegetation changes, and plant wax deltaD will be used to track changes in moisture source and water vapor history. In both basins, U/Th dating will be used to provide precise age models, with support from 14C and paleomagnetic measurements in Searles Lake deposits. Paleointensity variability and evidence for magnetic field excursions will provide an independent method for dating the SLAPP-SRLS17 core. Together, the two basins will provide replicated, well-dated hydrological and vegetation records using independent approaches to test interpretations of the cave oxygen isotope records from nearby Devils Hole and Leviathan Caves to the northeast. These records will provide a quantitative estimate of the volumetric changes in water storage and the magnitude of precipitation isotopic shifts to better determine atmospheric circulation changes and the resulting hydrologic implications.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.