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，预计下个世纪将面临水资源供应下降的局面。通过对该地区古代湖盆的研究，可以证明该地区过去水丰度的变化。该项目将重建美国西南部瑟尔斯盆地和死亡谷盆地过去15万年的水资源供应、植被和湿润来源。研究人员将利用每个盆地的海岸线沉积来限制古代湖泊的水位。来自每个盆地中心的沉积岩心记录将提供跨越丰水期和枯水期的古气候信息。保存在岩芯中的植物蜡将提供对反映水分来源变化的过去植被变化的洞察。对沉积物的放射性测年将给出古代湖泊环境变化的准确年龄。湖泊海岸线年龄将被用来解释塞尔斯群岛和死亡谷盆地过去的湖泊体积。总而言之，这些信息将被用来模拟过去的河流流量和水收支。这项工作还将为未来从塞尔斯盆地连续记录320万年的沉积物奠定基础，包括过去的暖期。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，带领游客参观死亡谷国家公园。南加州大学的外联活动将涉及与La Brea Tar Pits博物馆的合作，并将重点教授四年级游客更新世湖泊与同一时代博物馆化石动物群的关系。麻省理工学院的团队将在剑桥科学节、麻省理工学院博物馆的女生节和新英格兰水族馆的气候主题推广活动中纳入项目成果。纽约州立大学奥斯威戈分校和Keystone学院的研究人员将把研究成果纳入古气候和可持续发展课程，每年有数百名学生参加。美国西南部是一个水资源紧张的地区，预计下个世纪水资源将减少。模型预测显示，区域环流对预测排放情景的反应存在很大差异，对未来干燥的规模和空间指纹的预测存在分歧。湖泊记录有可能提供对各种强迫的水文、大气和植被响应的详细重建，并提供未来对模型性能进行基准测试的机会。加利福尼亚州南部瑟尔斯和死亡谷盆地的湖泊记录显示，在过去150 KYR期间，湖泊水位和植被发生了戏剧性的变化，部分反映了具有社会重要性的欧文斯河系河流流量的巨大变化。这些记录需要新的分析，以改进不精确的年代学，并完善湖平面重建和来自这些邻近盆地的对比。这个项目是一个多方面的重建过去水文和植被的变化，跨越过去150 KYR在瑟尔斯盆地和死亡谷盆地。研究人员将利用凝灰岩和其他近岸沉积物来限制这两个盆地的湖泊水位，并从最近从瑟尔斯盆地收集的SLAPP-SRLS17岩芯和死亡谷DV93-1岩心进行现有和新的测量，以提供连续的多代理记录。沉积构造和结构、蒸发岩矿物学和相、岩心硅质碎屑粒度变化和岩石磁性变化将与海岸线约束一起用于模拟瑟尔斯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Delta13C和花粉将提供对过去植被变化的洞察，植物蜡DeltaD将用于跟踪水分来源和水汽历史的变化。在这两个盆地，U/Th测年将被用来提供精确的年龄模型，并得到赛尔勒斯湖沉积物的14C和古地磁测量的支持。古强度的变化和磁场漂移的证据将为SLAPP-SRLS17岩心提供一种独立的测年方法。这两个盆地将共同提供重复的、日期准确的水文和植被记录，使用独立的方法来测试附近魔鬼洞和东北部利维坦洞穴的洞穴氧同位素记录的解释。这些记录将对水储存的体积变化和降水同位素位移的大小提供定量估计，以更好地确定大气环流变化和由此产生的水文影响。该奖项反映了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。

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.