P2C2: Collaborative Research: Quantitative Reconstruction of Past Drought Patterns in Western North America Using Lakes, Stable Isotopes, and Modeling

这一合作赠款将有助于解决目前西部地区过去6000年干旱数据的不足。目前，大多数关于干旱的数据都来自树木年轮记录，但我们已经意识到，尽管树木年轮数据提供了很好的年度分辨率，但树木在实际生长年轮时往往只记录夏季天气，而冬季天气的代表性不足，因为在这个季节，年轮生长缓慢或停止。考虑到冬季降水对西部大部分地区的重要性，数据上的差距使得精确建模变得困难，这笔拨款将试图通过采样湖泊沉积物来解决这一问题，这些沉积物在其底部沉积物中“记录”了全年的天气，尽管低于年分辨率。这项工作将产生一幅贯穿整个研究期间的新的干旱地图，该地图将结合从西北的不列颠哥伦比亚省到东南部的新墨西哥州的以前的湖泊和树木年轮记录。这笔拨款将产生6个新的湖泊沉积物记录（2个来自不列颠哥伦比亚省，2个来自阿尔伯塔省，2个来自新墨西哥州），这些记录将延续6000年，贯穿全新世中期，并对封闭盆地湖泊的核心样带进行沉积学分析，以约束水位变化，作为确认从稳定同位素测量推断出的水文变化幅度的物理手段。宾夕法尼亚州立大学的研究小组将使用以前在华盛顿和不列颠哥伦比亚省获得的古干旱数据，以及发表的研究数据，以改进中等复杂性地球系统模型（EMIC）数据同化练习，而皮特大学和UMN-D大学的研究小组将从太平洋西北部和西南沙漠的地点获得新的湖泊水位和稳定同位素数据，这些数据已经被确定并在一些情况下进行了核心。该小组将把对开放盆地同位素记录和叶蜡氘测量的分析与封闭盆地和藻类生物标志物记录结合起来，重建不受降水同位素组成变化影响的干旱变异性。该团队利用水文和同位素质量平衡模型对湖泊沉积物氧同位素和湖泊水位记录进行了定量解释，并将综合所得数据，生成网格化的古干旱网络。这些重建将用于研究中世纪气候异常、小冰河期和全新世中期太平洋西北地区和沙漠西南地区南北干旱模式的对比假设。该项目将支持两名实地和实验室的研究生，以及一些本科生的研究活动，研究结果将发表在同行评审的期刊上，并在专业会议和公开会议上发表。收集到的岩心将供其他研究人员进一步采样，结果将在NOAA数据库中公开获取。

This collaborative grant will help address current shortcomings of the data we have on Western droughts during the last 6,000 years. Currently most data on droughts has been derived from tree-ring records, but we have realized that although tree-ring data give excellent annual resolution, trees tend to record only summer weather while they are actually growing the ring, and winter weather is under-represented because ring growth is slow or stopped during this season. Given the importance of winter precipitation for much of the West, this gap in data has made accurate modeling difficult, and this grant will attempt to address that by sampling lake sediments, which 'record' the weather throughout the year in their bottom sediments, although at less than annual resolution. This work will result in a new map of droughts throughout the study period that will incorporate previous lake and tree-ring records from a region spanning from British Columbia in the Northwest to New Mexico in the Southeast.The grant will produce six new lacustrine sediment records (two from British Columbia, two from Alberta and two from New Mexico) that would extend 6000 years through the middle Holocene and conduct sedimentological analyses on core transects from closed-basin lakes to constrain water-level changes as a physical means of confirming the magnitude of hydrologic change inferred from the stable isotope measurements. The Penn State group will use paleodrought data produced previous efforts in Washington and British Columbia, as well as data from published research to improve intermediate complexity Earth system model (EMIC) data assimilation exercises, while the Pitt and UMN-D groups will produce new lake-level and stable isotope data from sites in the Pacific northwest and the desert southwest that have already been identified and in several cases cored. The team would combine analyses of open-basin isotope records and leaf wax deuterium measurements with the closed-basin and algal biomarker records to produce reconstructions of drought variability that are not influenced by changes in the isotopic composition of precipitation. The team has quantitatively interpreted the lake sediment oxygen isotope and lake level records using hydrologic and isotope mass balance models, and will synthesize the resulting data to produce a gridded, paleodrought network. These reconstructions would be used to investigate hypotheses regarding contrasting, North-South drought patterns in the Pacific Northwest and the desert Southwest during the Medieval Climate Anomaly, the Little Ice Age and middle Holocene.The project will support two graduate students in the field and laboratory, as well as some undergraduate research activities, and the results will be published in peer-reviewed journals, presented at professional conferences and public meetings. The collected cores will be available for further sampling by other researchers, and the results will be made publicly accessible and available in a NOAA database.