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

这项合作赠款将有助于解决我们在过去6,000年中西部干旱数据的不足。目前，大多数干旱数据来自树木年轮记录，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，但树木往往只记录夏季天气，而实际上它们正在生长年轮，冬季天气代表性不足，因为年轮生长缓慢或在这个季节停止。鉴于冬季降水对西部大部分地区的重要性，这种数据差距使得准确建模变得困难，这笔拨款将试图通过对湖泊沉积物进行采样来解决这个问题，湖泊沉积物在其底部沉积物中“记录”全年的天气，尽管低于年度分辨率。这项工作将产生一个新的干旱地图，在整个研究期间，将纳入以前的湖泊和树木年轮记录，从西北部的不列颠哥伦比亚省到东南部的新墨西哥州。赠款将产生六个新的湖泊沉积物记录（两名来自不列颠哥伦比亚省，两个来自阿尔伯塔，两个来自新墨西哥州），这将延续6000年，通过中全新世，并进行沉积学分析的核心断面，从封闭的-因此，我们需要对流域湖泊进行监测，以限制水位变化，作为确认从稳定同位素测量推断的水文变化幅度的一种物理手段。宾夕法尼亚州立大学的研究小组将使用先前在华盛顿和不列颠哥伦比亚省的研究中获得的古生物数据，以及已发表的研究数据，以改进中等复杂性地球系统模型（EMIC）的数据同化工作，而皮特和UMN-D研究小组将从太平洋西北部和沙漠西南部已经确定并在某些情况下取芯的地点产生新的湖泊水平和稳定同位素数据。该小组将把开放盆地同位素记录和叶蜡氘测量的联合收割机分析与封闭盆地和藻类生物标志物记录结合起来，以重建不受降水同位素组成变化影响的干旱变化。该小组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，以生成一个网格化的古网络。这些重建将用于调查中世纪气候异常、小冰期和全新世中期太平洋西北部和沙漠西南部对比南北干旱模式的假设。该项目将支持两名研究生在野外和实验室以及一些本科生研究活动，结果将发表在同行评议的期刊上，在专业会议和公共会议上发表。收集的岩心将可供其他研究人员进一步取样，结果将在NOAA数据库中公开提供。

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.