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目前拥有的关于过去6000年西方干旱数据的缺陷。目前大多数关于干旱的数据都来自年轮记录，但我们已经意识到，尽管年轮数据提供了很好的年度分辨率，但树木在实际种植年轮时往往只记录夏季天气，而冬季天气没有得到充分代表，因为年轮在这个季节生长缓慢或停止。考虑到冬季降水对西方大部分地区的重要性，数据的这种差距使得精确建模变得困难，这笔赠款将试图通过对湖泊沉积物进行采样来解决这一问题，这些沉积物在底部沉积物中‘记录’全年的天气，尽管其分辨率低于年度分辨率。这项工作将产生一张新的整个研究期间的干旱地图，其中将纳入从西北部不列颠哥伦比亚省到东南部新墨西哥州的地区以前的湖泊和树木年轮记录。赠款将产生六个新的湖泊沉积物记录(两个来自不列颠哥伦比亚省，两个来自艾伯塔省，两个来自新墨西哥州)，这些记录将持续6000年，直到全新世中期，并对闭合盆地湖泊的岩心横断面进行沉积学分析，以限制水位变化，以此作为确认从稳定同位素测量推断的水文变化幅度的物理手段。宾夕法尼亚州立大学的小组将使用华盛顿和不列颠哥伦比亚省之前的努力产生的古变形数据，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)数据同化练习，而PITT和UMN-D小组将从太平洋西北部和西南沙漠的地点产生新的湖平面和稳定的同位素数据，这些数据已经被确定，并在几个案例中取芯。该小组将结合对开阔盆地的同位素记录和叶蜡的测量以及封闭盆地和藻类生物标志物记录的分析，重建不受降水同位素组成变化影响的干旱可变性。该团队已经使用水文和同位素质量平衡模型对湖泊沉积物的氧同位素和湖泊水位记录进行了定量解释，并将合成结果数据以产生一个网格的、古老的网络。这些重建将被用来研究关于中世纪气候异常、小冰河时期和中期全新世期间太平洋西北部和沙漠西南部南北干旱模式的对比假说。该项目将支持实地和实验室的两名研究生以及一些本科生的研究活动，结果将发表在同行评议的期刊上，在专业会议和公开会议上介绍。收集到的岩芯将可供其他研究人员进一步采样，结果将向公众公布，并可在NOAA数据库中获得。

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.