Collaborative Research: Spatial and Temporal Patterns of Drought in Western North America during the Holocene

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。该拨款产生的古气候数据集记录的时间，持续时间，频率和干旱周期的大小对开放和封闭泥晶盆地网络沿着北美西部科迪勒拉从太平洋西北部到加拿大北极。该项目采用水文和稳定同位素质量平衡模型，提供降水和相对湿度变化的定量估计。该项目探讨了全新世期间干旱的时间地理模式如何变化，并使用先进的数据处理技术来测试有关古气候档案中周期性的假设。这些结果被用来推断太平洋变化的潜在模式的性质，并记录它们如何随着时间的推移而变化。该项目检验关于全新世期间研究区域气候变化的原因和幅度的假设。该项目还综合了来自文献的数据，并正在热带南美洲开展工作，以调查一系列时间尺度上的大规模太平洋强迫。这些记录的综合将使人们更好地了解太平洋气候系统，并提高北美西部干旱周期的可预测性。湖泊水平沿着西部科迪勒拉一直相对稳定，在过去的6 ka创建高分辨率的档案，在这段时间内针对最激烈的研究。在全新世早期，特大干旱显著降低了区域水位，从而限制了分辨率，以几十年到世纪尺度前~ 6 ka。137 Cs、210 Pb、14 C、火山灰年代学和地磁对比提供了年代学资料。在所有研究中心采用相同的方法，以简化数据解释并增加结果的稳健性。多重代用研究将包括稳定同位素、灰度、漫反射光谱、X射线荧光、磁性测量以及烧失量测定的有机和无机碳。该研究小组与不列颠哥伦比亚省大学合作，利用摇蚊组合来重建古温度。多千年的水文记录与子十年分辨率进行比较，高分辨率耦合海洋大气GCM模拟目前正在进行的合作者在普渡大学。这项工作是有关北美西部的人口迅速扩大和水资源的压力。相对稀疏的preinstrumental气候记录，这一地区表明，它是高度敏感的太平洋变率和PDO和AMO之间的相互作用。为了提高预测能力，需要更深入地了解这些变异模式的过去行为。其目标是以与人类社会相关的时间分辨率调查气候变化，并回答以下问题：全新世期间干旱和多雨的强度和周期性如何变化？这一时期北美西部干旱循环的空间格局是什么？什么样的边界条件和强迫因素与极端干旱和暴雨有关？

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).This grant produces paleoclimate datasets recording the timing, duration, frequency and magnitude of aridity cycles on a network of paired open and closed micritic basins along the western cordillera of North America from the Pacific NW to the Canadian Arctic. The project employs hydrologic and stable isotope mass balance models to provide quantitative estimates of precipitation and relative humidity changes. The project explores how the temporal-geographic patterns of aridity changed during the Holocene and uses advanced data processing techniques to test hypotheses concerning the periodicities in the paleoclimate archives. These results are used to infer the nature of potential modes of Pacific Ocean variability and to document how they have changed over time. The project tests hypotheses concerning the causes and magnitude of climate variability in the study region during the Holocene. The project also synthesizes data from the literature with ongoing work in Tropical South America to investigate large-scale Pacific Ocean forcing over a range of timescales. Synthesis of these records will result in a better understanding of the Pacific climate system and improved predictability for aridity cycles in western North America. Lake levels along the western cordillera have been relatively stable during the past ~6ka creating high resolution archives during the period of time targeted for most intense study. During the early Holocene megadroughts significantly lowered water levels regionally thereby limiting the resolution to multi-decadal to century scale prior ~6ka. Geochronology is provided by 137Cs, 210Pb, 14C, tephra chronology and geomagnetic correlation. The same methods are applied at all study sites to simplify data interpretation and increase robustness of findings. Multiproxy studies will include stable isotopes, grayscale, diffuse spectral reflectance, XRF, magnetic measurements, and organic and inorganic carbon by loss on ignition. The group collaborates with the University of British Columbia, who use chironomid assemblages to reconstruct paleotemperatures. The multi-millennial hydrologic record with sub-decadal resolution is then compared with high resolution coupled ocean atmosphere GCM simulations currently being conducted by a collaborator at Purdue University.The work is relevant to western North America where populations are rapidly expanding and water resources are stressed. The relatively sparse preinstrumental climate records for this region indicate that it is highly sensitive to Pacific Ocean variability and to the interaction between the PDO and AMO. A deeper understanding of the past behavior of these modes of variability is needed to improve predictive capabilities. The goal is to investigate climatic change at a time-resolution relevant to human society, and answer questions such as: How have the intensity and periodicity of droughts and pluvials changed during the Holocene? What is the spatial pattern of aridity cycles in western North America during this period? What boundary conditions and forcing factors are related to extreme droughts and pluvials?