Collaborative Research: P2C2--Modalities and Time-scale of Climate Variability During the Late Holocene in Southwestern North America

该奖项旨在将美国西南部5,000年前的洞穴沉积物与来自各种环境代理的同位素和化学数据相结合。 这项研究将侧重于影响不同时间尺度上的区域水文循环的气候调节剂。 这些调制因子包括年际变化的厄尔尼诺-南方涛动（ENSO）、十年和多十年的太平洋十年涛动（PDO）和大西洋多十年涛动（AMO）以及可能在不同时间尺度上起作用的太阳变率。选择该地区进行研究是因为它对气候强迫和调节具有良好的水文敏感性。 美国西部有着悠久的气候引发社会混乱的历史，可以追溯到史前。了解这些自然变化将有助于提高对水文循环未来变化的可能预测能力。 这种预测能力将为美国带来社会效益，因为它可以导致更好的资源规划和管理。该项目的另一个好处是得到了一所少数民族大学的一名研究生的支持。来自区域洞穴的洞穴沉积物提供了一个长期观察这些气候调节剂模式可能变化的机会，并证明了它们对同位素的忠实性，化学和物理气候代用指标，利用铀的进步，该项目将专门收集和评估两个具有不同季节水文循环的地点的数据，目的是分离季节性水文循环。观测到的变化的组成部分和负责任的气候变量。例如，北美季风（NAM）受到AMO变化的调制。这种季节性的划分很重要，因为它可以帮助解决NAM和其他最近记录的北方季风之间的一致性变化的难题。

This award generally aims to integrate high-precision age-dated 5,000 year-old speleothems with isotopic and chemical data from various environmental proxies in the southwestern United States. This study will focus on climate modulators that impact regional hydrologic cycles on differing time-scales. These modulators include the inter-annual varying El Nino-Southern Oscillation (ENSO), the decadal and multi-decadal Pacific Decadal Oscillation (PDO) and the Atlantic Multi-Decadal Oscillation (AMO), and solar variability which may act across varied time-scales. This region was chosen for the study because it has well-documented hydrologic sensitivity to climate forcing and modulation. The western United States has a long history of climate induced social disruption, dating back to pre-history. Understanding these natural changes will help contribute to a possible predictive capability of future changes in the hydrologic cycle. Such a predictive capability would be a societal benefit to the United States in that it could result in better resource planning and management. A further benefit of the project is the support of a graduate student at a minority serving university. Speleothems from regional caves provide an opportunity to observe possible changes in the modalities of these climate modulators over the long term and have demonstrated their fidelity to isotopic, chemical and physical climate proxies that are radiometrically datable using advances in uranium-series based chronometry.The project will specifically collect and evaluate data from two sites with different seasonal hydrologic cycles with the aim of isolating the seasonal component of observed changes and the responsible climate variables. For example, the North American Monsoon (NAM) is modulated by changes in the AMO. This seasonal delineation is important because it could help solve the puzzle of the change in coherence between the NAM and other recently documented Northern Hemisphere monsoons.