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

该奖项一般旨在将高精度的5000年前的洞穴化石与来自美国西南部各种环境代理的同位素和化学数据结合起来。本研究将侧重于在不同时间尺度上影响区域水文循环的气候调节剂。这些调制器包括年际变化的厄尔尼诺-南方涛动（ENSO）、年代际和多年代际的太平洋年代际涛动（PDO）和大西洋多年代际涛动（AMO），以及可能在不同时间尺度上起作用的太阳变率。之所以选择该地区进行研究，是因为该地区的水文对气候强迫和调节具有充分的敏感性。早在史前时期，美国西部就有气候导致社会混乱的悠久历史。了解这些自然变化将有助于提高对未来水文循环变化的预测能力。这种预测能力对美国来说将是一种社会效益，因为它可能导致更好的资源规划和管理。该项目的另一个好处是得到少数民族大学研究生的支持。区域洞穴的洞穴化石提供了一个机会，可以观察这些气候调节剂的模式在长期内可能发生的变化，并证明了它们对同位素、化学和物理气候代用品的忠实性，这些代用品可以利用基于铀系的时代学技术的进展在放射性上获得数据。该项目将具体收集和评估两个具有不同季节水文循环的地点的数据，目的是分离观测到的变化的季节成分和负责任的气候变量。例如，北美季风（NAM）是由AMO的变化调制的。这种季节性描述很重要，因为它可以帮助解决不结盟运动与最近记录的其他北半球季风之间一致性变化的难题。

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.