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

该奖项的主要目的是将高精度的5000年前的洞穴化石与美国西南部各种环境指标的同位素和化学数据结合起来。这项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器。这些调制器包括年际变化的厄尔尼诺-南方涛动(ENSO)、年代际和年代际太平洋年代际涛动(PDO)和大西洋多年代际涛动(AMO)，以及可能在不同时间尺度上作用的太阳变率。之所以选择这一地区进行研究，是因为它对气候强迫和调制的水文敏感性有据可查。美国西部的气候引起的社会混乱有着悠久的历史，可以追溯到史前。了解这些自然变化将有助于对未来水文循环变化的可能预测能力。这种预测能力将给美国带来社会效益，因为它可以带来更好的资源规划和管理。该项目的另一个好处是支持少数族裔服务大学的一名研究生。来自区域洞穴的洞穴洞穴提供了一个机会，可以长期观察这些气候调节器模式的可能变化，并证明了它们对同位素、化学和物理气候指标的保真度，这些指标可以利用基于铀系列的计时技术的进步进行辐射测量。该项目将专门收集和评估来自两个具有不同季节性水文循环的地点的数据，目的是分离出观测到的变化的季节性成分和负责的气候变量。例如，北美季风(NAM)受AMO变化的影响。这种季节划分很重要，因为它可以帮助解决北半球季风和最近记录的其他北半球季风之间的一致性变化的谜题。

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.