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

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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.