Collaborative Research: P2C2--Controls on Water Isotope Variability in the Tropical Pacific: A Strategy to Improve Paleoclimate Interpretations

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Paleoclimate reconstructions of past tropical precipitation rely on interpreting hydrogen and oxygen isotopic variations in terms of past changes in precipitation. This project has the goal of better understanding of the response of tropical Pacific precipitation to climatic variability and how the stable isotope composition of the rainfall is affected by seasonal and interannual changes in the climate. The researchers include a scientist and a postdoctoral fellow from Georgia Institute of Technology and a scientist from the University of Colorado. They will collect and measure the stable oxygen and hydrogen isotopes in water vapor, rainfall and seawater from four island locations in the tropical Pacific. Samples will be collected on site during field programs executed by the PIs. The sampling program will also include year-round sampling by local individuals who will be trained in proper sampling techniques. The sampling strategy includes ultra high-resolution sampling of the diurnal cycle, as well as daily and longer sampling in order to evaluate the relationship of water isotope variability to climate change from sub-seasonal to interannual time scales and on a basin wide scale. The stable isotope data will be integrated with an isotope-enabled climate model at the National Center for Atmospheric Research to link the climate mechanisms for the isotope variability at high frequency with the resulting longer term averaged values that typify the type of data reconstructed by paleoclimate proxies of rainfall. Using this approach, the PIs hope to provide a more accurate evaluation of paleoclimate proxies as well as a better understanding of the uncertainties embedded in these types of reconstructions.The recent rise in the number of paleoclimate publications dedicated to measuring and interpreting water stable isotopes, and the possibly oversimplified nature of some of the interpretations, makes this project likely to have a significant impact on paleoclimate research. The project includes two established researchers, Kim Cobb (GA. Tech.) and David Noone (CU), but the main driver of this project is Jessica Conroy, an EAR Postdoctoral Research Fellow at Ga. Tech., supported by the AGS Paleoclimate Program. This project builds on the PRF award by providing greater access to the Pacific for sampling, collaboration with Noone at CU for access to the NCAR GCMs, and a third year of support for the postdoc to complete the work.