RPG: Stable Oxygen and Hydrogen Isotope Studies of Groundwater and Wood from the Last Glacial Maximum to the Present

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ABSTRACT EAR-9506752 Feng A commonly used climatic indicator in continental paleoclimatic studies is inferred oxygen and hydrogen isotopic compositions of paleometeoric water either by direct measurements, such as polar ice, or by using proxy indicators, such as lake sediments, soil carbonates, cave deposits, vein calcite, and tree rings. Because climatic indicators are rarely single-variable functions of meteoric water, the climatic reconstructions are not always consistent. In particular, groundwater samples dating back to the Last Glacial Maximum are typically depleted in deuterium relative to worldwide Holocene recharge, while waters inferred from wood cellulose is typically enriched in deuterium. This project attempts to resolve the cause(s) and mechanisms of this observational discrepancy. The main approach is to locate meteoric recharge zones known to be responsible for some of the paleogroundwaters that have been described, and find and analyze wood samples known to have grown in the same area. If the disagreement between Pleistocene groundwater and Pleistocene wood is confirmed, then it may imply fundamental differences in climatic parameters between the Last Glacial Maximum and the Holocene. Emphasis during the Planning Grant will be placed on finding appropriate sites for the study. The focus will be on the north-central and central U.S, where paleogroundwater and ancient wood samples are well documented, and North China, where Pleistocene water is widely distributed. Because the discrepancy between groundwater and wood is a large-scale observation, the causes must be large scale phenomena. Thus, this project should make fundamental contributions to the understanding of the climate and environment.