Doctoral Dissertation Research: An Evaluation of Sedimentary Lipid Hydrogen Isotopes as an Arctic Precipitation Proxy

Northwestern University, Evanston IL

Investigators

Abstract

This doctoral dissertation research project will characterize the distribution and hydrogen isotopic composition of plant biomarkers in lake sediments and modern plants to reconstruct past hydroclimate environments in the Arctic. By inferring the isotopic composition of past precipitation patterns and lake waters, this research will facilitate better modeling of the impacts of environmental change on Arctic ecosystems. Improved reconstruction of past hydroclimates will provide a more comprehensive understanding of the Arctic's atmospheric circulation responses to amplified thermal configurations. The project promises a significant STEM education component led by three early-career women that includes the engagement of several undergraduate students in research activities. In addition, the doctoral student will work with the PI on workshops for K-12 STEM teachers from Chicago and Evanston public schools to incorporate current scientific information into their educational materials. As a Doctoral Dissertation Research Improvement award, this award will provide support to enable a promising student to establish a strong independent research career. Existing paleoclimate records provide unique perspectives on how climate related to the hydrologic cycle varied temporally over the Arctic. However, there presently are insufficient data samples and inadequately calibrated proxies to confidently assess changes in hydroclimate. To facilitate improved reconstructions of past hydroclimate environments, the doctoral student will develop new methodologies for characterizing the distributions and hydrogen isotopic values of modern lipids in lake sediments and modern plants along an extensive latitudinal and climatic transect. Gas chromatography and mass spectrometry will be used on lake sediments cores to derive a dataset of plant biomarkers and their correlates (alkanes and acids.) Sedimentary leaf wax and aquatic plant lipid hydrogen isotopes will be measured and used to infer source water hydrogen isotopes by applying a fractionation correction. By answering fundamental questions about the characterization of lipid biomarkers and the relationship between lipid biomarkers and source water, the research will advance the broader application of using hydrogen lipid biomarkers as a paleohydrologic proxy in sedimentary archives.