The School of Earth and Atmospheric Sciences Presents Dr. Magdalena "Maggie" Osburn, Northwestern University

Leaf Waxes and Paleoclimate: What Plant Lipids Can (and cannot) Tell Us About the Climate History of Greenland?

Geological records of past climate provide invaluable constraints on models of future climate trajectories, but are dependent on robust proxies with which to infer climate parameters from long ago. A key proxy in the reconstruction of past hydroclimate is leaf wax molecular paleohydrology. Here, the hydrogen isotopic composition of organic biomarkers derived from plants are used to estimate the isotopic composition of plant source water and by inference, paleo rainwater, lake water, and humidity. 

While this tool has been applied widely and successfully at low latitudes, application to Arctic environments requires reevaluation of fundamental assumptions inherent to this proxy. Here I will describe our work to evaluate these assumptions, including the sources of biomarkers to the sedimentary record and their differences from environmental waters, first at a single watershed scale and then across all of Greenland. By constraining what we can and cannot say with these methods we are then able to evaluate our geological records with more confidence. 

I will discuss lake sediment records capturing the Holocene and Eemian, comparing these two warm periods in the context of molecular paleohydrology and refined temperature estimates. Together, this work serves to strengthen the application this proxy to Arctic environments, constraining how this sensitive environment has responded during past warm periods, and ultimately informing our warming future.