RECONSTRUCTING ARCTIC HYDROLOGY USING THE HYDROGEN ISOTOPIC COMPOSITION OF LEAF WAXES

The Pliocene epoch (5-2.65 Ma) represents an analog for future climate conditions, with atmospheric carbon dioxide concentrations and continental configurations similar to present. Thus, understanding the climatic changes that occurred during the Pliocene might be useful for predicting how climate will evolve in the future. One proxy increasingly applied to reconstruct climatic conditions from Arctic sediments is the hydrogen isotopic composition of leaf waxes (δD_wax). Although δD_wax records are a powerful tool for understanding past changes, they can be difficult to interpret because changes in temperature, moisture source region, precipitation amount, and biosynthetic fractionation all influence δD_wax. Here we present a Pliocene record of δD_wax from Lake El’gygytgyn, Arctic Northeast Russia, and use independent proxies for past temperature (brGDGTs) and vegetation (pollen) to isolate changes in δD_wax due to moisture source region and precipitation amount. We then perform the same analysis on a new record from the same site covering the Eemian (~125,000 years ago (ka)) and the Holocene (the last 10 ka) epochs, for which climatic boundary conditions are much better constrained. Our analysis reveals how Arctic hydrology changed between the Holocene and two past warm periods, the Eemian and the Pliocene, which can inform efforts to predict future changes in the Arctic under continued global warming.