Terrestrial and aquatic leaf wax hydrogen isotope proxy system models: Recent advances and remaining gaps

Constraining the hydrological response to past climate change can improve climate model predictions. These constraints are most useful when provided in variables that are native to climate models (e.g., precipitation or soil water isotope values during a defined season). Leaf wax hydrogen isotopes extracted from lake sediments are valuable proxies to reconstruct the hydrological cycle. In some lakes, multiple leaf wax compounds may provide information about different aspects of the climate system (e.g., precipitation isotope seasonality, growing season evaporation, etc.), increasing the amount of information we obtain from a single measurement. Yet, the pathway by which climate signals are recorded in leaf wax hydrogen isotopes can be complex, as the isotope signal is filtered through the environment (lake or soil water) and the sensor (integrating waxes from aquatic plants and from terrestrial plants throughout the lake’s catchment). This presentation will summarize our recent and ongoing research examining how climate signals are filtered through both the environment and sensor, with the goal of providing reconstructions in terms native to isotope-enabled climate models. We will highlight studies examining lake water isotope systematics and leaf wax sources to lake sediments, emphasizing aspects of these frameworks that are applicable to other stable water isotope proxies. We will also discuss outstanding questions and avenues for future research.