SEASONAL TRENDS OF HYDROGEN AND OXYGEN ISOTOPES IN PRECIPITATION AND LAKE WATER SAMPLES IN CENTRAL NEW YORK: IMPLICATIONS FOR ISOTOPIC PALEOCLIMATE PROXIES

Hydrogen isotope ratios, δ²H, in leaf waxes are used as a proxy to reconstruct past climate because leaf wax δ²H reflects environmental water δ²H-H₂O. The use of compound-specific isotopes as a climate proxy has increased over recent years, however many of the details of the systematics of leaf wax δ²H as a proxy are unknown, indicating further studies are needed to fully understand how climate and leaf wax δ²H relate. One uncertainty about leaf wax δ²H systematics is the seasonality of environmental water that plants use to make leaf waxes, making it difficult to draw conclusions about past climates. As a first step in determining seasonal patterns recorded in sedimentary leaf wax δ²H, we collected environmental water in Central New York and measured year-round δ²H-H₂O and δ¹⁸O-H₂O values. Lake water samples were collected weekly at a small lake. Each week, two water and sediment samples were collected near the surface and two above the lake’s sediment-water interface using sediment traps. Precipitation samples were taken using a system designed to prevent evaporation when a snow or rain event occurred. δ²H and δ¹⁸O of the water molecule were measured on a Picarro L2130-i water isotope analyzer with an instrumental precision of 0.51 ‰ for δ²H-H₂O and 0.08 ‰ for δ¹⁸O-H₂O. We document evidence of seasonal changes of precipitation and lake water δ²H-H₂O and δ¹⁸O-H₂O caused by changing temperature, transport paths, and lake water residence time. Determining seasonal patterns of hydrogen and oxygen isotopes in environmental water samples will allow for comparisons with leaf wax δ²H and determination of the seasonal signalrecorded in sedimentary leaf waxes, which is important for future paleoclimate research.