MODERN CALCITE PRODUCTION IN SENECA LAKE, NY

The oxygen isotopic composition of lacustrine carbonates is used often to reconstruct past temperature. Few studies document a relationship between the oxygen isotopic composition of lake water, the oxygen isotopic composition of calcite and temperature for the modern lake prior to interpretation of changes in δ¹⁸O of calcite preserved in the stratigraphic record. Previous sediment trap studies suggest that the δ¹⁸O of calcite is a reasonable proxy for the annual temperature and the δ¹⁸O of lake water.

In this study, we deployed an automated sediment trap in the hypolimnion of Seneca Lake, a large (lake surface area = 175.4 km²), monomictic, glacial, hardwater lake located in wstern New York. Sediment trap material collected every 3-7 days between May 2009 and March 2011 together with isotopic monitoring of surface and bottom water allow for analysis of the controls on calcite precipitation in the lake. We show that calcite mainly accumulates in traps July through September when the lake water column is stratified and epilimnetic water temperature exceeds 20°C. Up to ~70% of the sediment is comprised of calcite during summer and only ~10% of the sediment is calcite during autumn, winter, and spring. Our temperature reconstruction using the δ¹⁸O of calcite and epilimnetic lake water reveals that calcite was a reasonable proxy for temperature from July through September. During the remainder of the year, reconstructed temperatures exceed actual temperatures by as much as 16°C. Sediment resuspension (including calcite) during isothermal conditions may explain why calcite is a poor predictor of lake surface temperature in late autumn though spring. The δ¹⁸O of calcite in this lake likely records summer temperatures rather than year-round conditions.