LATE HOLOCENE CLIMATE RECONSTRUCTION USING STABLE ISOTOPES IN A SPELEOTHEM FROM GAGE CAVERNS, NEW YORK

With future climate change as a result of increased atmospheric CO₂ concentrations uncertain, a strong need exists for precisely-dated, high-resolution regional climate records of the Holocene epoch. Systematic knowledge of the climate of this time period will aid in the understanding of natural climate variability in the absence of anthropogenic pressures. The late Holocene climate has been somewhat variable, with several climate cycles, several of which are thought to be regional in nature, including the Neoglacial (3300-2500 B.P.), Roman Warm Period (2500-1600 B.P.), Medieval Warm Period (950-1250 A.D.), and the Little Ice Age (1350-1850 A.D.). The focus of this study concentrates on paleo-climate conditions 4200 years B.P. to the present in central New York State, a region largely lacking well-dated climate proxies. Oxygen and carbon isotope (δ¹⁸O and δ¹³C) analysis of a speleothem (GS-1) from Gage Caverns, New York, is expected to produce data that will reflect mean annual temperature, rainfall variability, and vegetation response in the region. U/Th dating shows the speleothem started growing ~4200 years B.P. with a steady growth rate of 0.8 ± 0.1 cm per century with no obvious hiatuses. Preliminary isotope data from the interval 1350-150 B.P. show relative steady δ¹⁸O values of -5.03 ± 0.28‰, with relatively stable δ¹⁸O values between 1350 and 575 B.P. (1σ = 0.11‰) and higher variability between 575 and 150 B.P. (1σ = 0.44‰), possibly caused by the onset of regional anthropogenic forcings. Carbon isotopes are also more variable between 600 and 150 BP (-9.17 ± 0.28‰). From 1400 to 1300 B.P. δ¹³C values sharply drop from -8.3‰ to -9.0‰, after which they steadily drop to ~ -9.5‰ at 700 B.P., then jump to -8.8‰ at 630 B.P. and fall to -9.1‰ at 600 B.P. Analyses and interpretation is ongoing and data covering the latter half of the Holocene will be presented.