Seasonal isotopic variability of precipitation and cave drip water at Indian Oven Cave, New York

A major assumption in palaeoclimatic studies using speleothems is that cave-seepage waters are homogenized as they pass through the bedrock, so that they record the average annual isotopic signal of precipitation. A year-long study during 2001-02 was conducted at Indian Oven Cave in eastern New York State, USA, to investigate how cave-seepage water isotopic signals relate to those of precipitation. Samples were collected biweekly and analysed for stable isotopes of oxygen and hydrogen. Our study shows that, for this cave, homogenization did not occur, as seepage waters had the same seasonal variability as precipitation. However, mean seepage water isotopic values were very close to those of the mean values for precipitation. Rapid flow-through times of seepage water show that the speleothems can record climate conditions above the cave contemporaneously. At one location, flow ceased during the winter; therefore, isotopes measured in cave drip waters reflected only the enriched summer isotopes. Under certain circumstances, the analysis of calcite sampled from those drip waters may then lead to a false conclusion of a warming during that period, instead of the fact that it was merely a drier winter period. Copyright (c) 2005 John Wiley & Sons, Ltd.