The seasonality of east central North American precipitation based on three coeval Holocene speleothems from southern West Virginia

Abstract

We present a replicated record of Holocene climate change from a cave in West Virginia, USA. Based on analysis of stable isotopes in precipitation ( δ 18O w) from the closest Global Network of Isotopes in Precipitation (GNIP) station in Coshocton, OH, we interpret enriched oxygen isotopes in calcite ( δ 18O c) as representing an increase in the relative contribution of summer precipitation to annual totals. Significant coherence between local summer (July and August) precipitation and the Summer North Atlantic Oscillation (SNAO) index on multi-decadal timescales suggests that summer precipitation in our study area is strongly influenced by changes in the Bermuda High. A strengthened Bermuda High circulation would increase summer precipitation amounts in the region and lead to enriched δ 18O c of speleothem calcite. Our δ 18O c record achieves maximum values during the mid-Holocene, consistent with previous studies indicating an intensified Bermuda High circulation at that time. At 4.2 ka, δ 18O c transitions to lower values at a time when numerous records around the globe document significant changes in the hydrologic budget. Over the last 2000 years, there are intervals of substantially decreased δ 18O c, coincident with aridity in the Yucatan, Alpine glacial advances, and a weakened Asian summer monsoon.