Seasonal resolution of Eastern Mediterranean climate change since 34 ka from a Soreq Cave speleothem

The combination of ion microprobe analysis of δ18O and confocal laser fluorescent microscope imaging of annual growth bands in a Soreq Cave speleothem provides sub-annual-scale climate information between 34 and 4 ka. This high-resolution methodology is ideal both for comparing seasonal climate patterns across broad windows of time and examining rapid climate events, such as the Younger Dryas termination, in detail. The sub-annual δ18O gradients we report represent a combination of seasonal variability in rainfall amount and air temperature. A distinct change in both the pattern of fluorescent banding and the gradient of δ18O measured in situ across single, annual growth bands indicates a change in seasonal climate patterns of the Eastern Mediterranean region following Heinrich event 1 and again after the Younger Dryas. Throughout the Holocene, wet winters and dry summers characterized regional climate. During the Younger Dryas, we find that regional climate may have been more arid than in the Holocene, but the fluorescent banding pattern indicates that the supply of dripwater to the cave was more consistent year-round. We suggest that a reduced gradient of seasonal precipitation, occasional snowfall, and vegetation differences may have all contributed to the isotope and fluorescent banding patterns observed during Heinrich event 1 and the last glacial stadial. Detailed investigation of the Younger Dryas termination reveals a rapid onset of regional environmental change. Fluorescent band counting indicates that the Younger Dryas termination, as recorded by rainfall in the Eastern Mediterranean, spanned a minimum of 12 years.