TEMPERATURE AND OXYGEN ISOTOPE SEASONALITY OF THE LAST INTERGLACIAL (MIS-5E) FROM ANALYSIS OF STABLE AND CLUMPED ISOTOPES OF BERMUDA BIVALVES

Reconstructing climate during periods of past global warmth can improve predictions of future climate change. During the Last Interglacial (MIS-5e, ~125ka), the Earth experienced a climate ~1-2°C warmer and global sea level 6-9 m higher than present. This led to extensive shallow marine carbonate deposits currently exposed above the water-line on Bermuda that contain abundant molluscan fossils. In our study, we have undertaken high-resolution δ¹⁸O and clumped carbonate isotope analysis to reconstruct seasonal variations in surface water temperature and seawater δ¹⁸O values. Shell δ¹⁸O analysis reveals a sinusoidal pattern indicating a seasonality in temperature of ~7°C, similar to today. Prior clumped isotope studies of Bermuda mollusca, based on bulk sample analysis, suggest an overall cooling at this location despite an overall warmer global climate. Our high-resolution clumped isotope analysis targeting the seasonal maximum and minimum values of carbonate δ¹⁸O in each shell allows for the separation of the seasonal influences of temperature and potential variation in seawater salinity and δ¹⁸O values. Reconstruction of Bermuda’s climatic conditions during MIS-5e will help constrain predictions and numerical model simulations of future climate as modern global warming continues.