North-Central Section - 54th Annual Meeting - 2020

Paper No. 10-1
Presentation Time: 8:30 AM-5:30 PM

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


WEDEL, Steven1, PETERSEN, Sierra V.1, ZHANG, Jade1, WINKELSTERN, Ian Z.2 and LOHMANN, Kyger C.1, (1)Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109, (2)Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, MI 48109; Department of Geology, Grand Valley State University, Padnos Hall of Science, 1 Campus Dr., Allendale, MI 49401

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.