Seasonally Variable Aquifer Discharge and Cooler Climate in Bermuda During the Last Interglacial Revealed by Subannual Clumped Isotope Analysis

Faunal analog reconstructions suggest that Last Interglacial (MIS 5e) sea surface temperatures were cooler around Bermuda and in the Caribbean than modern climate. Here we describe new revised clumped isotope measurements of Cittarium pica fossil shells supporting previous findings during Interglacial. We resolve temperature δ18Ow differences between two closely located apparently coeval sites described Winkelstern et al. (2017), https://doi.org/10.1002/2016pa003014 through reprocessing raw isotopic data with updated Brand/IUPAC parameters. New subannual-resolution reveal large variations out phase seasonal changes (i.e., lower values winter). Supported by identifying similar processes occurring today, past coastal driven seasonally variable freshwater discharge from a subterranean aquifer beneath island. Taken together, our results emphasize importance controlling carbonate δ18O, typical assumptions constant should be made cautiously nearshore settings can contribute to less accurate paleotemperature.