Events

Speaker: Gavin Piccione, Postdoctoral Research Associate in Environment and Society, Brown University

Host: Ruthie Halberstadt

Title: Constraints on the Oxygen Isotope Composition of Antarctic Ice Recorded in Subglacial Rocks: A Case Study from the Late Miocene

Abstract: Long-term, continuous records of global ice volume have been derived using δ18O values of benthic foraminifera (δ18Ob), which record the balance between water held in the ocean and trapped on the continents. However, these ice volume approximations are confounded by the fact that δ18Ob values change as a function of ocean bottom water temperature and cannot account for spatiotemporal variation in the δ18O of ice sheets. Therefore, direct constraints on the δ18O of ice sheets are necessary to link the δ18Ob record to sea level change. In this talk, I will present geochemical data from Antarctic subglacial opal and calcite precipitates, a novel archive for reconstructing ice sheet δ18O values. Uranium-series and uranium-lead dating reveal the formation histories of these samples, spanning the late Pleistocene to late Miocene. Paired carbonate clumped isotope temperature estimates and opal triple oxygen measurements characterize the oxygen isotope composition of basal ice. Using a simplified mass balance calculation, I will explore the mass and sea level contributions of the late Miocene Antarctic Ice Sheet given these newly defined oxygen isotopic constraints.