Drilling and modeling studies expose Antarctica’s Miocene secrets

Abstract

In PNAS, two companion studies by Levy et al. (1) and Gasson et al. (2) underscore the importance of ice-proximal geologic data for improving computer models of Antarctic ice sheet response to oceanic and atmospheric warming. Current knowledge of Antarctic ice sheet evolution (∼40–0 Ma) is based on deep-sea records of global ice volume, deep ocean temperature, and carbon cycling preserved in the calcium carbonate shells of benthic foraminifera (3, 4). Shackleton and Kennett (5) hypothesized, from moderate-resolution southwest Pacific Ocean benthic foraminifer stable oxygen (δ18O) and carbon (δ13C) isotope compilations, that the deep ocean cooled ∼15 °C through the Cenozoic and that Antarctic ice sheets expanded significantly at the Eocene–Oligocene boundary, varied dynamically until the middle Miocene climate transition (MMCT; 14.2–13.8 Ma), and then rapidly expanded and stabilized. Over the last 41 y, paleoceanographers have used deep-sea sediments recovered by scientific ocean drilling programs, including the International Ocean Discovery Program (2013–2023), to increase the resolution of the global deep-sea stable isotope record (3⇓–5), develop geochemical methods to separate ice volume and temperature signals contained in the δ18O signal (4), and resolve climate forcings and feedbacks involved in Antarctic ice growth and global climate evolution (4, 6). Because of a lack of high-quality ice-proximal drill sites, only a handful of studies (e.g., refs. 1 and 7) directly link Antarctic ice sheet variability to far-field deep-sea δ18O (3⇓–5) and passive margin sea-level records (8). Such linkages are required to improve understanding of the timing and magnitude of ice volume fluctuations, relative contributions of Antarctica’s ice sheets to global eustacy, individual histories of the East and West Antarctic ice sheets, and climatic boundary conditions favorable for ice growth and decay (3). In PNAS, Levy et … [↵][1]1Email: ashevenell{at}usf.edu. [1]: #xref-corresp-1-1