PP42A-03
The MMCO-EOT conundrum: same benthic δ18O, diff erent CO2
Thursday, 17 December 2015: 10:50
2010 (Moscone West)
Lennert Bastiaan Stap, Institute for Marine and Atmospheric Research Utrecht, Utrecht, Netherlands, Roderik Vandewal, Utrecht University, Utrecht, Netherlands, Richard Bintanja, Royal Netherlands Meteorological Institute, De Bilt, Netherlands, Lucas Joost Lourens, Utrecht University, Utrecht, 3584, Netherlands and Bas De Boer, School of Earth and Environment, Faculty of Environment, University of Leeds, Leeds, United Kingdom
Abstract:
Knowledge on temporal variations of Earth's climate over the past 38 Myr largely stems from benthic δ18O records. These records are difficult to interpret, however, since they document combined eff ects of deep-sea temperature and ice volume variations. Information on CO2 is expanding, but remains highly uncertain and intermittent. Attempts to determine the long-term relations between δ18O, sea level and CO2 from proxy data su ffer from paucity of data and apparent inconsistency among di fferent records. One outstanding issue is the di fference recorded in proxy CO2 data between the Eocene-Oligocene boundary (EOT) and the Middle-Miocene Climatic Optimum (MMCO), while similar levels of benthic δ18O are shown during these time periods. Here, we take a model-based approach to deconvolute the benthic δ18O signal, and reconcile knowledge on benthic δ18O, sea level, CO2 and temperature. We obtain continuous and mutually consistent 38-Myr-long simulations of these variables, by forcing a coupled ice sheet-climate model inversely with benthic δ18O observations. We show that different CO2 between the EOT and MMCO, as indicated by proxy data, can only be obtained if we impose erosion or tectonic movement of the Antarctic continent over time.
