U.S. Geological Survey and the National Academies, USGS OF-2007-1047, Extended Abstract 165 Cenozoic variations of the Antarctic Ice Sheet: A model-data mismatch?

Summary Cenozoic variations of global ice volume deduced from δ18O deep-sea-core records are compared with results from 3-D ice sheet-climate models. After the initial growth of major Antarctic ice at the Eocene-Oligocene boundary ~34 Ma, δ18O records indicate numerous excursions throughout the Oligocene and early Miocene with timescales of ~105 to 106 years and amplitudes of ~20 to 80 meters of sea level. During most of this period, proxy atmospheric CO2 levels in proxy records were low, around 1x pre-industrial. These observations conflict with coupled model results that once a large East Antarctic ice sheet formed at 34 Ma, CO2 levels must have been in the ~3x to 4x range to induce significant retreat and re-growth. Several mechanisms are discussed that could possibly have caused large ice-volume fluctuations, all of which are highly speculative