Friday, 31 August 2007
5.PS-119
Cenozoic variations of the Antarctic Ice Sheet: a model-data mismatch?
David Pollard, Earth and Environmental Systems Institute, Pennsylvania State University, 2217 Earth and Engineering Science Building, Pennsylvania State University, University Park, PA 16802 and Robert M. DeConto, Department of Geosciences, University of Massachusetts, 233 Morrill Science Center, University of Massachusetts, Amherst, MA 01003.
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.