Modelling glacial inception of Antarctica during the Eocene-Oligocene boundary

Abstract

The Antarctic glaciation during the Eocene-Oligocene boundary is one of the quickest changes in the climate system observed in the geological record. CO2 is assumed to be the major cause of glaciation, although the uncertainty is high. Here we will study the impact of CO2, the mass balance, bedrock deformation, sea level changes and vegetation on the climate system during the Eocene-Oligocene transition, especially on the East Antarctic ice sheet. We do this with a coupled Zonally averaged Energy Balance Climate Model and a 1-D Ice Sheet Model. The ablation has a large impact on the climate system, therefore we have determined the ablation parameter Cabl = -30. Bedrock deformations cause large fluctuations in ice volume, on the other hand, sea level change causes only small fluctuations. The bedrock relaxation time has also a large impact on the ice volume. We find that vegetation has an impact on the glacial inception of Antarctica. Only a small fraction of the surface has to be covered with forests to delay the inception with hunderds of ppmv CO2. We estimated that with 10% or less of the surface covered with forests, it still results in a plausible CO2 concentration of glacial inception. With more than 10% forests, the ice sheet develops only with very low CO2 concentrations, or it does not develop at all. The temperature of the warmest month is high enough to sustain forests at the margins of the continent. With calculations of the model, we conclude that the mass balance and bedrock deformation are important on the glacial inception. Vegetation however, has the largest impact on the glacial inception of Antarctica.