Antarctic Ice Sheet  simulations using Yelmo ice sheet model and a series of IPSL CM5A2 climate simulations between 17 Ma and 14 Ma

Abstract

<p>The mid-Miocene Climatic Optimum (MMCO, ~17-15 Ma) and the mid-Miocene Climatic Transition (MCT, ~15-13.5 Ma),  represents a period of high policy relevance because of the high atmospheric pCO2 concentrations. Exploring this period offers the opportunity to investigate the Antarctic Ice Sheet (AIS) response to CO2 forcings that are close to those projected in the medium to worse case emission scenarios. A set of equilibrium simulations with the 3D ice sheet model Yelmo allows us to study the envelope of the AIS volume and extent during the MMCO (17 Ma) and MCT (14 Ma). These simulations are forced off-line with equilibrium climatic conditions  obtained with the Atmosphere-Ocean General Circulation Model (AOGCM) IPSL CM5A2.  Two values of the reconstructed atmospheric pCO2, i.e. 420 ppm and 700 ppm, are prescribed, for an orbital configuration corresponding to minimum and maximum insolation values at 75°S each (9 climate simulations in total). Thanks to these different configurations we simulated the AIS dynamics. Results show that at 17 Ma, warmer conditions produce an AIS that is drastically reduced with respect to today’s configuration. At 14 Ma, cooler climatic conditions allow the AIS to expand again. This is in agreement with the geological records of the AIS dynamics that reveal a substantial expansion of the ice sheet at the end of the MCT. Since Antarctica is the only ice sheet at this time, our set of climate and ice-sheet simulations capture the envelope of ice volume and extent of the AIS. Moreover, such studies contribute to a better understanding of the 𝛿<sup>18</sup>O records and of the evolution of deep ocean temperature versus ice volume and global mean sea level change.</p>