Session: Warm Climates (Mid-Holocene, Last interglacial, Deep-time, Pliocene)
Author: Gilles Ramstein / email@example.com / LSCE, France
Co-author: Ning Tan, Jean-Baptiste Ladant, Christophe Dumas, LSCE, France;
The early to mid-Pliocene was punctuated by cold and warm phases (5.3 to 3.3 Ma) [Lisiecki et al. 2005]. This period ended up with the major MIS M2 glaciation [Tan et al. 2017] and was followed by a warm and rather stable period called the mid Piacenzian warm period (mPWP, 3.3-3.0 Ma), which was the focus of the PLIOMIP1 project [Haywood et al. 2016]. Here, our purpose is to investigate the evolution of the Greenland ice sheet (GrIS) during the 3.0-2.5 Ma interval, which embraces the commonly accepted onset of perennial Greenland glaciation. We adapted and developed a specific tool that was first used to study the Eocene-Oligocene Antarctic glaciation (34 Ma) [Ladant et al. 2014]. This physically based method uses a matrix constructed from 56 IPSL simulations with various combinations of orbital forcing, CO2 concentration and GrIS configuration and creates a continuous climatic forcing based on the temporal evolution of the insolation, CO2 and ice sheet. This method allowed us to investigate the response of the GrIS to pCO2, in a first step by keeping the CO2 temporal evolution constant and in a second time, by using published pCO2 records from the literature. The constant CO2 simulations demonstrate the existence of a threshold for perennial GrIS onset: under 280 ppm it is possible to trigger and maintain the GrIS whereas above 320ppm the building of a large GrIS is not possible. These simulations also reveal the impact of the favorable insolation at 2.7 Ma in order to build the GrIS. Next, we force our model with recent pCO2 reconstructions from the literature [e.g., Martinez et al. 2015] to discuss the consistency between model results and available data, and also compare our simulated GrIS evolution with the recent model study of Willeit et al. 2015. Finally, we propose a CO2 scenario, which produces a GrIS evolution in good agreement with SST reconstructions and IRD records.