Impact of the Southern Annular Mode on the Antarctic ice sheet surface mass balance through the Plio/Pliocene transition

The impact of the main climate tele-connections on the on the surface mass balance of the Antarctic ice sheet has been seldom investigated. The Southern Annular Mode (SAM), whose main impact is to cause a strengthening of the winds around Antarctica and a warming over the Antarctic Peninsula and a cooling in the Admundsen Sea sector during its positive phase. These effects may be of importance to understand the past and the future evolution of Antarctica. By means of stand-alone ice sheet model, we investigate the impact of the SAM on the evolution of the Pliocene and pre-industrial Antarctic ice sheet topography. First, we analyse the atmospheric and oceanic characteristics of the positive and the negative phases, that we separate with an EOF analysis in some of the model outputs of the PLIOMIP2 project. Second, the climate forcing are split into SAM+ and SAM- years to force off-line the SIA/SSA GRISLI ice sheet model (Ritz et al., 2001). Idealised simulations are branched from a long-term paleoclimate spin-up and are run for 500 years in steady-state modes. In our pre-industrial simulations, the short-term SAM variability induces a strong bipolar response of the Antarctic surface mass balance, which is stronger and shifted geographically in the Pliocene simulations. In particular, the Pliocene climate conditions appear to be less favorable to ice shelves in the Weddell Sea than in the Pre-industrial simulations.