The challenge of spatio-temporal variability of processes across Antarctic ice-bed-ocean interfaces: past evolution of Antarctic sensitivity to climatic conditions

Understanding how the Antarctic ice sheet will respond to global warming relies on knowledge of how it has behaved in the past. The use of numerical models, the only means to quantitatively predict the future, is hindered by limitations to topographic data both now and in the past, and in knowledge of how subsurface oceanic, glaciological and hydrological processes interact. Over the past 34 Million years, the Antarctic continental shelf has gradually deepened, due to ice sheet loading, thermal subsidence, and erosion from repeated glaciations. The deepening recorded in the sedimentological deposits around the Antarctic margin indicates that after the mid Miocene Climate Optimum (≈15 Ma), Antarctic Ice Sheet (AIS) dynamical response to climate conditions changed. We explore end-members for maximum AIS extent, based on ice-sheet simulations of a late Pleistocene and a mid-Miocene glaciation. Fundamental dynamical differences emerge as a consequence of atmospheric forcing, eustatic sea level and continental shelf evolution. We show that the AIS contributed to the amplification of its own sensitivity to ocean forcing by gradually expanding and eroding the continental shelf, which likely changed its tipping points through time. The lack of past topographic and bathymetric reconstructions implies that so far, we still have an incomplete understanding of AIS tipping points in response to past climate forcing, which is crucial to constrain its future evolution. Incorporating the variety and interplay of such processes, operating at multiple spatio-temporal scales, is critical to modeling the Antarctic's system evolution and requires direct observations in challenging locations.