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Abstract. In this study we present the evolution of the Antarctic Ice Sheet (AIS) since the last interglacial. This is achieved by means of a history-matching analysis where a newly updated observational database (AntICE2, Lecavalier et al., 2023) was used to constrain a large ensemble of 9,293 model simulations. The Glacial Systems Model (GSM) configured with 38 ensemble parameters was history matched against observations of past ice extent, past ice thickness, past sea level, ice core borehole temperature profiles, present-day uplift rates, and present-day ice sheet geometry and surface velocity. Successive ensembles were used to train Bayesian Artificial Neural Network emulators. The parameter space was efficiently explored to identify the most relevant portions of the parameter space through Markov Chain Monte Carlo sampling with the emulators. The history matching ruled out model simulations which were inconsistent with the observational constraint database. During the Last Interglaciation (LIG), the AIS yielded several meters equivalent sea-level (mESL) grounded ice volume deficit relative to present with subsurface ocean warming during this period being the key uncertainty. At the global Last Glacial Maximum (LGM), the best-fitting sub-ensemble of AIS simulations reached an excess grounded ice volume relative to present of 9.2 to 26.5 mESL. Considering the data does not rule out simulations with an LGM grounded ice volume > 20 mESL with respect to present, the AIS volume at the LGM can partly explain the missing ice problem and help close the LGM sea-level budget. Moreover, during the deglaciation, the state space estimation of the AIS based on the GSM and near-field observational constraints allow only a negligible Antarctic Melt Water Pulse 1a contribution (-0.2 to 0.3 mESL).
Lecavalier et al. (Wed,) studied this question.