Historic simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model

Large uncertainties in Antarctic sea level projections are related to ocean-driven melting (Seroussi et al., 2020; Jourdain et al., 2020; Reese et al., 2020; Edwards et al., in press) and the marine ice sheet instability (Robel et al., 2019). ‘Hindcasting’ simulations that follow the trajectory of the Antarctic Ice Sheet from pre-industrial conditions to present-day, are a useful tool to better constrain such uncertainties. We here perform historic simulations with the Parallel Ice Sheet Model. The simulations are forced by changes in the ocean and atmosphere from GCM output of CMIP5 as selected for ISMIP6 (Barthel et al., 2020). Sub-shelf melting is modeled using PICO (Olbers & Hellmer, 2010; Reese et al., 2018), with careful consideration of PICO’s parameters: the parameters for heat exchange across the ice ocean interface as well as the overturning strength are fitted with estimates of the melt sensitivity based on observations (Jenkins et al., 2018). Present-day observation of sub-shelf melting and mass loss inform parameter selection using an ensemble approach (Albrecht et al., 2020; Reese et al., 2020). The historic simulations provide an important basis to assess the future evolution and stability of Antarctic grounding lines. This work is done in the framework of the H2020 TiPACCs project.