Does the AMOC strength matter for the Antarctic ice sheet retreat during the penultimate deglaciation?

The Antarctic Ice Sheet has contributed 0 to 7.7m to the global mean sea level during the Last Interglacial, according to recent publications (Barnett et al., 2023; Dyer et al., 2021; Dumitru et al., 2023; Shackleton et al., 2020). This large uncertainty suggests that the Antarctic ice sheet could have been similar to present-day geometry, but it could also have had a major retreat such as the collapse of the West Antarctic Ice Sheet and more. For example, Clark et al. 2020 simulate the West Antarctic Ice Sheet collapse in their modeling work. They suggest that a longer period of reduced Atlantic Meridional Overturning Circulation (AMOC) during the penultimate deglaciation compared to the last deglaciation could have led to greater subsurface warming and subsequent larger Antarctic Ice Sheet retreat. 

Here we study the response of the Antarctic ice sheet during the penultimate deglaciation (∼ 138–128 ka) to different evolutions of the AMOC. We use the ice sheet model GRISLI (Quiquet et al. 2018), including the recently implemented sub-shelf melt module PICO (Reese et al. 2018). The climate forcings, including Northern Hemisphere ice sheets evolution, are obtained from fully coupled Earth System Model simulations using the intermediate complexity model iLOVECLIM (Roche et al. 2014). We run 2 sets of ice sheet simulations. In the first set the Northern Hemisphere ice sheets are fully coupled and therefore provide freshwater fluxes directly to the oceans according to ice sheets melt (Quiquet and Roche 2024). In the second set the freshwater fluxes given in the North Atlantic Ocean are idealized. With the second set, we also test the impact of the timing and duration of the freshwater flux on the ice sheet retreat. We hypothesize that both the duration and timing of reduced AMOC can significantly affect the sensitivity of the Antarctic Ice Sheet. A larger subsurface warming in the Southern Ocean can be triggered by longer AMOC reduction, and the resilience of the ice sheet to this warming depends on its geometry during the deglaciation.