Abstract

Geophysical mapping of the sea floor in Marguerite Bay, Antarctica, has led to the identification of a series of grounding zone wedges which represent the locations of palaeo grounding lines during retreat from maximum ice stream extent. This data indicates that during rapid retreat following the LGM , the ice stream grounding line stabilised multiple times on a bed that deepens inland. According to the marine ice sheet instability theory, these stabilisations should not be expected. We use a numerical flowband model which can robustly calculate groundine line behaviour over time to reproduce the retreat pattern inferred from the seafloor. We conduct a series of sensitivity tests to determine what controlled grounding line motion and stability, and to understand what drove wider retreat behaviour in Marguerite Bay. Our findings have implications for understanding past retreat dynamics in other regions, and for making future predictions of ice sheet stability.