Simulating the onset and evolution of West Antarctic glaciation

Ice sheets on West and East Antarctica presumably react considerably different to changing climatic conditions – today, in the future, and also when initiated. Large-scale East Antarctic glaciation preceded West Antarctica’s likely by more than 10 million years. However, the precise timing and nature of West Antarctic Ice Sheet (WAIS) evolution still remain largely speculative. Drilled sedimentary sequences from the Amundsen Sea Embayment of West Antarctica revealed evidence for marine-terminating glaciers already before the Oligocene-Miocene transition (~23 million years ago). For contextualizing this result, we coupled climate and ice sheet simulations using recent topography reconstructions for this critical climate transition and applying different CO2 forcings.Our 280 ppm CO2 model results, i.e., closely resembling CO2 reconstructions for the latest Oligocene, reveal separate WAIS nuclei that evolved independently from the East Antarctic Ice Sheet. They were fuelled by increasing near-coastal precipitation and eventually expanded into West Antarctic marine basins as well as towards East Antarctic ice, which advanced from the Transantarctic Mountains. Our data-validated simulations emphasize the importance of considering both comprehensive climate information and bedrock topography for understanding initial West Antarctic glaciation – knowledge that is crucial not only for a better understanding of WAIS’s initiation, but also for assessing its future fate.