Late Pliocene growth of the West Antarctic Ice Sheet to near-modern configuration

Accurate prediction of a West Antarctic Ice Sheet (WAIS) collapse and its impact on sea level in a future warmer climate remains uncertain. Here, we provide evidence for the transition from a smaller-sized WAIS during the warm Pliocene to an expanded ice sheet closer to its modern configuration during the Pleistocene based on geochemical records from the proximity to the current maximum ice loss in the Amundsen Sea. In contrast to Pliocene ice sheet dynamics, the WAIS exhibited a relatively muted response throughout the Pleistocene despite substantial glacial-interglacial variations in atmospheric CO₂ levels, temperature, and orbital forcing. Our data suggest that critical tipping points for WAIS growth occurred under atmospheric-oceanic conditions of the Pliocene–Pleistocene transition. These findings highlight the importance of the Pliocene–Pleistocene transition in establishing the modern configuration of the WAIS and its importance as a key interval for understanding ice sheet stability under the changing climate.