Antarctic ice sheet tipping points in the last 800,000 years warn of future ice loss

This study investigates the long-term stability and tipping behavior of the Antarctic Ice Sheet (AIS) over the past 800,000 years using transient and equilibrium simulations with the Parallel Ice Sheet Model (PISM). By simulating AIS responses to glacial-interglacial climate cycles, the research identifies critical temperature thresholds and hysteresis effects that could lead to irreversible ice loss and significant sea-level rise.

The simulations demonstrate that the West Antarctic Ice Sheet (WAIS) exhibits strong hysteresis and tipping point behavior in response to ocean temperature changes over the past 800,000 years. While transient ice sheet states during cooler interglacials remain close to equilibrium, warmer interglacials since Marine Isotope Stage (MIS) 12 show significant divergence-exceeding 8 meters sea-level equivalent (SLE)-driven primarily by internal instabilities rather than delayed responses to external forcing. A consistent deglaciation tipping point is identified at ocean temperature anomalies of just 0 to +0.25 °C above present, beyond which WAIS collapses irreversibly in equilibrium simulations.