Local insolation changes enhance Antarctic interglacials: Insights from an 800,000-year ice sheet simulation with transient climate forcing

The Antarctic ice sheet – storing ∼27 million cubic kilometres of ice – has the potential to contribute greatly to future sea level rise; yet its past evolution and sensitivity to long-term climatic drivers remain poorly understood and constrained. In particular, a long-standing debate questions whether Antarctic climate and ice volume respond mostly to changes in global sea level and atmospheric greenhouse gas concentrations or to local insolation changes. So far, long-term Antarctic simulations have used proxy-based parameterizations of climatic drivers, presuming that external forcings are synchronous and spatially uniform. Here for the first time we use a transient, three-dimensional climate simulation over the last eight glacial cycles to drive an Antarctic ice sheet model. We show that the evolution of the Antarctic ice sheet was mostly driven by CO₂ and sea level forcing with a period of about 100,000 yr, synchronizing both hemispheres. However, on precessional time scales, local insolation forcing drives additional mass loss during periods of high sea level and CO₂, enhancing the Antarctic interglacial and putting northern and southern ice sheet variability temporarily out of phase. In our simulations, partial collapses of the West Antarctic ice sheet during warm interglacials are only simulated with unrealistically large Southern Ocean subsurface warming exceeding ∼4 °C. Overall, our results further elucidate the complex interplay of global and local forcings in driving Late Quaternary Antarctic ice sheet evolution, and the unique and overlooked role of precession therein.