Constraining glacial-interglacial Antarctic Ice Sheet dynamics using ice core and isochronal records

The present-day state of the Antarctic Ice Sheet (AIS) results from millennia of changes in ice accumulation and flow. Understanding ice dynamics over glacial-interglacial cycles is crucial for accurately representing the current state of the AIS in models and making reliable projections. This study leverages the growing pool of traced and dated internal layers (isochrones) to characterise regions around deep ice core sites in Antarctica, focusing on ice divides in which ice flows on hundreds of thousands of years timescale. We employ a thermomechanically-coupled 3D ice sheet model (PISM) to simulate ice flow over glacial-interglacial cycles in these regions. First, we implement direct reconstructions of surface temperature and accumulation from deep ice cores, bypassing conventional climate index approaches in improving the thermal state and constraining the isochronal structure in the upper part of the ice. Second, we improve the ice rheology and constrain the model parameter space by minimising the mismatch between observed and modelled isochrone elevations closer to bedrock. Finally, we reduce uncertainties in basal thermal conditions through direct comparison with measured borehole profiles and further spatial calibration of isochronal geometries.
This methodology emphasises the importance of reliable boundary conditions in ice sheet models for accurately representing past ice dynamics. Our work seeks to deepen our understanding of AIS dynamics on glacial-interglacial timescales and provide improved paleo-informed initialisations for AIS projections.