Antarctic Bedrock Uncertainty

The future contribution of the Antarctic Ice Sheet to sea-level rise remains highly uncertain, partly due to limited knowledge of subglacial bedrock topography. Although Bedmap3 represents a major improvement over earlier compilations, substantial uncertainty persists, particularly in deep troughs beneath fast-flowing outlet glaciers.

Here, we assess how uncertainty in Antarctic bedrock topography propagates into ice-sheet projections by systematically perturbing the Bedmap3 bed within its mapped 1σ uncertainty range. Using the Parallel Ice Sheet Model (PISM), we perform transient simulations from 1950 to 3000 under constant present-day climate forcing, applying uniform and spatially correlated bed perturbations consistent with Bedmap3 uncertainty.

Bedrock uncertainty within the Bedmap3 1σ range produces an Antarctic-wide spread of approximately 0.5 m sea-level equivalent by model year 3000, highlighting bed topography as a major source of long-term projection uncertainty.