Bedrock Uplift Reduces Antarctic Sea-Level Contribution over Next Centuries

The contribution of the Antarctic ice sheet to global sea-level rise could be as high as eight meters around 2300 but remains deeply uncertain<1>. Retreat of the Antarctic ice sheet leads to uplift of the underlying bedrock, which in turn can exert a stabilising effect on the receding grounding line<20>. However, projections of ice mass loss either exclude bedrock adjustment, or ignore lateral variations in Earth structure<4,11-27>. Here, we couple an ice sheet model with a bedrock model that includes a radially and laterally varying Earth structure to account for feedbacks between ice loss and bedrock deformation. We show that the grounding line in West Antarctica takes 50 to 130 years longer to retreat when the heterogeneity of the solid Earth is included, leading to a reduction of 9-23% in the Antarctic sea-level contribution by the year 2500. In contrast to previous studies that show an effect of bedrock adjustment on the ice sheet evolution over millennia, our results reveal an impact on centennial time scales. the effect of the solid Earth feedback in ice sheet projections can be twice as large as the uncertainty due to the climate forcing. Our results emphasise that radially and laterally varying Earth structures should be considered when projecting the Antarctic contribution to sea-level rise on centennial time scales.