Retreat of the Antarctic ice sheet (AIS) is likely to be a major contributor to future sea-level rise (SLR). Current projections of SLR due to ice-sheet mass loss remain highly uncertain. Better understanding of how ice sheets respond to future climate forcing and variability is essential for assessing long-term risk of SLR. However, predictability of future climate is limited by uncertainties from emission scenarios, model structural differences, and internal climate variability (ICV) that is inherently generated within the fully coupled climate system. Among those uncertainties, the impact of ICV on the AIS changes has not been explicitly assessed. Here we quantify the effects of ICV on the AIS evolutions by employing climate fields from two large-ensemble experiments using the Community Earth System Model to force a three-dimensional ice-sheet model. We find that ICV of climate fields among ensemble members leads to significantly different AIS responses, and that most of the effect is due to atmospheric variability compared to oceanic. Our results show that ICV can cause about 0.08 m differences of AIS contribution to SLR by 2100 compared to the ensemble-mean AIS contribution of 0.38–0.45 m. Moreover, using ensemble-mean climate forcing fields as the forcing in an ice-sheet model significantly delays retreat of the West AIS for up to 20 years and significantly underestimates the AIS contribution to SLR by 0.07–0.11 m in 2100 and up to 0.34 m in the 2250’s. This study highlights the need to take internal climate variability into account in assessing uncertainty associated with the AIS contribution in sea-level rise projections.

南极冰原（AIS）的退缩可能是未来海平面上升（SLR）的主要因素。由于冰盖质量损失，目前对SLR的预测仍然非常不确定。更好地了解冰盖如何应对未来的气候强迫和变异性，对于评估SLR的长期风险至关重要。但是，未来气候的可预测性受到排放情景，模型结构差异以及在完全耦合的气候系统中固有产生的内部气候变化性（ICV）的不确定性的限制。在这些不确定因素中，尚未明确评估ICV对AIS变更的影响。在这里，我们通过使用来自两个大型集体实验的气候场（使用社区地球系统模型强制使用三维冰盖模型）来量化ICV对AIS演变的影响。我们发现，集合成员之间气候场的ICV导致AIS响应显着不同，并且与海洋相比，大多数影响是由于大气多变性。我们的结果表明，与整体平均AIS贡献0.38–0.45 m相比，到2100年，ICV可以导致AIS对SLR贡献的差异为0.08 m。此外，使用集合平均气候强迫场作为冰盖模型中的强迫，显着延迟了西部AIS的退缩长达20年，并显着低估了2100年AIS对SLR的贡献0.07-0.11 m和0.34 m在2250年代。