The surface mass balance (SMB) of polar ice sheets is vital to their overall mass gain or loss. However, evaluating SMB across Antarctica is extremely difficult because observations that can validate climate-model estimates are widely lacking. In this manuscript, the authors present a highly original approach to this problem: they use GPS observations to evaluate SMB models. Analysis of GPS data from sites across Antarctica is used to evaluate the variability in SMB from several atmospheric models. The findings are timely and important, especially as more SMB models are available at increasingly fine spatial resolution. Overall, the study contributes valuable insights into estimates of ice-sheet mass variability and its varying contribution to sea-level change.