The lapse-rate feedback is the dominant driver of stronger warming in the Arctic than the Antarctic in simulations with increased CO2. While Antarctic surface elevation has been implicated in promoting a weaker Antarctic lapse-rate feedback, the mechanisms in which elevation impacts the lapse-rate feedback are still unclear. Here we suggest that weaker Antarctic warming under CO2 forcing stems from shallower, less intense climatological inversions due to limited atmospheric heat transport above the ice sheet elevation and elevation-induced katabatic winds. In slab ocean model experiments with flattened Antarctic topography, stronger climatological inversions support a stronger lapse-rate feedback and annual-mean Antarctic warming comparable to the Arctic under CO2 doubling. Unlike the Arctic, seasonality in warming over flat Antarctica is mainly driven by a negative shortwave cloud feedback which exclusively dampens summer warming, with a smaller contribution from the winter-enhanced lapse-rate feedback.

Knowledge of how the Antarctic Ice Sheet (AIS) has varied in response to past climates can inform the prediction of future AIS behaviour. Water stable isotope records from Antarctic ice cores traditionally provide information on past temperature changes. However, these reconstructions neglect changes in atmospheric circulation, which can be induced by elevation changes. Here, we simulate an ensemble of idealised AIS elevation change scenarios using the isotope-enabled HadCM3 climate model during the Last Interglacial period (LIG). Our ensemble is used to investigate the isotope-elevation relationship. Changing AIS elevations linearly modify the response in surface air temperature, as precipitation and $\delta^{18}$O. Especially, we observe $\delta^{18}$O decrease with the AIS elevation, with higher slopes on the coast compared to the plateau, reflecting different processes. We note that the effect of sea-ice induced by AIS changes is small. These results help to isolate the effect of AIS changes on the LIG $\delta^{18}$O signals.

Coupled global climate models (GCMs) generally fail to reproduce the observed sea-surface temperature (SST) trend pattern since the 1980s. The model-observation discrepancies may arise in part from the lack of realistic Antarctic ice-sheet meltwater imbalance in GCMs. Here we employ two sets of CESM1-CAM5 simulations forced by anomalous Antarctic meltwater fluxes over 1980–2013 and into the 21st century. Both show a reduced global warming rate and an SST trend pattern that better resembles observations. The meltwater drives surface cooling in the Southern Ocean and the tropical southeast Pacific, in turn increasing low-cloud cover and driving radiative feedbacks to become more stabilizing (corresponding to a lower effective climate sensitivity). These feedback changes contribute more than ocean heat uptake efficiency changes in reducing the global warming rate. Accurately projecting historical and future warming thus requires improved representation of Antarctic meltwater and its impacts in models.