We conduct an ensemble of simulations of the englacial temperature field of the Antarctic ice sheet to gauge the sensitivity to uncertainties in geothermal heat flow, surface climatic conditions, ice thermodynamics and dynamics. We compare the modeled temperature fields with observational constraints, including deep-borehole temperature measurements, englacial temperatures retrieved from the Soil Moisture and Ocean Salinity satellite observations, and the distribution of subglacial lakes to determine the most likely boundary conditions. Results show that temperate basal conditions prevail over 60% of the Antarctic ice sheet, with a mean basal melt rate of 6.9 mm a−1. The ensemble mean subglacial meltwater production over the grounded ice sheet is 69 Gt a−1, with a contribution of 51% from geothermal heat and 49% from frictional heat. While geothermal heat flow remains the largest source of uncertainty, heat flow datasets leading to colder conditions tend to fit englacial temperature measurements better. However, ice thermomechanical approximations influence the shape of temperature profiles and may, in some cases, be more important than the geothermal heat flow. Furthermore, since frictional heat contributes significantly to basal melt in regions hosting fast-flowing glaciers, uncertainties in basal slipperiness affect the basal melt estimates as much as the geothermal heat flow.

In mountainous terrain, the relationship between ice sheet dynamics and basal topography is complex, with each component influencing the other. This paper investigates how the last glacial maximum Antarctic Peninsula Ice Sheet might have modified its bed both at maximum extent and during progressive grounding line retreat. Focussing on the Marguerite Trough Ice Stream we then examine the degree to which basal topographical conditions affected the rate of ocean-forced recession. Zones of peak subglacial erosion are preferentially located in areas of convergent flow and where horizontal strain rates are highest. During ice sheet retreat, potential erosion rates increase in these areas, but the foci remain fixed. This leads to selective and progressive deepening of subglacial basins. As grounding lines migrate landward, faster retreat tends to occur over subglacial basins, especially if flow is divergent, whereas slower retreat takes place on sloping beds and where the geometry of the outlet allows convergent flow and a non-negative flux balance. In conclusion the Antarctic Peninsula Ice Sheet selectively erodes its bed beneath linear outlets and, over successive glacial cycles, progressive deepening of subglacial basins may bring about non-linear retreat of the ice sheet margin.