Sensitivity analysis of a King George Island outlet glacier, South Shetlands, Antarctica.

The Lange glacier is an outlet glacier situated in the Admiralty Bay, King George Island, Peninsula Antarctica. It retreated about 1 km since the 1950s. Although recent observations do not show any significant change at the ice-ocean margin, it is not clear whether this glacier has reached a new steady state or whether it is still adjusting to new climate conditions. By combining a three-dimensional glacier model with satellite and in-situ datasets, we investigate the sensitivity of Lange glacier to perturbations in flow rate factor, friction coefficient, surface mass balance, and calving front position. The (time-dependent) perturbation experiments show that the glacier is more sensitive to changes in surface mass balance and in flow rate factor. These results suggest that the climate variability of this region plays an important role on the glacier's dynamics, and that measurements of englacial temperature will improve the reliability of future modeling efforts. Our model shows that the position of the ice front exerts a strong control on the glacier flux. In our time-dependent simulation, the impacts of the observed front retreat on the glacier's dynamics persist beyond the present date. This suggests that Lange is likely still adjusting to past perturbations at its terminus.