Assessing the sensitivity of the Vanderford Glacier, East Antarctica, to basal melt and calving

Abstract. Vanderford Glacier is the fastest retreating glacier in East Antarctica; however, the dominant driver of the observed grounding line retreat remains largely unknown. The presence of warm modified Circumpolar Deep Water offshore Vanderford Glacier suggests that grounding line retreat may be driven by ice shelf basal melt, similar to the neighbouring Totten Glacier. Here, we use an ice sheet model to assess the relative contributions of basal melt and calving to mass loss and grounding line retreat at Vanderford Glacier. We compare simulations forced both by satellite-derived estimates of basal melt and calving, and varying magnitude idealised basal melt and ice-front retreat. Observed basal melt rates are too low to drive grounding line migration; instead, basal melt rates in excess of 50 m yr⁻¹ at the grounding line are required to generate grounding line retreat similar to observations. By contrast, calving experiments suggest that > 80 % ice-front retreat – well in excess of the observed ice-front retreat since 1996 – needs to occur to generate grounding line retreat similar to observations. Our results suggest that grounding line retreat and dynamic mass loss at Vanderford Glacier is likely to be dominated by basal melt, with an almost negligible contribution from calving. However, basal melt rates that generate grounding line retreat in our idealised experiments are twice the current estimates, highlighting the need for improved constraints on basal melting in the Vincennes Bay region.