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 driver of observed grounding line retreat remains unknown. The presence of warm modified Circumpolar Deep Water offshore of Vanderford Glacier suggests that grounding line retreat may be driven by sub-ice-shelf basal melt, similar to the neighbouring Totten Glacier. We use an ice sheet model to assess the sensitivity of mass loss and grounding line retreat at Vanderford Glacier to sub-ice-shelf basal melt and ice front retreat. We compare simulations forced by satellite-derived estimates of long-term mean annual basal melt and observed annual ice front retreat, as well as varying magnitudes of idealised basal melt and ice front retreat. Forcing the model with satellite-derived basal melt rates and observed ice front retreat results in minimal grounding line retreat, suggesting that these forcings cannot generate grounding line retreat of a similar magnitude to observations and that observed ice front retreat has removed only passive ice from the ice shelf. In our sensitivity experiments, ice front retreat > 80 % of the ice shelf length fails to produce grounding line retreat of a similar magnitude to observations. Instead, basal melt rates > 50 m yr-1 at the grounding line - more than twice current estimates - are needed. Our results suggest that grounding line retreat and dynamic mass loss at Vanderford Glacier is likely to be dominated by basal melting higher than current satellite-derived estimates, highlighting the need for improved constraints on basal melt estimates in the Vincennes Bay region, and that ice front retreat has an almost negligible impact on sustained grounding line retreat.