Basal channels, ice thinning and grounding zone retreat at Thwaites Glacier, West Antarctica

Abstract. Antarctic ice shelves buttress the flow of the ice sheet, tempering sea level rise, but they are vulnerable to basal melting from contact with the ocean, as well as mass loss due to fracture and calving. Melt channels and similar features at the bases of ice shelves have been linked to enhanced basal melting and observed to intersect the grounding line, where the greatest melt rates are often observed. The ice shelf of Thwaites Glacier is especially vulnerable to melt and subsequent retreat of the grounding line because the glacier has an inland–sloping bed leading to a deep trough below the grounded ice sheet. We use digital surface models from 2010–2022 to investigate the evolution of ice–shelf basal channels and a proxy for the grounding line on the Thwaites Glacier ice shelf. We find that the highest sustained rates of grounding–line retreat (up to 0.7 km a-1) are associated with high melt rates (up to ~250 m a-1) near the intersections of basal channels with the grounding zone, steep local retrograde slopes, and where subglacial channel discharge is expected. Detailed observations of basal channels collocated with regions of grounding–line retreat will further elucidate the complicated processes occurring at the ice–ocean interface and hopefully lead to more accurate estimates of current and future ice–shelf melting and evolution.