Fig. 1. Subglacial elevations of the bed beneath the Thwaites Glacier, West Antarctica, covering the area shown in red in the inset map in lower left. North is to the left. The thick black line at center left of the main image indicates the present-day ice shelf front. The dark blue colors indicate the presence of a remarkably deep, marine-based ice sheet, reaching from the ocean to far inland. Credit: Modified from Joughin et al. [2014]. Used with permission.