Sediment deposition at the modern grounding zone of Whillans Ice Stream, West Antarctica

Much of the threshold behavior of marine ice sheets is thought to result from processes occurring at the grounding zone, where the ice sheet transitions into the ice shelf. At short timescales (decades to centuries), grounding zone behavior is likely to be influenced by ongoing sediment deposition, which can stabilize the grounding zone position. We present a ground-based geophysical study across the modern grounding zone of Whillans Ice Stream. Within an embayment setting, where subglacial meltwater drains, we image sedimentary deposits; however, we do not observe the classic asymmetric grounding zone wedge deposits, which are found in the paleorecord and are thought to stabilize the grounding zone position. At an adjacent peninsula, we image the grounding zone and an ice-shelf pinning point and again observe no wedge deposits.