Seismic evidence of widespread sediments beneath the Greenland Ice Sheet

Abstract Ice loss from the Greenland Ice Sheet contributes significantly to global sea-level rise; however, its magnitude and sensitivity to future climate change remain uncertain in large part due to questions regarding how basal processes influence ice-sheet dynamics. Specifically, the role of subglacial sediments in regulating Greenland Ice Sheet dynamics is not well understood. Thawed and saturated subglacial sediments enhance ice-sheet basal sliding, making it essential to quantify their distribution and properties beneath the Greenland Ice Sheet. Here, we apply high-frequency receiver function (RF) analysis to investigate subglacial sediments using seismic data collected across the Greenland Ice Sheet over recent decades. We find that the observed RFs consistently exhibit arrival-time delays relative to synthetic predictions from ice–over–hard bed models, indicating widespread low-velocity layers at the ice-bed interface. This low-velocity layer can be best explained by subglacial sediments with thicknesses up to ~200 m. The mapped results suggest that deformable sediments are more extensive than previously recognized but are distributed heterogeneously in space. Sediment thickness broadly correlates with modeled basal thermal state, with thicker and weaker sediments generally found beneath thawed regions. The presence of such sediments—even beneath regions not currently undergoing basal thaw—may precondition parts of the Greenland Ice Sheet for future dynamic change. Our findings highlight the importance of incorporating subglacial sediment properties into projections of ice-sheet behavior under a warming climate.