Abstract:

Water at the base of ice sheets modulates ice flow to the ocean by altering effective pressure and friction at the ice-bed interface. Understanding where this basal water comes from, how it reaches the bed, and how it affects ice flow is critical to predicting long-term ice-sheet evolution and sea-level rise under a warming climate. In this seminar, we will explore two different contributors to the subglacial water budget: Surface meltwater stored in supraglacial lakes and groundwater stored in subglacial sedimentary basins. We first use GNSS measurements on the Greenland Ice Sheet to show that stress interactions between nearby supraglacial lakes and moulins can trigger hydro-fracture in lake basins, establishing new pathways for meltwater to reach the bed. We then use idealized sedimentary basin models subjected to ice-sheet unloading to demonstrate that whether and how groundwater affects the ice-bed interface depends on the type of subglacial drainage system, ice-thinning distribution, and basin properties. Together, our findings underscore the need to incorporate interactions across supraglacial, subglacial, and subsurface hydrologic systems into large-scale prognostic ice-sheet models.