Modelling the hydrology of sedimentary basins beneath marine ice sheets

The flow of Antarctic ice streams is modulated by a subglacial hydrological system, including “shallow” water transported through till and channels as well as “deep” groundwater stored in sedimentary basins. The latter has risen to prominence in recent years as a contributor to subglacial hydrology through the exchange of groundwater with the “shallow” system. These sedimentary basins possess complex geometries and display variations in salinity due to historic seawater intrusion. However, relatively little is known about the hydraulic properties of subglacial sedimentary basins, or their overall contribution to subglacial hydrology. To address these questions, we develop a mathematical model of groundwater flow in a sedimentary basin driven by an overlying marine ice sheet over geological timescales. By comparing modelled seawater intrusion to field observations of groundwater salinity, we  estimate the permeability of sedimentary basins in West Antarctica. We also show that exchange of groundwater between sedimentary basins and the shallow hydrological system is primarily driven by spatial variation in the basin geometry, and discuss implications for the dynamics of the ice stream.