Abstract
The specific impact of glacial processes on groundwater flow and solute transport under ice-sheets was determined by means of numerical simulations. Groundwater flow and the transport of δ18O, TDS, and groundwater age were simulated in a generic sedimentary basin during a single glacial event followed by a postglacial period. Results show that simulating subglacial recharge with a fixed flux boundary condition is relevant only for small fluxes, which could be the case under partially wet-based ice-sheets. Glacial loading decreases overpressures, which appear only in thick and low hydraulic diffusivity layers. If subglacial recharge is low, glacial loading can lead to underpressures after the retreat of the ice-sheet. Isostasy reduces considerably the infiltration of meltwater and the groundwater flow rates. Below permafrost, groundwater flow is reduced under the ice-sheet but is enhanced beyond the ice-sheet front. Accounting for salinity-dependent density reduces the infiltration of meltwater at depth. This study shows that each glacial process is potentially relevant in models of subglacial groundwater flow and solute transport. It provides a good basis for building and interpreting such models in the future.
Highlights
Glaciations are known to have a large and long-lasting impact on groundwater flow
A particular attention was given to simulated groundwater flow rates and meltwater volumes, which are shown on Figures 4 and 5
This study assessed the specific impact of glacial processes associated with wet-based ice-sheets that were simulated in previous hydrogeological modelling studies: subglacial recharge, direct glacial loading, isostasy, the presence of proglacial lake or sea, permafrost, and density-dependent mixing between meltwater and brines
Summary
Glaciations are known to have a large and long-lasting impact on groundwater flow. Several geochemical and isotopic studies have shown that water of glacial origin is still present in basins in North America (e.g., [1, 2]) and northern Europe [3] that were formerly covered by ice-sheets (see [4] for a review of these studies). Ice-sheets can be partially wet-based [6] due to basal friction and can release large volumes of subglacial meltwater. Grundl et al [9] showed that recharge of supraglacial meltwater can occur below ice-sheets due to the presence of crevasses. In this case, the pressure at the base of the ice-sheet would not be induced by the weight of the ice but by the weight of the column of water within the ice. The presence of fresh water at depth [2] or in abnormal position with respect to present-day hydraulic gradient [10] suggests that the trend and the intensity of regional flow were considerably modified. Modelling studies confirmed that the injection of large volumes of meltwater has the potential to reorganize entirely the pattern of regional flow [7] and even to reverse the direction of the flow if the ice-sheet runs opposite to the direction of interglacial topography-driven flow [11]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
