The impact of glaciations and glacial processes on groundwater flow dynamics: a numerical investigation
Abstract:Numerical models are widely used to investigate the impact of glaciations on groundwater flow systems because they can simulate complex glacial processes. However, it isn’t clear which of these processes are relevant to adequately capture groundwater flow dynamics. Given the complexity of representing these processes in a numerical model and the paucity of field data available for their validation, it is of prime interest to assess how they impact groundwater flow and if any of these processes could be neglected.
In order to assess the specific impact of glacial processes on groundwater flow dynamics, those processes were included in the numerical model FEFLOW and simulations were conducted in a simple conceptual model representing a 21 ky glacial cycle in a sedimentary basin. The following processes have been simulated: subglacial recharge, linear and non-linear compaction of the porous medium under the weight of the ice, isostasy, proglacial lakes, as well as permafrost. Solute transport was simulated along with groundwater flow to track groundwater originating from the ice-sheet. To interpret the results, a base case scenario considering only subglacial recharge was selected and compared with the other scenarios, where individual glacial processes were simulated.
When comparing the results at the end of the simulations, it appears that most of the aforementioned glacial processes don’t lead to a significant difference in meltwater distribution with respect to the base case. Only hydromechanical coupling brings some noticeable change. Conversely, the type and the value of the boundary condition applied at the base of the ice-sheet play a major role in groundwater flow dynamics. The presence of confining hydrogeological units also seems to be a key to understand the long-term effect of glaciations. These results suggest that some of the glacial processes may be neglected for the simulation of groundwater flow dynamics during a glacial period.