Models of ice-sheet hydrogeologic interactions: a review

This study reviews the state‐of‐the‐art and promising pathways to advance hydrologic models of groundwater flow systems and related transport processes in response to transient glacial loading. We also discuss the utility of hydrologic and geochemical data sets as a means of providing ground truth for these models. The paleohydrologic models presented herein should be used as analogues to assess high‐level nuclear waste repository stability in response to future episodes of glaciations in countries such as Canada, Sweden, and Switzerland. The next generation of fully coupled ice‐sheet‐aquifer models may also be of use in assessing rates of ice sheet denudation on Greenland and Antarctica in response to global warming. However, significant uncertainty exists in paleoclimatic forcing, paleohydrologic boundary conditions, and effective basin‐scale petrophysical parameters. Thus, model results must be viewed with some caution. Model results from studies reviewed herein suggest that during the last glacial maximum, recharge rates across glaciated basin margins increased by as much as 2–6 times modern levels. Paleohydrologic models predict that as ice sheets overran sedimentary basin margins, glacial melt water penetrated to depths of up to hundreds of meters. Recent ice‐sheet models that incorporated the effects of groundwater flow suggest that the presence of a 1–10 mm film of water at the glacial bed can increase basal ice sliding rates by up to 4 orders of magnitude. No firm theoretical basis exists for coupling ice sheet and subsurface hydrogeologic models nor the effects of permafrost on hydraulic conductivity. These issues could be resolved, to some degree, by additional careful experimental studies. Analysis of fluid pressures and flow rates beneath modern ice sheets using geochemical tracers would help to reduce the uncertainty regarding suitable hydrogeologic boundary conditions, parameterization of poromechanical coupling, and transport processes. Glacial geologists should work closely with modelers to provide better constraints on model boundary conditions.