GROUNDWATER-FLOW BENEATH ICE SHEETS .1. LARGE-SCALE PATTERNS

Ice sheets melting basally will inject water into subglacial permeable beds under a maximum head equivalent to the total ice pressure. Melting beneath the European Tee Sheet is simulated for the last two glacial cycles and the consequences for groundwater flow computed along an ice sheet flowline stretching from the low permeability basement rocks of Sweden to the thick Mesozoic and Cenozoic aquifers of The Netherlands and Germany. It is concluded: (i) that these large aquifers had a sufficient transmissivity to drain all subglacial meltwater; (ii) that groundwater heads, potential gradients and fluxes during glacial periods were very much larger than during interglacials; (iii) that proglacial permafrost played an important role in sustaining fluid overpressures in the ice sheet terminal zone; (iv) that during glacial periods major pressure pulses were driven through aquifer systems; and (v) that groundwater systems were completely reorganised.