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. Melti ng beneath the European Tee Sheet is simulated for the last two glacia l cycles and the consequences for groundwater flow computed along an i ce sheet flowline stretching from the low permeability basement rocks of Sweden to the thick Mesozoic and Cenozoic aquifers of The Netherlan ds and Germany. It is concluded: (i) that these large aquifers had a s ufficient transmissivity to drain all subglacial meltwater; (ii) that groundwater heads, potential gradients and fluxes during glacial perio ds were very much larger than during interglacials; (iii) that proglac ial permafrost played an important role in sustaining fluid overpressu res in the ice sheet terminal zone; (iv) that during glacial periods m ajor pressure pulses were driven through aquifer systems; and (v) that groundwater systems were completely reorganised.