At the Last Glacial Maximum (LGM), the Rhine Glacier complex (Rhine and Linth
glaciers) formed large piedmont lobes extending north into the Swiss and
German Alpine forelands. Numerous overdeepened valleys there were formed by
repeated glaciations. A characteristic of these overdeepened valleys is their location close to the LGM ice margin, away from the Alps. Numerical models of ice flow of the Rhine Glacier indicate a poor fit between the sliding distance, a proxy for glacial erosion, and the location
of these overdeepenings. Calculations of the hydraulic potential based on
the computed time-dependent ice surface elevations of the Rhine Glacier lobe obtained from a high-resolution thermo-mechanically coupled Stokes flow model are used to estimate the location of subglacial water drainage routes. Results indicate that the subglacial water discharge is high and focused along glacial valleys and overdeepenings when water pressure is equal to the ice overburden pressure. These conditions are necessary for subglacial water to remove basal sediments, expose fresh bedrock, and favor further erosion by quarrying and abrasion. Knowledge of the location of paleo-subglacial water drainage routes may be useful to understand patterns of subglacial erosion beneath paleo-ice masses that do not otherwise relate to the sliding of ice. Comparison of the erosion pattern from
subglacial meltwater with those from quarrying and abrasion shows the
importance of subglacial water flow in the formation of distal
overdeepenings in the Swiss lowlands.</p
