The impact of geothermal heat flux on the last Scandinavian ice sheet over W Poland and E Germany

Abstract

ABSTRACT Geothermal heat flux (GHF) is heat supplied to the base of the ice sheet. It plays an important role in controlling ice sheet stability and affects basal temperatures, melting, and ice flow velocities. Here, we presume that the high GHF, as high as c. 110 mW m−2 over W Poland and more than 90 mW m−2 over E Germany, might have been one of the factors influencing the last Scandinavian ice sheet behaviour. For the analysed case, a GHF of 80 mW m−2 is more or less at the level of upward heat conduction. The difference in basal temperatures between areas with higher and lower GHF due to ice insulation was about 3–4oC. The minimum heat flow needed to reach the pressure melting point for the SIS beneath the ice streams in central west Poland was about 60 mW m−2. Possible interpretations would be that any excesses of heat participated in the meltwater production (by over 8 mm) that was at least partly stored subglacially due to the low-permeable bed and lack of channelised drainage traces, and maintained a fast ice streaming or enable reaching the pressure melting point or higher temperatures could counteract the freezing present near the ice sheet margin. The fast ice flow over central west Poland is confirmed by sedimentary and geomorphological evidence (e.g. mega-scale glacial lineations).