Geothermal heat flux is an important control on the dynamics of glaciers and ice sheets. In Greenland however, only few direct observations of geothermal heat flux exist. The exact spatial distribution and magnitude of heat flux in Greenland is therefore largely unknown. Many studies have attempted to constrain heat flux in Greenland indirectly by modelling it based on other observable variables, such as the seismic and magnetic structure of the Greenland lithosphere, or through techniques that extrapolate the existing measurements onto models of the Greenland lithology. Various estimates of Greenand heat flux have been produced this way, however many do not agree well with each other and show large inter- estimate variability both in terms of magnitude and spatial distribution of estimated heat flux values. Stable isotope composition of basal meltwater has previously not been considered in efforts to constrain Greenland geothermal heat flux. The ice layers in the Greenland ice sheet show large differences in δ18O values resulting from changes in climate throughout their deposi- tional history. If different ice layers are in contact with the bed, then spatial differences in geothermal heat flux will affect the local meltrates these layers experience at the ice sheet base and hence modulate the amount of meltwater each layer contributes into the subglacial drainaige system. If the δ18O values of the melting ice layers are sufficiently different, the isotopic composition of the mixed meltwater that flows through the subglacial hydrological system will be different for different spatial distributions of geothermal heat flux. By simulating the basal meltwater production in Greenland based on different published estimates of Greenland geothermal heat flux, I show in this thesis that different heat fluxes result in differences in the age distribution of the basal ice. In particular, the presence and extent of Eemian ice in central northern Greenland shows substantial differences for different heat flux estimates. As Eemian ice, being interglacial ice, shows higher δ18O val- ues than ice from the last glacial period, the modelled differences in Eemian extent result in detectable differences in the isotopic composition of the basal meltwater in North-east Greenland on the order of few permille. Stable isotope composition of basal meltwater might thus have the potential to contribute to the discussion about a heat flux hotspot in central northern Greenland.Master's Thesis in Earth ScienceGEOV399MAMN-GEO
