Quantifying 3D topographic effects on geothermal heat flow beneath the Northeast Greenland Ice Stream

Abstract. The North East Greenland Ice Stream (NEGIS) is the largest ice stream in Greenland, and previous studies debate the reasons for its initiation so far into the interior of the ice sheet. Here, we explore how important 3D geothermal heat flow (GHF) is to effective heat transport as a contributing factor. We estimate the effect of high-resolution bed topography on GHF using the finite-element framework pyGIMLi to perform 3D thermal simulations. The bed topography is derived from recent airborne ice-penetrating radar data and covers an area of approximately 40 x 60 km² surrounding the EastGRIP ice core site at the onset of the ice stream. As large-scale GHF models currently show substantial discrepancies in north-east Greenland, we evaluate the 3D effects for two contrasting background GHF models. Our results show that incorporation of high-resolution bed topography leads to local GHF deviations of up to 20 % relative to background models, closely following topographic patterns. Therefore, incorporating high-resolution GHF, especially in regions with a large ice flux, could reduce uncertainties in our understanding of the origin and stability of ice streams. However, for the NEGIS itself, our preferred background model of low GHF implies that topographic effects channeling GHF do not significantly alter the behavior of the ice stream.