Basal thermal state of the Greenland Ice Sheet

Abstract

Understanding the basal thermal state of the Greenland Ice Sheet (GrIS) has important implications for modeling its ongoing contribution to global sea level. Apart from removing paleoclimate information from basal layers, basal melt affects the friction at the ice-bedrock interface which has important consequences in terms of ice discharge to the surrounding oceans. The basal thermal state of the GrIS, however, is poorly constrained by observations. The paucity of information is mostly due to expensive and logistically complicated deep-ice drilling campaigns. As a result, only a handful of deep ice cores are available in the entire GrIS. Because of the significance of the basal thermal condition of the GrIS and the difficulties associated with obtaining direct observations from the bed, there is a need for reliable numerical modeling studies, as well as remote sensing techniques. Perhaps the most important, yet least-known, thermal boundary condition for modeling the basal temperature of the GrIS is the spatial distribution of geothermal heat flux (GHF) beneath the ice. Several models have aimed at estimating the GHF distribution in Greenland. However, the majority of these GHF models sharply contradict each other and cannot reproduce the temperature measurements at ice cores, when implemented in numerical ice sheet models. This research improves our understanding of the basal thermal condition of the GrIS from three perspectives. First, it reveals the shortcomings of an analytical temperature solution for ice sheets that has been frequently used since the 1950s, and proposes a new solution to resolve the old solution’s shortcomings. Second, in contrast with other GHF maps, this study derives a new GHF map for Greenland that honors geologic and geophysical properties, as well as ice core information. And finally, this study aims at reconciling remotely-sensed observations of basal water with the current GHF models in Greenland.