Upper mantle temperatures illuminate the Iceland hotspot track and understanding of ice–Earth interactions in Greenland

Abstract

The thermal structure of the Earth beneath Greenland reflects the tectonic history of the region and impacts ice sheet evolution due to surface heat flow and the influence of temperature on Earth rheology, and thus glacial isostatic adjustment. We present results from a probabilistic joint inversion of multiple satellite and land-based datasets to determine the thermal structure of the lithosphere and upper mantle beneath Greenland and consider the implications for our understanding of the tectonic history, isostatic deformation, and Greenland ice sheet evolution. Passage of Greenland over the Iceland hotspot is well known but there remains considerable debate on the trajectory of this path. Our findings reveal strong lateral variability in thermal structure that is consistent with reconstructions of a west-to-east hotspot track across central Greenland. Applying our temperature model to infer mechanical properties of the solid Earth reveals viscosity variations reaching 3 orders of magnitude in the upper mantle. We generate an ensemble of plausible 3D viscosity models and produce quality fits to both paleo sea level and contemporary vertical land motion datasets. This result supports the veracity of our temperature model and questions the need for a large component of transient deformation to explain the observations. Our regional temperature and viscosity models can be used to develop improved reconstructions and understanding of past Greenland ice sheet changes and explore the influence of 3D Earth structure on simulating ice sheet and sea level evolution in the past and future.