Geothermal Heat Flow in the Amundsen Sea Sector of West Antarctica

Abstract

The ice sheet inWest Antarctica is underlain by theWest Antarctic Rift System, which yields critical geological boundary conditions. The bedrock geology and the crustal structure of the rift system may influence the dynamics of the overlying glaciers, which in turn affect the stability of the ice sheet. Previous geophysical surveys have traced the West Antarctic Rift System from the Ross Sea to the Bellingshausen Sea and compared it to other major continental rift zones, such as the East African Rift System or the Basin and Range Province. While the rift system in the Ross Sea sector is relatively well understood, the remaining part of the rift system surrounds a higher degree of uncertainty. Young, continental rift systems, such as the West Antarctic Rift System, are associated with high geothermal heat flow and elevated lithospheric geotherms. In-situ temperature observations of geothermal heat flow are extremely sparse in Antarctica, but present crucial thermal boundary conditions ice sheet models and related sea level rise predictions. Moreover, temperature measurements are urgently required to study geodynamic and tectonic processes, subglacial lakes, hydrologic networks and ecosystems beneath ice sheets, that remain largely unexplored. Indirect methods, that estimate geothermal heat flow on regional to continental scales show poor correlation, which leads to ambiguous results in e.g. ice sheet models. Scientifically, this project aims at contributing to the overall knowledge of the thermal state of the crust in the Amundsen Sea Sector. Within the context of this thesis, a novel suit of in-situ temperature measurements were collected in the Amundsen Sea Embayment during RV Polarstern expedition PS75 (2010) and PS104 (2017). A novel magnetic anomaly grid is further presented, which includes aeromagnetic data collected during RV Polarstern expedition PS104, as well as previous aeromagnetic surveys, and forms the base for investigations of the thermal state of the crust. By Curie depth estimates, based on spectral analysis of the magnetic anomaly data and numerical models in 2D and 3D, the spatial distribution of geothermal heat flow and the thermal architecture of the crust is examined. The main outcomes of the thesis are local estimates of geothermal heat flow of 60 mWm2 to 90 mWm2, which is likely biased towards higher values due to the temperature variability in the water column. Indirect estimates from numerical models in contrast point towards elevated ( 90 mWm2) and locally high ( 90 mWm2) geothermal heat flow. In summary, the findings from the current thesis represent a significant advancement towards understanding of geothermal heat flow in the Amundsen Sea Sector of West Antarctica.