The extent of the West Antarctic Rift System into the Amundsen Sea Embayment: New indications by Curie depth estimates and geothermal gradients

The West Antarctic Rift System (WARS) provides a key component to Antarctica's tectonic evolution. The system's expansion is thought to progress from the Ross Sea to the Bellingshausen Sea and Amundsen Sea, where smaller rift arms seem to spread more diffusely. The rift troughs provide pathways for major ice streams, thus, their dynamics might directly be coupled to tectonic-morphological constraints. To-gether with regional crustal uplift (e.g. Marie Byrd Land), a common process in conti-nental rift systems, this has widely shaped the West Antarctic landscape during the Neogene. In the Amundsen Sea Embayment (ASE), a key sector of the West Antarctic Ice Sheet (WAIS), rapid changes have occurred over recent decades. The adjacent Pine Island Glacier and Thwaites Glacier, two outlets from a large drainage basin in the centre of the WAIS, exhibit highest increase in flow velocity in all of Antarctica. A large fraction of the WAIS is discharged into the embayment here. However, various models have been developed on the crustal architecture and tectonic history of this region, based on recent geophysical surveys, but any possible WARS activity re-mains uncertain. To investigate the possible effects of rifting history from the WARS on the ASE ice sheet dynamics, we use Curie Point Depth (CPD) estimates. They are based on air-borne-magnetic anomaly data and provide an additional insight into the deeper cru-stal properties. The CPD estimates image the depth of the deepest magnetic layer, hence the bottom depth of the igneous crust. For our estimates we assume a Curie temperature of 580°C at this depth. The well-established centroid method is used to calculate 30 CPDs in area windows of 200 x 200 km each with 50% overlapping the magnetic anomaly grid. We find that shallow CPDs and, therefore, higher geothermal gradients coincide with the location of previously postulated rift arms on the ASE shelf. Our in-situ tempera-ture measurements and derived geothermal heat flow provide a further geophysical data-set to investigate the extend of any crustal thinning and possible rift arms into the Amundsen Sea Embayment. The crustal thickness is an important contributor to the observed regional-scale geothermal heat flux variations and provides a geo-physical proxy for thermal status of crust and upper mantle