Project Details
Projekt
Geophysical characterization of the crust and subglacial sediments near the grounding zone of the Ekström Ice Shelf, East Antarctica, using Magnetotellurics (PRISTINE)
Subject Area
Geophysics
Term
since 2024
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 542003282
The characterization of the ice-sheet-shelf transition zone and the physical properties of subglacial rocks are key to understanding Antarctic ice sheet dynamics. Despite their importance, local constraints on the grounding zone and associated processes, such as cavity melting and characterization of subglacial rocks and sediments that control basal-drag ice flow remain scarce throughout Antarctica. To improve this situation, we propose to image the electrical conductivity of sediments and bedrock beneath the ice sheet using the Magnetotelluric (MT) method. MT measures the Earth’s response to natural time-varying electromagnetic fields to infer the distribution of electrical conductivity in the subsurface. The method is particularly suited to Antarctica since it has virtually no environmental footprint and does not require the generation or injection of man-made artificial signals. Motivated by this, a multi-method (MT+Seismology+GNSS) field experiment was conducted by AWI and GFZ during the 2022/2023 field seasons over the grounding zone of the Ekström Ice Shelf, East Antarctica, where ice streams feed the shelf. A total of 19 MT stations were deployed with an average spacing of 5 km, providing high quality data. This is the first MT dataset from the entire Queen Maud Land. However, modeling these data is very challenging. Extreme conductivity contrasts between seawater, ice and bedrock together with complex bedrock topography and bathymetry present insurmountable barriers to conventional numerical methods. In order to overcome these challenges, we rely on our novel finite element solver with adaptive local mesh refinement to construct the models. Preliminary 2D conductivity modeling clearly shows that the MT data are highly sensitive to the ocean-land contact, and a comparison between the measured data and the 2D model already shows remarkable similarities in the main trends and asymptotics. However, we also identify significant effects in the data that cannot be explained by 2D modeling and which are likely to be caused by yet unknown subglacial geologic structures and unmodelled 3-D bathymetric effects. Full exploitation of this new dataset therefore requires a dedicated 3D modeling and inversion study and systematic hypothesis testing. We also intend to improve aspects of the data processing, as the high-frequency MT data appear to be affected by the high contact resistances of the electrodes, and to investigate whether external source effects affect MT responses given the proximity of polar and auroral electrojets. Finally, we intend to reprocess existing seismic reflection data from this region which can then be integrated with the MT-based subsurface models.
DFG Programme
Infrastructure Priority Programmes
Subproject of
SPP 1158:
Infrastructure area - Antarctic Research with Comparative Investigations in Arctic Sea Ice Areas
International Connection
United Kingdom
Cooperation Partner
Professor Dr. Bernd Kulessa
