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Discussion papers
https://doi.org/10.5194/tc-2019-74
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/tc-2019-74
© Author(s) 2019. This work is distributed under
the Creative Commons Attribution 4.0 License.

Research article 30 Apr 2019

Research article | 30 Apr 2019

Review status
This discussion paper is a preprint. It is a manuscript under review for the journal The Cryosphere (TC).

Revisiting Austfonna, Svalbard with potential field methods – A new characterization of the bed topography and its physical properties

Marie-Andrée Dumais1,2 and Marco Brönner1,2 Marie-Andrée Dumais and Marco Brönner
  • 1Department of Geoscience and Petroleum, Norwegian University of Science and Technology, 7031 Trondheim, Norway
  • 2Geological Survey of Norway, 7040 Trondheim, Norway

Abstract. With hundreds of meters of ice, the bedrock underlying Austfonna, the largest ice cap on Svalbard, is hardly characterized in terms of topography and physical properties. Ground penetrating radar (GPR) measurements supply ice thickness estimation but the data quality is temperature-dependent, comprising uncertainties. To remedy this, we include airborne gravity measurements. With a significant density contrast between ice and bedrock, sub-glacial bed topography is effectively derived from gravity modeling. While the ice thickness model relies primarily on the gravity data, integrating airborne magnetic data provides an extra insight of the basement distribution. This contributes to refine the range of density expected under the ice and improve the sub-ice model. From this study, a prominent magmatic N-S oriented intrusion and the presence of carbonates are assessed. The results reveal the complexity of the sub-surface lithology characterized with different basement affinities. With the geophysical parameters of the bedrock determined, a new bed topography is extracted, adjusted for the potential field interpretation. When the results are compared to bed elevation maps previously produced by radio echo-sounding (RES) and GPR data, the discrepancies are pronounced where the RES and GPR data are scarce. Hence, areas with limited coverage are addressed with the potential field interpretation, increasing the accuracy of the overall bed topography. In addition, the methodology improves the understanding of the geology, assigns physical properties to the basements, and reveals the presence of softer bed, carbonates and magmatic intrusions under Austfonna which influence the basal sliding rates and surges.

Marie-Andrée Dumais and Marco Brönner
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Marie-Andrée Dumais and Marco Brönner
Marie-Andrée Dumais and Marco Brönner
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Short summary
The subglacial bed of Austfonna is investigated using potential field methods. Airborne gravity data provide a new bed topography improved from the traditional ground penetrating radar measurements. Combined with airborne magnetic data, a 2D-forward model reveals the heterogeneity of the sub-surface lithology, and the bed physical properties. Our approach also assesses the presence of softer bed, carbonates and magmatic intrusions under Austfonna which contribute to the subglacial processes.
The subglacial bed of Austfonna is investigated using potential field methods. Airborne gravity...
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