Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion
Subglacial water influences the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude, hence liquid water can be inferred from electrical resistivity depth profiles. Such pr...
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ftcopernicus:oai:publications.copernicus.org:sed78911 2023-05-15T16:37:51+02:00 Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion Killingbeck, Siobhan F. Booth, Adam D. Livermore, Philip W. Bates, Charles R. West, Landis J. 2019-08-06 application/pdf https://doi.org/10.5194/se-2019-126 https://www.solid-earth-discuss.net/se-2019-126/ eng eng doi:10.5194/se-2019-126 https://www.solid-earth-discuss.net/se-2019-126/ eISSN: 1869-9529 Text 2019 ftcopernicus https://doi.org/10.5194/se-2019-126 2019-12-24T09:48:44Z Subglacial water influences the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude, hence liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of time domain electromagnetics (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (<q>MuLTI</q>) to the inversion of TEM data constrained by independent depth constraints, to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier Midtdalsbreen, with depth constraints provided by co-located ground penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 10 2 Ωm ± 100 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (10 0 Ωm ± 15 %). High resistivity material, 5 × 10 4 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydro-geological interpretation of the subsurface, we propose a new 3D interpretation of the Midtdalsbreen subglacial material partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water. Text Ice permafrost Copernicus Publications: E-Journals |
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Copernicus Publications: E-Journals |
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English |
description |
Subglacial water influences the dynamics of ice masses. The state of subglacial pore water, whether liquid or frozen, is associated with differences in electrical resistivity that span several orders of magnitude, hence liquid water can be inferred from electrical resistivity depth profiles. Such profiles can be obtained from inversions of time domain electromagnetics (TEM) soundings, but these are often non-unique. Here, we adapt an existing Bayesian transdimensional algorithm (<q>MuLTI</q>) to the inversion of TEM data constrained by independent depth constraints, to provide statistical properties and uncertainty analysis of the resistivity profile with depth. The method was applied to ground-based TEM data acquired on the terminus of the Norwegian glacier Midtdalsbreen, with depth constraints provided by co-located ground penetrating radar data. Our inversion shows that the glacier bed is directly underlain by material of resistivity 10 2 Ωm ± 100 %, with thickness 5–40 m, in turn underlain by a highly conductive basement (10 0 Ωm ± 15 %). High resistivity material, 5 × 10 4 Ωm ± 25 %, exists at the front of the glacier. All uncertainties are defined by the interquartile range of the posterior resistivity distribution. Combining these resistivity profiles with co-located seismic shear-wave velocity inversions to further reduce ambiguity in the hydro-geological interpretation of the subsurface, we propose a new 3D interpretation of the Midtdalsbreen subglacial material partitioned into partially frozen sediment, frozen sediment/permafrost and weathered/fractured bedrock with saline water. |
format |
Text |
author |
Killingbeck, Siobhan F. Booth, Adam D. Livermore, Philip W. Bates, Charles R. West, Landis J. |
spellingShingle |
Killingbeck, Siobhan F. Booth, Adam D. Livermore, Philip W. Bates, Charles R. West, Landis J. Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
author_facet |
Killingbeck, Siobhan F. Booth, Adam D. Livermore, Philip W. Bates, Charles R. West, Landis J. |
author_sort |
Killingbeck, Siobhan F. |
title |
Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
title_short |
Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
title_full |
Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
title_fullStr |
Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
title_full_unstemmed |
Characterisation of subglacial water using a constrained transdimensional Bayesian Time Domain Electromagnetic Inversion |
title_sort |
characterisation of subglacial water using a constrained transdimensional bayesian time domain electromagnetic inversion |
publishDate |
2019 |
url |
https://doi.org/10.5194/se-2019-126 https://www.solid-earth-discuss.net/se-2019-126/ |
genre |
Ice permafrost |
genre_facet |
Ice permafrost |
op_source |
eISSN: 1869-9529 |
op_relation |
doi:10.5194/se-2019-126 https://www.solid-earth-discuss.net/se-2019-126/ |
op_doi |
https://doi.org/10.5194/se-2019-126 |
_version_ |
1766028154785234944 |