Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream
Ice streams are major contributors to ice sheet mass loss and sea level rise. Effects of their dynamic behaviour are imprinted into seismic properties, such as wave speeds and anisotropy. Here, we present results from a distributed acoustic sensing (DAS) experiment in a deep ice-core borehole in the...
Published in: | Geophysical Journal International |
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2023
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Online Access: | https://hal.science/hal-04357096 https://hal.science/hal-04357096/document https://hal.science/hal-04357096/file/islandora_168592.pdf https://doi.org/10.1093/gji/ggad344 |
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ftccsdartic:oai:HAL:hal-04357096v1 2024-02-11T10:01:42+01:00 Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream Fichtner, Andreas Hofstede, Coen Gebraad, Lars Zunino, Andrea Zigone, Dimitri Eisen, Olaf Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich) Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI) Helmholtz-Gemeinschaft = Helmholtz Association Institut Terre Environnement Strasbourg (ITES) École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) Universität Bremen 2023 https://hal.science/hal-04357096 https://hal.science/hal-04357096/document https://hal.science/hal-04357096/file/islandora_168592.pdf https://doi.org/10.1093/gji/ggad344 en eng HAL CCSD Oxford University Press (OUP) info:eu-repo/semantics/altIdentifier/doi/10.1093/gji/ggad344 hal-04357096 https://hal.science/hal-04357096 https://hal.science/hal-04357096/document https://hal.science/hal-04357096/file/islandora_168592.pdf doi:10.1093/gji/ggad344 info:eu-repo/semantics/OpenAccess ISSN: 0956-540X EISSN: 1365-246X Geophysical Journal International https://hal.science/hal-04357096 Geophysical Journal International, 2023, 235 (3), pp.2430-2441. ⟨10.1093/gji/ggad344⟩ Glaciology Arctic region Tomography Seismic anisotropy [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology info:eu-repo/semantics/article Journal articles 2023 ftccsdartic https://doi.org/10.1093/gji/ggad344 2024-01-20T23:48:39Z Ice streams are major contributors to ice sheet mass loss and sea level rise. Effects of their dynamic behaviour are imprinted into seismic properties, such as wave speeds and anisotropy. Here, we present results from a distributed acoustic sensing (DAS) experiment in a deep ice-core borehole in the onset region of the Northeast Greenland Ice Stream, with focus on phenomenological and methodological aspects. A series of active seismic surface sources produced clear recordings of the P and S wavefield, including internal reflections, along a 1500 m long fibre-optic cable that was placed into the borehole. The combination of nonlinear traveltime tomography with a firn model constrained by multimode surface wave data, allows us to invert for P and S wave speeds with depth-dependent uncertainties on the order of only 10 m s−1, and vertical resolution of 20–70 m. The wave speed model in conjunction with the regularly spaced DAS data enable a straightforward separation of internal upward reflections followed by a reverse-time migration that provides a detailed reflectivity image of the ice. While the differences between P and S wave speeds hint at anisotropy related to crystal orientation fabric, the reflectivity image seems to carry a pronounced climatic imprint caused by rapid variations in grain size. Further improvements in resolution do not seem to be limited by the DAS channel spacing. Instead, the maximum frequency of body waves below ∼200 Hz, low signal-to-noise ratio caused by poor coupling, and systematic errors produced by the ray approximation, appear to be the leading-order issues. Among these, only the latter has a simple existing solution in the form of full-waveform inversion. Improving signal bandwidth and quality, however, will likely require a significantly larger effort in terms of both sensing equipment and logistics. Article in Journal/Newspaper Arctic Greenland ice core Ice Sheet Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) Arctic Greenland Geophysical Journal International 235 3 2430 2441 |
institution |
Open Polar |
collection |
Archive ouverte HAL (Hyper Article en Ligne, CCSD - Centre pour la Communication Scientifique Directe) |
op_collection_id |
ftccsdartic |
language |
English |
topic |
Glaciology Arctic region Tomography Seismic anisotropy [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology |
spellingShingle |
Glaciology Arctic region Tomography Seismic anisotropy [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology Fichtner, Andreas Hofstede, Coen Gebraad, Lars Zunino, Andrea Zigone, Dimitri Eisen, Olaf Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
topic_facet |
Glaciology Arctic region Tomography Seismic anisotropy [SDU.STU.GL]Sciences of the Universe [physics]/Earth Sciences/Glaciology |
description |
Ice streams are major contributors to ice sheet mass loss and sea level rise. Effects of their dynamic behaviour are imprinted into seismic properties, such as wave speeds and anisotropy. Here, we present results from a distributed acoustic sensing (DAS) experiment in a deep ice-core borehole in the onset region of the Northeast Greenland Ice Stream, with focus on phenomenological and methodological aspects. A series of active seismic surface sources produced clear recordings of the P and S wavefield, including internal reflections, along a 1500 m long fibre-optic cable that was placed into the borehole. The combination of nonlinear traveltime tomography with a firn model constrained by multimode surface wave data, allows us to invert for P and S wave speeds with depth-dependent uncertainties on the order of only 10 m s−1, and vertical resolution of 20–70 m. The wave speed model in conjunction with the regularly spaced DAS data enable a straightforward separation of internal upward reflections followed by a reverse-time migration that provides a detailed reflectivity image of the ice. While the differences between P and S wave speeds hint at anisotropy related to crystal orientation fabric, the reflectivity image seems to carry a pronounced climatic imprint caused by rapid variations in grain size. Further improvements in resolution do not seem to be limited by the DAS channel spacing. Instead, the maximum frequency of body waves below ∼200 Hz, low signal-to-noise ratio caused by poor coupling, and systematic errors produced by the ray approximation, appear to be the leading-order issues. Among these, only the latter has a simple existing solution in the form of full-waveform inversion. Improving signal bandwidth and quality, however, will likely require a significantly larger effort in terms of both sensing equipment and logistics. |
author2 |
Eidgenössische Technische Hochschule - Swiss Federal Institute of Technology Zürich (ETH Zürich) Alfred-Wegener-Institut, Helmholtz-Zentrum für Polar- und Meeresforschung = Alfred Wegener Institute for Polar and Marine Research = Institut Alfred-Wegener pour la recherche polaire et marine (AWI) Helmholtz-Gemeinschaft = Helmholtz Association Institut Terre Environnement Strasbourg (ITES) École Nationale du Génie de l'Eau et de l'Environnement de Strasbourg (ENGEES)-Université de Strasbourg (UNISTRA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS) Universität Bremen |
format |
Article in Journal/Newspaper |
author |
Fichtner, Andreas Hofstede, Coen Gebraad, Lars Zunino, Andrea Zigone, Dimitri Eisen, Olaf |
author_facet |
Fichtner, Andreas Hofstede, Coen Gebraad, Lars Zunino, Andrea Zigone, Dimitri Eisen, Olaf |
author_sort |
Fichtner, Andreas |
title |
Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
title_short |
Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
title_full |
Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
title_fullStr |
Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
title_full_unstemmed |
Borehole fibre-optic seismology inside the Northeast Greenland Ice Stream |
title_sort |
borehole fibre-optic seismology inside the northeast greenland ice stream |
publisher |
HAL CCSD |
publishDate |
2023 |
url |
https://hal.science/hal-04357096 https://hal.science/hal-04357096/document https://hal.science/hal-04357096/file/islandora_168592.pdf https://doi.org/10.1093/gji/ggad344 |
geographic |
Arctic Greenland |
geographic_facet |
Arctic Greenland |
genre |
Arctic Greenland ice core Ice Sheet |
genre_facet |
Arctic Greenland ice core Ice Sheet |
op_source |
ISSN: 0956-540X EISSN: 1365-246X Geophysical Journal International https://hal.science/hal-04357096 Geophysical Journal International, 2023, 235 (3), pp.2430-2441. ⟨10.1093/gji/ggad344⟩ |
op_relation |
info:eu-repo/semantics/altIdentifier/doi/10.1093/gji/ggad344 hal-04357096 https://hal.science/hal-04357096 https://hal.science/hal-04357096/document https://hal.science/hal-04357096/file/islandora_168592.pdf doi:10.1093/gji/ggad344 |
op_rights |
info:eu-repo/semantics/OpenAccess |
op_doi |
https://doi.org/10.1093/gji/ggad344 |
container_title |
Geophysical Journal International |
container_volume |
235 |
container_issue |
3 |
container_start_page |
2430 |
op_container_end_page |
2441 |
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1790597506037448704 |