Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics
Predictions of ice-sheet mass loss, and therefore predictions of global sea level rise, depend sensitively upon how ice-sheet motion is incorporated into numerical models. Using field observations and numerical modelling, this thesis demonstrates that two frequently overlooked processes are central...
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University of Cambridge
2022
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ftunivcam:oai:www.repository.cam.ac.uk:1810/343281 2024-01-21T10:01:49+01:00 Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics Law, Robert 2022-11-05T15:59:06Z application/pdf https://www.repository.cam.ac.uk/handle/1810/343281 https://doi.org/10.17863/CAM.90692 eng eng University of Cambridge https://doi.org/10.17863/CAM.65812 https://www.repository.cam.ac.uk/handle/1810/343281 doi:10.17863/CAM.90692 Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/ Antarctic Ice Sheet Fibre-optics Finite Element Modelling Glacier borehole Glacier fieldwork Glaciology Greenland Ice Sheet Thesis Doctoral Doctor of Philosophy (PhD) 2022 ftunivcam https://doi.org/10.17863/CAM.9069210.17863/CAM.65812 2023-12-28T23:23:16Z Predictions of ice-sheet mass loss, and therefore predictions of global sea level rise, depend sensitively upon how ice-sheet motion is incorporated into numerical models. Using field observations and numerical modelling, this thesis demonstrates that two frequently overlooked processes are central to describing borehole observations of fast ice-sheet motion --- intermediate-scale (<25 m, ⪅2 km) interaction of ice motion with realistic or real bed topography, and modulation of these ice-motion patterns through a basal layer of temperate ice (much softer ice at the pressure-melting point). I first present a fibre-optic data set from a 1,043 m deep borehole drilled to the base of the fast-moving (>500 m a‾¹) marine-terminating Sermeq Kujalleq (Store Glacier) at the western margin of the Greenland Ice Sheet. This reveals hitherto unappreciated complexity in the processes behind fast ice-sheet motion. I observe substantial but isolated strain heating ~220 m beneath the surface within stiffer interglacial-phase ice where previously none was expected. Ice deformation within glacial-phase ice below 889 m is further observed to be strongly heterogeneous, with a possible high-strain interface demarcating the Last Glacial-Interglacial Transition. I also find a 73-m-thick temperate basal layer, notably thicker than the <10-m-thick temperate layer just 8.9 km away, unexplained by existing theory, and interpreted to be important for the glacier's fast motion. To disentangle this observed complexity, I then model three isolated 3D domains from the Greenland Ice Sheet's western margin --- two from Sermeq Kujalleq and one from the land-terminating Isunnguata Sermia, all centred above a central borehole observation. By incorporating high-resolution realistic geostatistically simulated topography, I demonstrate that a layer of basal temperate ice with spatially highly variable thickness forms naturally in both marine- and land-terminating settings, alongside ice-motion patterns which are far more complex than previously ... Doctoral or Postdoctoral Thesis Antarc* Antarctic glacier Greenland Ice Sheet Kujalleq Sermeq Kujalleq Apollo - University of Cambridge Repository Antarctic Greenland Kujalleq ENVELOPE(-46.037,-46.037,60.719,60.719) Isunnguata Sermia ENVELOPE(-50.167,-50.167,67.183,67.183) |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
Antarctic Ice Sheet Fibre-optics Finite Element Modelling Glacier borehole Glacier fieldwork Glaciology Greenland Ice Sheet |
spellingShingle |
Antarctic Ice Sheet Fibre-optics Finite Element Modelling Glacier borehole Glacier fieldwork Glaciology Greenland Ice Sheet Law, Robert Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
topic_facet |
Antarctic Ice Sheet Fibre-optics Finite Element Modelling Glacier borehole Glacier fieldwork Glaciology Greenland Ice Sheet |
description |
Predictions of ice-sheet mass loss, and therefore predictions of global sea level rise, depend sensitively upon how ice-sheet motion is incorporated into numerical models. Using field observations and numerical modelling, this thesis demonstrates that two frequently overlooked processes are central to describing borehole observations of fast ice-sheet motion --- intermediate-scale (<25 m, ⪅2 km) interaction of ice motion with realistic or real bed topography, and modulation of these ice-motion patterns through a basal layer of temperate ice (much softer ice at the pressure-melting point). I first present a fibre-optic data set from a 1,043 m deep borehole drilled to the base of the fast-moving (>500 m a‾¹) marine-terminating Sermeq Kujalleq (Store Glacier) at the western margin of the Greenland Ice Sheet. This reveals hitherto unappreciated complexity in the processes behind fast ice-sheet motion. I observe substantial but isolated strain heating ~220 m beneath the surface within stiffer interglacial-phase ice where previously none was expected. Ice deformation within glacial-phase ice below 889 m is further observed to be strongly heterogeneous, with a possible high-strain interface demarcating the Last Glacial-Interglacial Transition. I also find a 73-m-thick temperate basal layer, notably thicker than the <10-m-thick temperate layer just 8.9 km away, unexplained by existing theory, and interpreted to be important for the glacier's fast motion. To disentangle this observed complexity, I then model three isolated 3D domains from the Greenland Ice Sheet's western margin --- two from Sermeq Kujalleq and one from the land-terminating Isunnguata Sermia, all centred above a central borehole observation. By incorporating high-resolution realistic geostatistically simulated topography, I demonstrate that a layer of basal temperate ice with spatially highly variable thickness forms naturally in both marine- and land-terminating settings, alongside ice-motion patterns which are far more complex than previously ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Law, Robert |
author_facet |
Law, Robert |
author_sort |
Law, Robert |
title |
Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
title_short |
Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
title_full |
Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
title_fullStr |
Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
title_full_unstemmed |
Fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
title_sort |
fibre-optic borehole observations and numerical modelling of complex ice-sheet thermodynamics |
publisher |
University of Cambridge |
publishDate |
2022 |
url |
https://www.repository.cam.ac.uk/handle/1810/343281 https://doi.org/10.17863/CAM.90692 |
long_lat |
ENVELOPE(-46.037,-46.037,60.719,60.719) ENVELOPE(-50.167,-50.167,67.183,67.183) |
geographic |
Antarctic Greenland Kujalleq Isunnguata Sermia |
geographic_facet |
Antarctic Greenland Kujalleq Isunnguata Sermia |
genre |
Antarc* Antarctic glacier Greenland Ice Sheet Kujalleq Sermeq Kujalleq |
genre_facet |
Antarc* Antarctic glacier Greenland Ice Sheet Kujalleq Sermeq Kujalleq |
op_relation |
https://doi.org/10.17863/CAM.65812 https://www.repository.cam.ac.uk/handle/1810/343281 doi:10.17863/CAM.90692 |
op_rights |
Attribution 4.0 International (CC BY 4.0) https://creativecommons.org/licenses/by/4.0/ |
op_doi |
https://doi.org/10.17863/CAM.9069210.17863/CAM.65812 |
_version_ |
1788692002759507968 |