Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing
Research was funded by the UK Natural Environmental Research Council grants NE/L006707/1 and NE/L005409/1 and a HEFCW/Aberystwyth University Capital Equipment Grant to B.H. Data will be available via the project website (www.projectmidas.org) and the UK Polar Data Centre (https://www.bas.ac.uk/data/...
Published in: | Journal of Geophysical Research: Earth Surface |
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Online Access: | http://hdl.handle.net/10023/10881 https://doi.org/10.1002/2016JF004047 |
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/10881 2023-07-02T03:30:38+02:00 Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing Ashmore, David W. Hubbard, Bryn Luckman, Adrian Kulessa, Bernd Bevan, Suzanne Booth, Adam Munneke, Peter Kuipers O'Leary, Martin Sevestre, Heidi Holland, Paul R. University of St Andrews. Geography & Sustainable Development 2017-05-31T09:30:14Z 15 application/pdf http://hdl.handle.net/10023/10881 https://doi.org/10.1002/2016JF004047 eng eng Journal of Geophysical Research - Earth Surface Ashmore , D W , Hubbard , B , Luckman , A , Kulessa , B , Bevan , S , Booth , A , Munneke , P K , O'Leary , M , Sevestre , H & Holland , P R 2017 , ' Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing ' , Journal of Geophysical Research - Earth Surface , vol. 122 , no. 5 , pp. 1139-1153 . https://doi.org/10.1002/2016JF004047 2169-9011 PURE: 250139859 PURE UUID: cb91507b-2b5d-47df-98d5-ae2cb0ec5b9d Bibtex: urn:31e4965664a9c419d6dfafab0fa79c6c Scopus: 85019913787 WOS: 000403322100004 http://hdl.handle.net/10023/10881 https://doi.org/10.1002/2016JF004047 © 2017 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. Ice shelves Glaciology Antarctica G Geography (General) DAS G1 Journal article 2017 ftstandrewserep https://doi.org/10.1002/2016JF004047 2023-06-13T18:27:42Z Research was funded by the UK Natural Environmental Research Council grants NE/L006707/1 and NE/L005409/1 and a HEFCW/Aberystwyth University Capital Equipment Grant to B.H. Data will be available via the project website (www.projectmidas.org) and the UK Polar Data Centre (https://www.bas.ac.uk/data/uk-pdc/) from mid-2017. We use borehole optical televiewing (OPTV) to explore the internal structure of Larsen C Ice Shelf (LCIS). We report a suite of five ~90 m long OPTV logs, recording a light-emitting diode-illuminated, geometrically correct image of the borehole wall, from the northern and central sectors of LCIS collected during austral spring 2014 and 2015. We use a thresholding-based technique to estimate the refrozen ice content of the ice column and exploit a recently calibrated density-luminosity relationship to reveal its structure. All sites are dense and strongly influenced by surface melt, with frequent refrozen ice layers and mean densities, between the depths of 1.87 and 90 m, ranging from 862 to 894 kg m−3. We define four distinct units that comprise LCIS and relate these to ice provenance, dynamic history, and past melt events. These units are in situ meteoric ice with infiltration ice (U1), meteoric ice which has undergone enhanced densification (U2), thick refrozen ice (U3), and advected continental ice (U4). We show that the OPTV-derived pattern of firn air content is consistent with previous estimates, but that a significant proportion of firn air is contained within U4, which we interpret to have been deposited inland of the grounding line. The structure of LCIS is strongly influenced by the E-W gradient in föhn-driven melting, with sites close to the Antarctic Peninsula being predominantly composed of refrozen ice. Melting is also substantial toward the ice shelf center with >40% of the overall imaged ice column being composed of refrozen ice. Publisher PDF Peer reviewed Article in Journal/Newspaper Antarc* Antarctic Antarctic Peninsula Antarctica Ice Shelf Ice Shelves University of St Andrews: Digital Research Repository Antarctic Antarctic Peninsula Austral The Antarctic Journal of Geophysical Research: Earth Surface 122 5 1139 1153 |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
Ice shelves Glaciology Antarctica G Geography (General) DAS G1 |
spellingShingle |
Ice shelves Glaciology Antarctica G Geography (General) DAS G1 Ashmore, David W. Hubbard, Bryn Luckman, Adrian Kulessa, Bernd Bevan, Suzanne Booth, Adam Munneke, Peter Kuipers O'Leary, Martin Sevestre, Heidi Holland, Paul R. Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
topic_facet |
Ice shelves Glaciology Antarctica G Geography (General) DAS G1 |
description |
Research was funded by the UK Natural Environmental Research Council grants NE/L006707/1 and NE/L005409/1 and a HEFCW/Aberystwyth University Capital Equipment Grant to B.H. Data will be available via the project website (www.projectmidas.org) and the UK Polar Data Centre (https://www.bas.ac.uk/data/uk-pdc/) from mid-2017. We use borehole optical televiewing (OPTV) to explore the internal structure of Larsen C Ice Shelf (LCIS). We report a suite of five ~90 m long OPTV logs, recording a light-emitting diode-illuminated, geometrically correct image of the borehole wall, from the northern and central sectors of LCIS collected during austral spring 2014 and 2015. We use a thresholding-based technique to estimate the refrozen ice content of the ice column and exploit a recently calibrated density-luminosity relationship to reveal its structure. All sites are dense and strongly influenced by surface melt, with frequent refrozen ice layers and mean densities, between the depths of 1.87 and 90 m, ranging from 862 to 894 kg m−3. We define four distinct units that comprise LCIS and relate these to ice provenance, dynamic history, and past melt events. These units are in situ meteoric ice with infiltration ice (U1), meteoric ice which has undergone enhanced densification (U2), thick refrozen ice (U3), and advected continental ice (U4). We show that the OPTV-derived pattern of firn air content is consistent with previous estimates, but that a significant proportion of firn air is contained within U4, which we interpret to have been deposited inland of the grounding line. The structure of LCIS is strongly influenced by the E-W gradient in föhn-driven melting, with sites close to the Antarctic Peninsula being predominantly composed of refrozen ice. Melting is also substantial toward the ice shelf center with >40% of the overall imaged ice column being composed of refrozen ice. Publisher PDF Peer reviewed |
author2 |
University of St Andrews. Geography & Sustainable Development |
format |
Article in Journal/Newspaper |
author |
Ashmore, David W. Hubbard, Bryn Luckman, Adrian Kulessa, Bernd Bevan, Suzanne Booth, Adam Munneke, Peter Kuipers O'Leary, Martin Sevestre, Heidi Holland, Paul R. |
author_facet |
Ashmore, David W. Hubbard, Bryn Luckman, Adrian Kulessa, Bernd Bevan, Suzanne Booth, Adam Munneke, Peter Kuipers O'Leary, Martin Sevestre, Heidi Holland, Paul R. |
author_sort |
Ashmore, David W. |
title |
Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
title_short |
Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
title_full |
Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
title_fullStr |
Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
title_full_unstemmed |
Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing |
title_sort |
ice and firn heterogeneity within larsen c ice shelf from borehole optical televiewing |
publishDate |
2017 |
url |
http://hdl.handle.net/10023/10881 https://doi.org/10.1002/2016JF004047 |
geographic |
Antarctic Antarctic Peninsula Austral The Antarctic |
geographic_facet |
Antarctic Antarctic Peninsula Austral The Antarctic |
genre |
Antarc* Antarctic Antarctic Peninsula Antarctica Ice Shelf Ice Shelves |
genre_facet |
Antarc* Antarctic Antarctic Peninsula Antarctica Ice Shelf Ice Shelves |
op_relation |
Journal of Geophysical Research - Earth Surface Ashmore , D W , Hubbard , B , Luckman , A , Kulessa , B , Bevan , S , Booth , A , Munneke , P K , O'Leary , M , Sevestre , H & Holland , P R 2017 , ' Ice and firn heterogeneity within Larsen C Ice Shelf from borehole optical televiewing ' , Journal of Geophysical Research - Earth Surface , vol. 122 , no. 5 , pp. 1139-1153 . https://doi.org/10.1002/2016JF004047 2169-9011 PURE: 250139859 PURE UUID: cb91507b-2b5d-47df-98d5-ae2cb0ec5b9d Bibtex: urn:31e4965664a9c419d6dfafab0fa79c6c Scopus: 85019913787 WOS: 000403322100004 http://hdl.handle.net/10023/10881 https://doi.org/10.1002/2016JF004047 |
op_rights |
© 2017 The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. |
op_doi |
https://doi.org/10.1002/2016JF004047 |
container_title |
Journal of Geophysical Research: Earth Surface |
container_volume |
122 |
container_issue |
5 |
container_start_page |
1139 |
op_container_end_page |
1153 |
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1770274841604128768 |