Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks.
Marine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 metres below sea level are lost. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to ret...
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ftunivcam:oai:www.repository.cam.ac.uk:1810/275729 2024-02-04T09:55:25+01:00 Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. Wise, Matthew G Dowdeswell, Julian A Jakobsson, Martin Larter, Robert D 2017-10-25 Print application/pdf https://www.repository.cam.ac.uk/handle/1810/275729 https://doi.org/10.17863/CAM.22993 eng eng Springer Science and Business Media LLC http://dx.doi.org/10.1038/nature24458 Nature https://www.repository.cam.ac.uk/handle/1810/275729 doi:10.17863/CAM.22993 0406 Physical Geography and Environmental Geoscience 0403 Geology Article 2017 ftunivcam https://doi.org/10.17863/CAM.22993 2024-01-11T23:19:49Z Marine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 metres below sea level are lost. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to retreat only short distances before they reach extensive retrograde slopes. When grounding zones of glaciers retreat onto such slopes, theoretical considerations and modelling results indicate that the retreat becomes unstable (marine ice-sheet instability) and thus accelerates. It is thought that MICI is triggered when this retreat produces ice cliffs above the water line with heights approaching about 90 metres. However, observational evidence confirming the action of MICI has not previously been reported. Here we present observational evidence that rapid deglacial ice-sheet retreat into Pine Island Bay proceeded in a similar manner to that simulated in a recent modelling study, driven by MICI. Iceberg-keel plough marks on the sea-floor provide geological evidence of past and present iceberg morphology, keel depth and drift direction. From the planform shape and cross-sectional morphologies of iceberg-keel plough marks, we find that iceberg calving during the most recent deglaciation was not characterized by small numbers of large, tabular icebergs as is observed today, which would produce wide, flat-based plough marks or toothcomb-like multi-keeled plough marks. Instead, it was characterized by large numbers of smaller icebergs with V-shaped keels. Geological evidence of the form and water-depth distribution of the plough marks indicates calving-margin thicknesses equivalent to the threshold that is predicted to trigger ice-cliff structural collapse as a result of MICI. We infer rapid and sustained ice-sheet retreat driven by MICI, commencing around 12,300 years ago and terminating before about 11,200 years ago, which produced large numbers of icebergs smaller than the typical tabular icebergs produced today. Our ... Article in Journal/Newspaper Antarc* Antarctic Antarctica Ice Sheet Ice Shelves Iceberg* Pine Island Pine Island Bay West Antarctica Apollo - University of Cambridge Repository Antarctic The Antarctic West Antarctica Island Bay ENVELOPE(-109.085,-109.085,59.534,59.534) Pine Island Bay ENVELOPE(-102.000,-102.000,-74.750,-74.750) Buttress ENVELOPE(-57.083,-57.083,-63.550,-63.550) |
institution |
Open Polar |
collection |
Apollo - University of Cambridge Repository |
op_collection_id |
ftunivcam |
language |
English |
topic |
0406 Physical Geography and Environmental Geoscience 0403 Geology |
spellingShingle |
0406 Physical Geography and Environmental Geoscience 0403 Geology Wise, Matthew G Dowdeswell, Julian A Jakobsson, Martin Larter, Robert D Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
topic_facet |
0406 Physical Geography and Environmental Geoscience 0403 Geology |
description |
Marine ice-cliff instability (MICI) processes could accelerate future retreat of the Antarctic Ice Sheet if ice shelves that buttress grounding lines more than 800 metres below sea level are lost. The present-day grounding zones of the Pine Island and Thwaites glaciers in West Antarctica need to retreat only short distances before they reach extensive retrograde slopes. When grounding zones of glaciers retreat onto such slopes, theoretical considerations and modelling results indicate that the retreat becomes unstable (marine ice-sheet instability) and thus accelerates. It is thought that MICI is triggered when this retreat produces ice cliffs above the water line with heights approaching about 90 metres. However, observational evidence confirming the action of MICI has not previously been reported. Here we present observational evidence that rapid deglacial ice-sheet retreat into Pine Island Bay proceeded in a similar manner to that simulated in a recent modelling study, driven by MICI. Iceberg-keel plough marks on the sea-floor provide geological evidence of past and present iceberg morphology, keel depth and drift direction. From the planform shape and cross-sectional morphologies of iceberg-keel plough marks, we find that iceberg calving during the most recent deglaciation was not characterized by small numbers of large, tabular icebergs as is observed today, which would produce wide, flat-based plough marks or toothcomb-like multi-keeled plough marks. Instead, it was characterized by large numbers of smaller icebergs with V-shaped keels. Geological evidence of the form and water-depth distribution of the plough marks indicates calving-margin thicknesses equivalent to the threshold that is predicted to trigger ice-cliff structural collapse as a result of MICI. We infer rapid and sustained ice-sheet retreat driven by MICI, commencing around 12,300 years ago and terminating before about 11,200 years ago, which produced large numbers of icebergs smaller than the typical tabular icebergs produced today. Our ... |
format |
Article in Journal/Newspaper |
author |
Wise, Matthew G Dowdeswell, Julian A Jakobsson, Martin Larter, Robert D |
author_facet |
Wise, Matthew G Dowdeswell, Julian A Jakobsson, Martin Larter, Robert D |
author_sort |
Wise, Matthew G |
title |
Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
title_short |
Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
title_full |
Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
title_fullStr |
Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
title_full_unstemmed |
Evidence of marine ice-cliff instability in Pine Island Bay from iceberg-keel plough marks. |
title_sort |
evidence of marine ice-cliff instability in pine island bay from iceberg-keel plough marks. |
publisher |
Springer Science and Business Media LLC |
publishDate |
2017 |
url |
https://www.repository.cam.ac.uk/handle/1810/275729 https://doi.org/10.17863/CAM.22993 |
long_lat |
ENVELOPE(-109.085,-109.085,59.534,59.534) ENVELOPE(-102.000,-102.000,-74.750,-74.750) ENVELOPE(-57.083,-57.083,-63.550,-63.550) |
geographic |
Antarctic The Antarctic West Antarctica Island Bay Pine Island Bay Buttress |
geographic_facet |
Antarctic The Antarctic West Antarctica Island Bay Pine Island Bay Buttress |
genre |
Antarc* Antarctic Antarctica Ice Sheet Ice Shelves Iceberg* Pine Island Pine Island Bay West Antarctica |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet Ice Shelves Iceberg* Pine Island Pine Island Bay West Antarctica |
op_relation |
https://www.repository.cam.ac.uk/handle/1810/275729 doi:10.17863/CAM.22993 |
op_doi |
https://doi.org/10.17863/CAM.22993 |
_version_ |
1789959393667710976 |