Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology
The use of iceberg-keel ploughmarks as proxy indicators of past and present iceberg morphology, keel depth and drift direction has seldom been approached in the southern hemisphere. Using high-resolution multi-beam swath bathymetry of the mid-shelf Pine Island Trough and outermost Weddell Sea shelf...
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ftdatacite:10.17863/cam.23428 2023-05-15T13:58:58+02:00 Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology Wise, Matthew Geoffrey 2018 https://dx.doi.org/10.17863/cam.23428 https://www.repository.cam.ac.uk/handle/1810/276147 en eng Apollo - University of Cambridge Repository https://www.rioxx.net/licenses/all-rights-reserved/ All Rights Reserved All rights reserved iceberg bathymetry marine geophysics Antarctica Pine Island Bay Weddell Sea Last Glacial Maximum Glaciology Oceanography FOS Earth and related environmental sciences multi-beam swath bathymetry North Falkland Basin Marine Ice-Cliff Instability ploughmarks Text Thesis article-journal ScholarlyArticle 2018 ftdatacite https://doi.org/10.17863/cam.23428 2021-11-05T12:55:41Z The use of iceberg-keel ploughmarks as proxy indicators of past and present iceberg morphology, keel depth and drift direction has seldom been approached in the southern hemisphere. Using high-resolution multi-beam swath bathymetry of the mid-shelf Pine Island Trough and outermost Weddell Sea shelf regions of Antarctica, detailed analysis of >13,000 iceberg-keel ploughmarks was undertaken. By considering the draft of icebergs calved from Antarctica today, calculated from detailed satellite altimetric datasets by this work, almost all observed ploughmarks were interpreted to be relict features. In Pine Island Trough, ploughmark planform parameters and cross-sections imply calving of a large number of non-tabular icebergs with v-shaped keels from the palaeo-Pine Island-Thwaites ice stream. Geological evidence of ploughmark form and modern water depth distribution indicates calving-margin thicknesses (949 m) and subaerial ice cliff elevations (102 m) equivalent to the theoretical threshold predicted to trigger ice-cliff structural collapse and calving by marine ice-cliff instability (MICI) processes. Thus, ploughmarks provide the first observational evidence of rapid retreat of the palaeo-Pine Island-Thwaites ice stream, driven by MICI processes commencing ~12.3 cal ka BP. On the Weddell Sea shelf, ploughmark morphologies imply considerable variation in palaeo-iceberg shape and size, most likely reflecting calving from multiple source margins. In turn, an absence of grounded ice on the Weddell Sea shelf and a palaeo-oceanographic regime comparable to today are implied at the time of formation. Analysis of a 3D seismic cube of the Sea Lion Field area of the North Falkland Basin reveals iceberg-keel ploughmarks incised into the modern- and palaeo-seafloor, formed by icebergs of varying shape and size that most-likely calved from the Antarctic Ice Sheet during three past glacial periods (estimated ages ~18 - 26.5 ka BP, ~246 ka BP, ~9.8 Ma BP). Despite illustrating the possibility of iceberg drift into the North Falkland Basin today, the relict ploughmark age implies little risk to any seafloor structures in the area, which might be required for hydrocarbon production. By these analyses, the significance of iceberg-keel ploughmarks as indicators of palaeo-glaciology and palaeo-oceanography at the time of formation is emphasised. : The work of this Ph.D. thesis was funded by a Natural Environment Research Council (NERC) studentship (LACAF/247 RG72013), awarded by the Department of Geography, University of Cambridge. Thesis Antarc* Antarctic Antarctica Ice Sheet Iceberg* Pine Island Pine Island Bay Weddell Sea DataCite Metadata Store (German National Library of Science and Technology) Antarctic The Antarctic Weddell Sea Weddell Island Bay ENVELOPE(-109.085,-109.085,59.534,59.534) Pine Island Bay ENVELOPE(-102.000,-102.000,-74.750,-74.750) Pine Island Trough ENVELOPE(-101.841,-101.841,-75.011,-75.011) |
institution |
Open Polar |
collection |
DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
topic |
iceberg bathymetry marine geophysics Antarctica Pine Island Bay Weddell Sea Last Glacial Maximum Glaciology Oceanography FOS Earth and related environmental sciences multi-beam swath bathymetry North Falkland Basin Marine Ice-Cliff Instability ploughmarks |
spellingShingle |
iceberg bathymetry marine geophysics Antarctica Pine Island Bay Weddell Sea Last Glacial Maximum Glaciology Oceanography FOS Earth and related environmental sciences multi-beam swath bathymetry North Falkland Basin Marine Ice-Cliff Instability ploughmarks Wise, Matthew Geoffrey Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
topic_facet |
iceberg bathymetry marine geophysics Antarctica Pine Island Bay Weddell Sea Last Glacial Maximum Glaciology Oceanography FOS Earth and related environmental sciences multi-beam swath bathymetry North Falkland Basin Marine Ice-Cliff Instability ploughmarks |
description |
The use of iceberg-keel ploughmarks as proxy indicators of past and present iceberg morphology, keel depth and drift direction has seldom been approached in the southern hemisphere. Using high-resolution multi-beam swath bathymetry of the mid-shelf Pine Island Trough and outermost Weddell Sea shelf regions of Antarctica, detailed analysis of >13,000 iceberg-keel ploughmarks was undertaken. By considering the draft of icebergs calved from Antarctica today, calculated from detailed satellite altimetric datasets by this work, almost all observed ploughmarks were interpreted to be relict features. In Pine Island Trough, ploughmark planform parameters and cross-sections imply calving of a large number of non-tabular icebergs with v-shaped keels from the palaeo-Pine Island-Thwaites ice stream. Geological evidence of ploughmark form and modern water depth distribution indicates calving-margin thicknesses (949 m) and subaerial ice cliff elevations (102 m) equivalent to the theoretical threshold predicted to trigger ice-cliff structural collapse and calving by marine ice-cliff instability (MICI) processes. Thus, ploughmarks provide the first observational evidence of rapid retreat of the palaeo-Pine Island-Thwaites ice stream, driven by MICI processes commencing ~12.3 cal ka BP. On the Weddell Sea shelf, ploughmark morphologies imply considerable variation in palaeo-iceberg shape and size, most likely reflecting calving from multiple source margins. In turn, an absence of grounded ice on the Weddell Sea shelf and a palaeo-oceanographic regime comparable to today are implied at the time of formation. Analysis of a 3D seismic cube of the Sea Lion Field area of the North Falkland Basin reveals iceberg-keel ploughmarks incised into the modern- and palaeo-seafloor, formed by icebergs of varying shape and size that most-likely calved from the Antarctic Ice Sheet during three past glacial periods (estimated ages ~18 - 26.5 ka BP, ~246 ka BP, ~9.8 Ma BP). Despite illustrating the possibility of iceberg drift into the North Falkland Basin today, the relict ploughmark age implies little risk to any seafloor structures in the area, which might be required for hydrocarbon production. By these analyses, the significance of iceberg-keel ploughmarks as indicators of palaeo-glaciology and palaeo-oceanography at the time of formation is emphasised. : The work of this Ph.D. thesis was funded by a Natural Environment Research Council (NERC) studentship (LACAF/247 RG72013), awarded by the Department of Geography, University of Cambridge. |
format |
Thesis |
author |
Wise, Matthew Geoffrey |
author_facet |
Wise, Matthew Geoffrey |
author_sort |
Wise, Matthew Geoffrey |
title |
Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
title_short |
Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
title_full |
Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
title_fullStr |
Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
title_full_unstemmed |
Iceberg-keel ploughmarks on the seafloor of Antarctic continental shelves and the North Falkland Basin: implications for palaeo-glaciology |
title_sort |
iceberg-keel ploughmarks on the seafloor of antarctic continental shelves and the north falkland basin: implications for palaeo-glaciology |
publisher |
Apollo - University of Cambridge Repository |
publishDate |
2018 |
url |
https://dx.doi.org/10.17863/cam.23428 https://www.repository.cam.ac.uk/handle/1810/276147 |
long_lat |
ENVELOPE(-109.085,-109.085,59.534,59.534) ENVELOPE(-102.000,-102.000,-74.750,-74.750) ENVELOPE(-101.841,-101.841,-75.011,-75.011) |
geographic |
Antarctic The Antarctic Weddell Sea Weddell Island Bay Pine Island Bay Pine Island Trough |
geographic_facet |
Antarctic The Antarctic Weddell Sea Weddell Island Bay Pine Island Bay Pine Island Trough |
genre |
Antarc* Antarctic Antarctica Ice Sheet Iceberg* Pine Island Pine Island Bay Weddell Sea |
genre_facet |
Antarc* Antarctic Antarctica Ice Sheet Iceberg* Pine Island Pine Island Bay Weddell Sea |
op_rights |
https://www.rioxx.net/licenses/all-rights-reserved/ All Rights Reserved All rights reserved |
op_doi |
https://doi.org/10.17863/cam.23428 |
_version_ |
1766267339361222656 |