Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum
We present the first age control and sedimentological data for the upper part of a stratified seismic unit that is unusually thick (~6-9 m) for the outer shelf of the ASE and overlies an acoustically transparent unit. The transparent unit probably consists of soft till deposited during the last adva...
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ftawi:oai:epic.awi.de:41680 2023-05-15T13:24:19+02:00 Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum Klages, Johann Philipp Kuhn, Gerhard Hillenbrand, Claus-Dieter Smith, James A. Graham, Alastair G. C. Gohl, Karsten Wacker, Lukas 2016 https://epic.awi.de/id/eprint/41680/ https://agu.confex.com/agu/os16/meetingapp.cgi/Paper/87009 https://hdl.handle.net/10013/epic.48540 unknown Klages, J. P. orcid:0000-0003-0968-1183 , Kuhn, G. orcid:0000-0001-6069-7485 , Hillenbrand, C. D. , Smith, J. A. , Graham, A. G. C. , Gohl, K. orcid:0000-0002-9558-2116 and Wacker, L. (2016) Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum , AGU Ocean Sciences Meeting, New Orleans, Louisiana, USA, 21 February 2016 - 26 February 2016 . hdl:10013/epic.48540 EPIC3AGU Ocean Sciences Meeting, New Orleans, Louisiana, USA, 2016-02-21-2016-02-26 Conference notRev 2016 ftawi 2021-12-24T15:41:51Z We present the first age control and sedimentological data for the upper part of a stratified seismic unit that is unusually thick (~6-9 m) for the outer shelf of the ASE and overlies an acoustically transparent unit. The transparent unit probably consists of soft till deposited during the last advance of grounded ice onto the outer shelf. We mapped subtle mega-scale glacial lineations (MSGL) on the seafloor and suggest that these are probably the expressions of bedforms originally moulded into the surface of the underlying till layer. We note that the lineations are less distinct when compared to MSGLs recorded in bathymetric data collected further upstream and suggest that this is because of the blanketing influence of the thick overlying drape. The uppermost part (≤ 3 m) of the stratified drape was sampled by two of our sediment cores and contains sufficient amounts of calcareous foraminifera throughout to establish reliable age models by radiocarbon dating. In combination with facies analysis of the recovered sediments the obtained radiocarbon dates suggest deposition of the draping unit in a sub-ice shelf/sub-sea ice to seasonal-open marine environment that existed on the outer shelf from well before (>45 ka BP) the Last Glacial Maximum until today. This indicates the maximum extent of grounded ice at the LGM must have been situated south of the two core locations, where a well-defined grounding-zone wedge (‘GZWa’) was deposited. The third sediment core was recovered from the toe of this wedge and retrieved grounding-line proximal glaciogenic debris flow sediments that were deposited by ~14 cal. ka BP. Our new data therefore provide direct evidence for 1) the maximum extent of grounded ice in the easternmost ASE at the LGM (=GZWa), 2) the existence of a large shelf area seawards the wedge that was not covered by grounded ice during that time, and 3) landward grounding line retreat from GZWa prior to ~14 cal. ka BP. This knowledge will help to improve LGM ice sheet reconstructions and to quantify precisely the volume of LGM ice-sheet build-up in Antarctica. Our study also alludes to the possibility that refugia for Antarctic shelf benthos may have existed in the ASE during the last glacial period. Conference Object Amundsen Sea Antarc* Antarctic Antarctica Ice Sheet Ice Shelf Sea ice Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) Antarctic Amundsen Sea West Antarctic Ice Sheet The Toe ENVELOPE(-59.167,-59.167,-62.333,-62.333) |
institution |
Open Polar |
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Alfred Wegener Institute for Polar- and Marine Research (AWI): ePIC (electronic Publication Information Center) |
op_collection_id |
ftawi |
language |
unknown |
description |
We present the first age control and sedimentological data for the upper part of a stratified seismic unit that is unusually thick (~6-9 m) for the outer shelf of the ASE and overlies an acoustically transparent unit. The transparent unit probably consists of soft till deposited during the last advance of grounded ice onto the outer shelf. We mapped subtle mega-scale glacial lineations (MSGL) on the seafloor and suggest that these are probably the expressions of bedforms originally moulded into the surface of the underlying till layer. We note that the lineations are less distinct when compared to MSGLs recorded in bathymetric data collected further upstream and suggest that this is because of the blanketing influence of the thick overlying drape. The uppermost part (≤ 3 m) of the stratified drape was sampled by two of our sediment cores and contains sufficient amounts of calcareous foraminifera throughout to establish reliable age models by radiocarbon dating. In combination with facies analysis of the recovered sediments the obtained radiocarbon dates suggest deposition of the draping unit in a sub-ice shelf/sub-sea ice to seasonal-open marine environment that existed on the outer shelf from well before (>45 ka BP) the Last Glacial Maximum until today. This indicates the maximum extent of grounded ice at the LGM must have been situated south of the two core locations, where a well-defined grounding-zone wedge (‘GZWa’) was deposited. The third sediment core was recovered from the toe of this wedge and retrieved grounding-line proximal glaciogenic debris flow sediments that were deposited by ~14 cal. ka BP. Our new data therefore provide direct evidence for 1) the maximum extent of grounded ice in the easternmost ASE at the LGM (=GZWa), 2) the existence of a large shelf area seawards the wedge that was not covered by grounded ice during that time, and 3) landward grounding line retreat from GZWa prior to ~14 cal. ka BP. This knowledge will help to improve LGM ice sheet reconstructions and to quantify precisely the volume of LGM ice-sheet build-up in Antarctica. Our study also alludes to the possibility that refugia for Antarctic shelf benthos may have existed in the ASE during the last glacial period. |
format |
Conference Object |
author |
Klages, Johann Philipp Kuhn, Gerhard Hillenbrand, Claus-Dieter Smith, James A. Graham, Alastair G. C. Gohl, Karsten Wacker, Lukas |
spellingShingle |
Klages, Johann Philipp Kuhn, Gerhard Hillenbrand, Claus-Dieter Smith, James A. Graham, Alastair G. C. Gohl, Karsten Wacker, Lukas Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
author_facet |
Klages, Johann Philipp Kuhn, Gerhard Hillenbrand, Claus-Dieter Smith, James A. Graham, Alastair G. C. Gohl, Karsten Wacker, Lukas |
author_sort |
Klages, Johann Philipp |
title |
Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
title_short |
Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
title_full |
Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
title_fullStr |
Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
title_full_unstemmed |
Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum |
title_sort |
reliable radiocarbon evidence for the maximum extent of the west antarctic ice sheet in the easternmost amundsen sea embayment during the last glacial maximum |
publishDate |
2016 |
url |
https://epic.awi.de/id/eprint/41680/ https://agu.confex.com/agu/os16/meetingapp.cgi/Paper/87009 https://hdl.handle.net/10013/epic.48540 |
long_lat |
ENVELOPE(-59.167,-59.167,-62.333,-62.333) |
geographic |
Antarctic Amundsen Sea West Antarctic Ice Sheet The Toe |
geographic_facet |
Antarctic Amundsen Sea West Antarctic Ice Sheet The Toe |
genre |
Amundsen Sea Antarc* Antarctic Antarctica Ice Sheet Ice Shelf Sea ice |
genre_facet |
Amundsen Sea Antarc* Antarctic Antarctica Ice Sheet Ice Shelf Sea ice |
op_source |
EPIC3AGU Ocean Sciences Meeting, New Orleans, Louisiana, USA, 2016-02-21-2016-02-26 |
op_relation |
Klages, J. P. orcid:0000-0003-0968-1183 , Kuhn, G. orcid:0000-0001-6069-7485 , Hillenbrand, C. D. , Smith, J. A. , Graham, A. G. C. , Gohl, K. orcid:0000-0002-9558-2116 and Wacker, L. (2016) Reliable radiocarbon evidence for the maximum extent of the West Antarctic Ice Sheet in the easternmost Amundsen Sea Embayment during the Last Glacial Maximum , AGU Ocean Sciences Meeting, New Orleans, Louisiana, USA, 21 February 2016 - 26 February 2016 . hdl:10013/epic.48540 |
_version_ |
1766378718711775232 |