Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice
Microstructures from deep ice cores reflect the dynamic conditions of the drill location as well as the thermodynamic history of the drill site and catchment area in great detail. Ice core parameters (crystal lattice-preferred orientation (LPO), grain size, grain shape), mesostructures (visual strat...
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ftdatacite:10.23689/fidgeo-2536 2023-05-15T13:30:25+02:00 Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice Weikusat, Ilka Jansen, Daniela Binder, Tobias Eichler, Jan Faria, Sérgio H. Wilhelms, Frank Kipfstuhl, Sepp Sheldon, Simon Miller, Heinrich Dahl-Jensen, Dorthe Kleiner, Thomas 2016 https://dx.doi.org/10.23689/fidgeo-2536 https://e-docs.geo-leo.de/handle/11858/6849 en eng FID GEO Text Article article-journal ScholarlyArticle 2016 ftdatacite https://doi.org/10.23689/fidgeo-2536 2021-11-05T12:55:41Z Microstructures from deep ice cores reflect the dynamic conditions of the drill location as well as the thermodynamic history of the drill site and catchment area in great detail. Ice core parameters (crystal lattice-preferred orientation (LPO), grain size, grain shape), mesostructures (visual stratigraphy) as well as borehole deformation were measured in a deep ice core drilled at Kohnen Station, Dronning Maud Land (DML), Antarctica. These observations are used to characterize the local dynamic setting and its rheological as well as microstructural effects at the EDML ice core drilling site (European Project for Ice Coring in Antarctica in DML). The results suggest a division of the core into five distinct sections, interpreted as the effects of changing deformation boundary conditions from triaxial deformation with horizontal extension to bedrock-parallel shear. Region 1 (uppermost approx. 450 m depth) with still small macroscopic strain is dominated by compression of bubbles and strong strain and recrystallization localization. Region 2 (approx. 450–1700 m depth) shows a girdle-type LPO with the girdle plane being perpendicular to grain elongations, which indicates triaxial deformation with dominating horizontal extension. In this region (approx. 1000 m depth), the first subtle traces of shear deformation are observed in the shape-preferred orientation (SPO) by inclination of the grain elongation. Region 3 (approx. 1700–2030 m depth) represents a transitional regime between triaxial deformation and dominance of shear, which becomes apparent in the progression of the girdle to a single maximum LPO and increasing obliqueness of grain elongations. The fully developed single maximum LPO in region 4 (approx. 2030–2385 m depth) is an indicator of shear dominance. Region 5 (below approx. 2385 m depth) is marked by signs of strong shear, such as strong SPO values of grain elongation and strong kink folding of visual layers. The details of structural observations are compared with results from a numerical ice sheet model (PISM, isotropic) for comparison of strain rate trends predicted from the large-scale geometry of the ice sheet and borehole logging data. This comparison confirms the segmentation into these depth regions and in turn provides a wider view of the ice sheet. Text Antarc* Antarctic Antarctica DML Dronning Maud Land ice core Ice Sheet DataCite Metadata Store (German National Library of Science and Technology) Antarctic Dronning Maud Land Kohnen ENVELOPE(0.000,0.000,-75.000,-75.000) Kohnen Station ENVELOPE(0.000,0.000,-75.000,-75.000) |
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Open Polar |
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DataCite Metadata Store (German National Library of Science and Technology) |
op_collection_id |
ftdatacite |
language |
English |
description |
Microstructures from deep ice cores reflect the dynamic conditions of the drill location as well as the thermodynamic history of the drill site and catchment area in great detail. Ice core parameters (crystal lattice-preferred orientation (LPO), grain size, grain shape), mesostructures (visual stratigraphy) as well as borehole deformation were measured in a deep ice core drilled at Kohnen Station, Dronning Maud Land (DML), Antarctica. These observations are used to characterize the local dynamic setting and its rheological as well as microstructural effects at the EDML ice core drilling site (European Project for Ice Coring in Antarctica in DML). The results suggest a division of the core into five distinct sections, interpreted as the effects of changing deformation boundary conditions from triaxial deformation with horizontal extension to bedrock-parallel shear. Region 1 (uppermost approx. 450 m depth) with still small macroscopic strain is dominated by compression of bubbles and strong strain and recrystallization localization. Region 2 (approx. 450–1700 m depth) shows a girdle-type LPO with the girdle plane being perpendicular to grain elongations, which indicates triaxial deformation with dominating horizontal extension. In this region (approx. 1000 m depth), the first subtle traces of shear deformation are observed in the shape-preferred orientation (SPO) by inclination of the grain elongation. Region 3 (approx. 1700–2030 m depth) represents a transitional regime between triaxial deformation and dominance of shear, which becomes apparent in the progression of the girdle to a single maximum LPO and increasing obliqueness of grain elongations. The fully developed single maximum LPO in region 4 (approx. 2030–2385 m depth) is an indicator of shear dominance. Region 5 (below approx. 2385 m depth) is marked by signs of strong shear, such as strong SPO values of grain elongation and strong kink folding of visual layers. The details of structural observations are compared with results from a numerical ice sheet model (PISM, isotropic) for comparison of strain rate trends predicted from the large-scale geometry of the ice sheet and borehole logging data. This comparison confirms the segmentation into these depth regions and in turn provides a wider view of the ice sheet. |
format |
Text |
author |
Weikusat, Ilka Jansen, Daniela Binder, Tobias Eichler, Jan Faria, Sérgio H. Wilhelms, Frank Kipfstuhl, Sepp Sheldon, Simon Miller, Heinrich Dahl-Jensen, Dorthe Kleiner, Thomas |
spellingShingle |
Weikusat, Ilka Jansen, Daniela Binder, Tobias Eichler, Jan Faria, Sérgio H. Wilhelms, Frank Kipfstuhl, Sepp Sheldon, Simon Miller, Heinrich Dahl-Jensen, Dorthe Kleiner, Thomas Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
author_facet |
Weikusat, Ilka Jansen, Daniela Binder, Tobias Eichler, Jan Faria, Sérgio H. Wilhelms, Frank Kipfstuhl, Sepp Sheldon, Simon Miller, Heinrich Dahl-Jensen, Dorthe Kleiner, Thomas |
author_sort |
Weikusat, Ilka |
title |
Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
title_short |
Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
title_full |
Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
title_fullStr |
Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
title_full_unstemmed |
Physical analysis of an Antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
title_sort |
physical analysis of an antarctic ice core—towards an integration of micro- and macrodynamics of polar ice |
publisher |
FID GEO |
publishDate |
2016 |
url |
https://dx.doi.org/10.23689/fidgeo-2536 https://e-docs.geo-leo.de/handle/11858/6849 |
long_lat |
ENVELOPE(0.000,0.000,-75.000,-75.000) ENVELOPE(0.000,0.000,-75.000,-75.000) |
geographic |
Antarctic Dronning Maud Land Kohnen Kohnen Station |
geographic_facet |
Antarctic Dronning Maud Land Kohnen Kohnen Station |
genre |
Antarc* Antarctic Antarctica DML Dronning Maud Land ice core Ice Sheet |
genre_facet |
Antarc* Antarctic Antarctica DML Dronning Maud Land ice core Ice Sheet |
op_doi |
https://doi.org/10.23689/fidgeo-2536 |
_version_ |
1766007970923020288 |