Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland
We present a microstructural characterization of fine-grained layers from the top 90 m of firn from Summit, Greenland, performed using a combination of scanning electron microscopy techniques including secondary electron imaging, energy-dispersive spectroscopy and electron backscattered patterns, an...
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ftdartmouthcoll:oai:digitalcommons.dartmouth.edu:facoa-3942 2023-07-16T03:54:04+02:00 Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland Lomonaco, R. Albert, M. Baker, I. 2011-01-01T08:00:00Z application/pdf https://digitalcommons.dartmouth.edu/facoa/2926 https://doi.org/10.3189/002214311797409730 https://digitalcommons.dartmouth.edu/context/facoa/article/3942/viewcontent/Lomonaco_2011_Microstructural_evolution_of_fine_g.pdf unknown Dartmouth Digital Commons https://digitalcommons.dartmouth.edu/facoa/2926 doi:10.3189/002214311797409730 https://digitalcommons.dartmouth.edu/context/facoa/article/3942/viewcontent/Lomonaco_2011_Microstructural_evolution_of_fine_g.pdf Dartmouth Scholarship polar region impurities electron backscattering tomography ice sheets sampling anisotropy metamorphism dust x-ray imaging dispersive spectrometry secondary electron scanning electron microscopy firn microstructures greenland polar regions arctic region Earth Sciences Glaciology Physical Sciences and Mathematics text 2011 ftdartmouthcoll https://doi.org/10.3189/002214311797409730 2023-06-28T10:44:07Z We present a microstructural characterization of fine-grained layers from the top 90 m of firn from Summit, Greenland, performed using a combination of scanning electron microscopy techniques including secondary electron imaging, energy-dispersive spectroscopy and electron backscattered patterns, and X-ray microcomputed tomography. The impurities in the firn, both soluble impurities and dust particles, were found largely in the grain interiors. Both c- and a-axis pole figures do not show strong evidence of a preferred orientation of the grains even at the bottom of the firn column. The firn structure became increasingly anisotropic with vertical alignment in the top 3 m, probably due to vapor transport associated with dry-snow metamorphism. The anisotropy decreases below this level until at ∼50 m the average firn structure is close to isotropic. In the near surface, the level of anisotropy is weaker than at Hercules Dome, Antarctica, confirming that differences in accumulation rates and temperatures leave enduring evidence in the structure of the firn. The fraction of closed-off pores is relatively low until ∼65 m; below that it rises through the end of our sampling at 90 m. Our microstructure measurements on the microscale are consistent with in situ firn-air sampling measurements on a decimeter scale, both indicating the existence of the lock-in zone starting near 69 m depth, and pore close-off at 81 m at this site. Text Antarc* Antarctica Arctic Greenland Dartmouth Digital Commons (Dartmouth College) Arctic Greenland Hercules ENVELOPE(161.450,161.450,-77.483,-77.483) Hercules Dome ENVELOPE(-105.000,-105.000,-86.000,-86.000) Journal of Glaciology 57 204 755 762 |
institution |
Open Polar |
collection |
Dartmouth Digital Commons (Dartmouth College) |
op_collection_id |
ftdartmouthcoll |
language |
unknown |
topic |
polar region impurities electron backscattering tomography ice sheets sampling anisotropy metamorphism dust x-ray imaging dispersive spectrometry secondary electron scanning electron microscopy firn microstructures greenland polar regions arctic region Earth Sciences Glaciology Physical Sciences and Mathematics |
spellingShingle |
polar region impurities electron backscattering tomography ice sheets sampling anisotropy metamorphism dust x-ray imaging dispersive spectrometry secondary electron scanning electron microscopy firn microstructures greenland polar regions arctic region Earth Sciences Glaciology Physical Sciences and Mathematics Lomonaco, R. Albert, M. Baker, I. Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
topic_facet |
polar region impurities electron backscattering tomography ice sheets sampling anisotropy metamorphism dust x-ray imaging dispersive spectrometry secondary electron scanning electron microscopy firn microstructures greenland polar regions arctic region Earth Sciences Glaciology Physical Sciences and Mathematics |
description |
We present a microstructural characterization of fine-grained layers from the top 90 m of firn from Summit, Greenland, performed using a combination of scanning electron microscopy techniques including secondary electron imaging, energy-dispersive spectroscopy and electron backscattered patterns, and X-ray microcomputed tomography. The impurities in the firn, both soluble impurities and dust particles, were found largely in the grain interiors. Both c- and a-axis pole figures do not show strong evidence of a preferred orientation of the grains even at the bottom of the firn column. The firn structure became increasingly anisotropic with vertical alignment in the top 3 m, probably due to vapor transport associated with dry-snow metamorphism. The anisotropy decreases below this level until at ∼50 m the average firn structure is close to isotropic. In the near surface, the level of anisotropy is weaker than at Hercules Dome, Antarctica, confirming that differences in accumulation rates and temperatures leave enduring evidence in the structure of the firn. The fraction of closed-off pores is relatively low until ∼65 m; below that it rises through the end of our sampling at 90 m. Our microstructure measurements on the microscale are consistent with in situ firn-air sampling measurements on a decimeter scale, both indicating the existence of the lock-in zone starting near 69 m depth, and pore close-off at 81 m at this site. |
format |
Text |
author |
Lomonaco, R. Albert, M. Baker, I. |
author_facet |
Lomonaco, R. Albert, M. Baker, I. |
author_sort |
Lomonaco, R. |
title |
Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
title_short |
Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
title_full |
Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
title_fullStr |
Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
title_full_unstemmed |
Microstructural Evolution of Fine-Grained Layers through the Firn Column at Summit, Greenland |
title_sort |
microstructural evolution of fine-grained layers through the firn column at summit, greenland |
publisher |
Dartmouth Digital Commons |
publishDate |
2011 |
url |
https://digitalcommons.dartmouth.edu/facoa/2926 https://doi.org/10.3189/002214311797409730 https://digitalcommons.dartmouth.edu/context/facoa/article/3942/viewcontent/Lomonaco_2011_Microstructural_evolution_of_fine_g.pdf |
long_lat |
ENVELOPE(161.450,161.450,-77.483,-77.483) ENVELOPE(-105.000,-105.000,-86.000,-86.000) |
geographic |
Arctic Greenland Hercules Hercules Dome |
geographic_facet |
Arctic Greenland Hercules Hercules Dome |
genre |
Antarc* Antarctica Arctic Greenland |
genre_facet |
Antarc* Antarctica Arctic Greenland |
op_source |
Dartmouth Scholarship |
op_relation |
https://digitalcommons.dartmouth.edu/facoa/2926 doi:10.3189/002214311797409730 https://digitalcommons.dartmouth.edu/context/facoa/article/3942/viewcontent/Lomonaco_2011_Microstructural_evolution_of_fine_g.pdf |
op_doi |
https://doi.org/10.3189/002214311797409730 |
container_title |
Journal of Glaciology |
container_volume |
57 |
container_issue |
204 |
container_start_page |
755 |
op_container_end_page |
762 |
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1771551282295734272 |