Modelling the development and decay of cryoconite holes in Northwest Greenland
Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablating ice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing the ice sur...
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2023
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ftnonlinearchiv:oai:noa.gwlb.de:cop_mods_00064730 2023-05-15T16:21:27+02:00 Modelling the development and decay of cryoconite holes in Northwest Greenland Onuma, Yukihiko Fujita, Koji Takeuchi, Nozomu Niwano, Masashi Aoki, Teruo 2023-01 electronic https://doi.org/10.5194/egusphere-2023-54 https://noa.gwlb.de/receive/cop_mods_00064730 https://egusphere.copernicus.org/preprints/egusphere-2023-54/egusphere-2023-54.pdf eng eng Copernicus Publications https://doi.org/10.5194/egusphere-2023-54 https://noa.gwlb.de/receive/cop_mods_00064730 https://egusphere.copernicus.org/preprints/egusphere-2023-54/egusphere-2023-54.pdf https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess CC-BY article Verlagsveröffentlichung article Text doc-type:article 2023 ftnonlinearchiv https://doi.org/10.5194/egusphere-2023-54 2023-02-06T00:14:03Z Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablating ice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing the ice surface albedo, accurate simulation of the temporal changes in CH depth is essential for understanding ice surface melt. We established a novel model that simulates the temporal changes in CH depth using heat budgets calculated independently at the ice surface and CH bottom based on hole-shape geometry. We evaluated the model with in situ observations of the CH depths on the Qaanaaq ice cap in Northwest Greenland during the 2012, 2014, and 2017 melt seasons. The model reproduced well the observed depth changes and timing of CH collapse. Although earlier models have shown that CH depth tends to be deeper when downward shortwave radiation is intense, our sensitivity tests suggest that deeper CH tends to form when the diffuse component of downward shortwave radiation is dominant, whereas CHs tend to be shallower when the direct component is dominant. In addition, the total heat flux to the CH bottom is dominated by shortwave radiation transmitted through ice rather than that directly from the CH mouths when the CH is deeper than 10 cm. Furthermore, the tests highlight that the ice surface albedo is a key parameter for accurately reproducing the timing of CH collapse because 0.1 decrease in albedo induces the CH collapse one day earlier. Heat component analysis suggests that CH depth is governed by the balance between the intensity of the diffuse component of downward shortwave radiation and the wind speed. Therefore, these meteorological conditions may be important factors contributing to the recent surface darkening of the Greenland ice sheet and other glaciers via the redistribution of CHs. Coupling the CH model proposed in this study with a climate model should improve our understanding of glacier-surface darkening. Article in Journal/Newspaper glacier Greenland Ice cap Ice Sheet Qaanaaq Niedersächsisches Online-Archiv NOA Greenland Qaanaaq ENVELOPE(-69.232,-69.232,77.467,77.467) |
institution |
Open Polar |
collection |
Niedersächsisches Online-Archiv NOA |
op_collection_id |
ftnonlinearchiv |
language |
English |
topic |
article Verlagsveröffentlichung |
spellingShingle |
article Verlagsveröffentlichung Onuma, Yukihiko Fujita, Koji Takeuchi, Nozomu Niwano, Masashi Aoki, Teruo Modelling the development and decay of cryoconite holes in Northwest Greenland |
topic_facet |
article Verlagsveröffentlichung |
description |
Cryoconite holes (CHs) are water-filled cylindrical holes with cryoconite (dark-coloured sediment) deposited at their bottoms, forming on ablating ice surfaces of glaciers and ice sheets worldwide. Because the collapse of CHs may disperse cryoconite on the ice surface, thereby decreasing the ice surface albedo, accurate simulation of the temporal changes in CH depth is essential for understanding ice surface melt. We established a novel model that simulates the temporal changes in CH depth using heat budgets calculated independently at the ice surface and CH bottom based on hole-shape geometry. We evaluated the model with in situ observations of the CH depths on the Qaanaaq ice cap in Northwest Greenland during the 2012, 2014, and 2017 melt seasons. The model reproduced well the observed depth changes and timing of CH collapse. Although earlier models have shown that CH depth tends to be deeper when downward shortwave radiation is intense, our sensitivity tests suggest that deeper CH tends to form when the diffuse component of downward shortwave radiation is dominant, whereas CHs tend to be shallower when the direct component is dominant. In addition, the total heat flux to the CH bottom is dominated by shortwave radiation transmitted through ice rather than that directly from the CH mouths when the CH is deeper than 10 cm. Furthermore, the tests highlight that the ice surface albedo is a key parameter for accurately reproducing the timing of CH collapse because 0.1 decrease in albedo induces the CH collapse one day earlier. Heat component analysis suggests that CH depth is governed by the balance between the intensity of the diffuse component of downward shortwave radiation and the wind speed. Therefore, these meteorological conditions may be important factors contributing to the recent surface darkening of the Greenland ice sheet and other glaciers via the redistribution of CHs. Coupling the CH model proposed in this study with a climate model should improve our understanding of glacier-surface darkening. |
format |
Article in Journal/Newspaper |
author |
Onuma, Yukihiko Fujita, Koji Takeuchi, Nozomu Niwano, Masashi Aoki, Teruo |
author_facet |
Onuma, Yukihiko Fujita, Koji Takeuchi, Nozomu Niwano, Masashi Aoki, Teruo |
author_sort |
Onuma, Yukihiko |
title |
Modelling the development and decay of cryoconite holes in Northwest Greenland |
title_short |
Modelling the development and decay of cryoconite holes in Northwest Greenland |
title_full |
Modelling the development and decay of cryoconite holes in Northwest Greenland |
title_fullStr |
Modelling the development and decay of cryoconite holes in Northwest Greenland |
title_full_unstemmed |
Modelling the development and decay of cryoconite holes in Northwest Greenland |
title_sort |
modelling the development and decay of cryoconite holes in northwest greenland |
publisher |
Copernicus Publications |
publishDate |
2023 |
url |
https://doi.org/10.5194/egusphere-2023-54 https://noa.gwlb.de/receive/cop_mods_00064730 https://egusphere.copernicus.org/preprints/egusphere-2023-54/egusphere-2023-54.pdf |
long_lat |
ENVELOPE(-69.232,-69.232,77.467,77.467) |
geographic |
Greenland Qaanaaq |
geographic_facet |
Greenland Qaanaaq |
genre |
glacier Greenland Ice cap Ice Sheet Qaanaaq |
genre_facet |
glacier Greenland Ice cap Ice Sheet Qaanaaq |
op_relation |
https://doi.org/10.5194/egusphere-2023-54 https://noa.gwlb.de/receive/cop_mods_00064730 https://egusphere.copernicus.org/preprints/egusphere-2023-54/egusphere-2023-54.pdf |
op_rights |
https://creativecommons.org/licenses/by/4.0/ uneingeschränkt info:eu-repo/semantics/restrictedAccess |
op_rightsnorm |
CC-BY |
op_doi |
https://doi.org/10.5194/egusphere-2023-54 |
_version_ |
1766009460988313600 |