Grain-size evolution controls the accumulation dependence of modelled firn thickness
The net rate of snow accumulation b is predicted to increase over large areas of the Antarctic and Greenland ice sheets as the climate warms. Models disagree on how this will affect the thickness of the firn layer – the relatively low-density upper layer of the ice sheets that influences altimetric...
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Copernicus Publications
2022
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Online Access: | https://doi.org/10.5194/tc-16-3413-2022 https://tc.copernicus.org/articles/16/3413/2022/tc-16-3413-2022.pdf https://doaj.org/article/40d2bac38f53479eb8c0d5e87161ece1 |
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fttriple:oai:gotriple.eu:oai:doaj.org/article:40d2bac38f53479eb8c0d5e87161ece1 2023-05-15T13:48:38+02:00 Grain-size evolution controls the accumulation dependence of modelled firn thickness J. Kingslake R. Skarbek E. Case C. McCarthy 2022-08-01 https://doi.org/10.5194/tc-16-3413-2022 https://tc.copernicus.org/articles/16/3413/2022/tc-16-3413-2022.pdf https://doaj.org/article/40d2bac38f53479eb8c0d5e87161ece1 en eng Copernicus Publications doi:10.5194/tc-16-3413-2022 1994-0416 1994-0424 https://tc.copernicus.org/articles/16/3413/2022/tc-16-3413-2022.pdf https://doaj.org/article/40d2bac38f53479eb8c0d5e87161ece1 undefined The Cryosphere, Vol 16, Pp 3413-3430 (2022) geo envir Journal Article https://vocabularies.coar-repositories.org/resource_types/c_6501/ 2022 fttriple https://doi.org/10.5194/tc-16-3413-2022 2023-01-22T19:34:09Z The net rate of snow accumulation b is predicted to increase over large areas of the Antarctic and Greenland ice sheets as the climate warms. Models disagree on how this will affect the thickness of the firn layer – the relatively low-density upper layer of the ice sheets that influences altimetric observations of ice sheet mass change and palaeo-climate reconstructions from ice cores. Here we examine how b influences firn compaction and porosity in a simplified model that accounts for mass conservation, dry firn compaction, grain-size evolution, and the impact of grain size on firn compaction. Treating b as a boundary condition and employing an Eulerian reference frame helps to untangle the factors controlling the b dependence of firn thickness. We present numerical simulations using the model, as well as simplified steady-state approximations to the full model, to demonstrate how the downward advection of porosity and grain size are both affected by b but have opposing impacts on firn thickness. The net result is that firn thickness increases with b and that the strength of this dependence increases with increasing surface grain size. We also quantify the circumstances under which porosity advection and grain-size advection balance exactly, which counterintuitively renders steady-state firn thickness independent of b. These findings are qualitatively independent of the stress-dependence of firn compaction and whether the thickness of the ice sheet is increasing, decreasing, or steady. They do depend on the grain-size dependence of firn compaction. Firn models usually ignore grain-size evolution, but we highlight the complex effect it can have on firn thickness when included in a simplified model. This work motivates future efforts to better observationally constrain the rheological effect of grain size in firn. Article in Journal/Newspaper Antarc* Antarctic Greenland Ice Sheet The Cryosphere Unknown Antarctic Greenland The Antarctic The Cryosphere 16 9 3413 3430 |
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geo envir J. Kingslake R. Skarbek E. Case C. McCarthy Grain-size evolution controls the accumulation dependence of modelled firn thickness |
topic_facet |
geo envir |
description |
The net rate of snow accumulation b is predicted to increase over large areas of the Antarctic and Greenland ice sheets as the climate warms. Models disagree on how this will affect the thickness of the firn layer – the relatively low-density upper layer of the ice sheets that influences altimetric observations of ice sheet mass change and palaeo-climate reconstructions from ice cores. Here we examine how b influences firn compaction and porosity in a simplified model that accounts for mass conservation, dry firn compaction, grain-size evolution, and the impact of grain size on firn compaction. Treating b as a boundary condition and employing an Eulerian reference frame helps to untangle the factors controlling the b dependence of firn thickness. We present numerical simulations using the model, as well as simplified steady-state approximations to the full model, to demonstrate how the downward advection of porosity and grain size are both affected by b but have opposing impacts on firn thickness. The net result is that firn thickness increases with b and that the strength of this dependence increases with increasing surface grain size. We also quantify the circumstances under which porosity advection and grain-size advection balance exactly, which counterintuitively renders steady-state firn thickness independent of b. These findings are qualitatively independent of the stress-dependence of firn compaction and whether the thickness of the ice sheet is increasing, decreasing, or steady. They do depend on the grain-size dependence of firn compaction. Firn models usually ignore grain-size evolution, but we highlight the complex effect it can have on firn thickness when included in a simplified model. This work motivates future efforts to better observationally constrain the rheological effect of grain size in firn. |
format |
Article in Journal/Newspaper |
author |
J. Kingslake R. Skarbek E. Case C. McCarthy |
author_facet |
J. Kingslake R. Skarbek E. Case C. McCarthy |
author_sort |
J. Kingslake |
title |
Grain-size evolution controls the accumulation dependence of modelled firn thickness |
title_short |
Grain-size evolution controls the accumulation dependence of modelled firn thickness |
title_full |
Grain-size evolution controls the accumulation dependence of modelled firn thickness |
title_fullStr |
Grain-size evolution controls the accumulation dependence of modelled firn thickness |
title_full_unstemmed |
Grain-size evolution controls the accumulation dependence of modelled firn thickness |
title_sort |
grain-size evolution controls the accumulation dependence of modelled firn thickness |
publisher |
Copernicus Publications |
publishDate |
2022 |
url |
https://doi.org/10.5194/tc-16-3413-2022 https://tc.copernicus.org/articles/16/3413/2022/tc-16-3413-2022.pdf https://doaj.org/article/40d2bac38f53479eb8c0d5e87161ece1 |
geographic |
Antarctic Greenland The Antarctic |
geographic_facet |
Antarctic Greenland The Antarctic |
genre |
Antarc* Antarctic Greenland Ice Sheet The Cryosphere |
genre_facet |
Antarc* Antarctic Greenland Ice Sheet The Cryosphere |
op_source |
The Cryosphere, Vol 16, Pp 3413-3430 (2022) |
op_relation |
doi:10.5194/tc-16-3413-2022 1994-0416 1994-0424 https://tc.copernicus.org/articles/16/3413/2022/tc-16-3413-2022.pdf https://doaj.org/article/40d2bac38f53479eb8c0d5e87161ece1 |
op_rights |
undefined |
op_doi |
https://doi.org/10.5194/tc-16-3413-2022 |
container_title |
The Cryosphere |
container_volume |
16 |
container_issue |
9 |
container_start_page |
3413 |
op_container_end_page |
3430 |
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1766249524846657536 |