An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020)
The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface...
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ftcopernicus:oai:publications.copernicus.org:tc107769 2023-06-18T03:40:55+02:00 An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) Thompson-Munson, Megan Wever, Nander Stevens, C. Max Lenaerts, Jan T. M. Medley, Brooke 2023-05-30 application/pdf https://doi.org/10.5194/tc-17-2185-2023 https://tc.copernicus.org/articles/17/2185/2023/ eng eng doi:10.5194/tc-17-2185-2023 https://tc.copernicus.org/articles/17/2185/2023/ eISSN: 1994-0424 Text 2023 ftcopernicus https://doi.org/10.5194/tc-17-2185-2023 2023-06-05T16:24:05Z The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface ice slabs in the firn. Understanding how firn properties respond to climate is important for constraining the GrIS's future contribution to sea level rise in a warming climate. Observations of firn density provide detailed information about firn properties, but they are spatially and temporally limited. Here we use two firn models, the physics-based SNOWPACK model and the Community Firn Model configured with a semi-empirical densification equation (CFM-GSFC), to quantify firn properties across the GrIS from 1980 through 2020. We use an identical forcing (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) atmospheric reanalysis) for SNOWPACK and the CFM-GSFC in order to isolate firn model differences. To evaluate the models, we compare simulated firn properties, including firn air content (FAC), to measurements from the Surface Mass Balance and Snow on Sea Ice Working Group (SUMup) dataset of snow and firn density. Both models perform well (mean absolute percentage errors of 14 % in SNOWPACK and 16 % in the CFM-GSFC), though their performance is hindered by the spatial resolution of the atmospheric forcing. In the ice-sheet-wide simulations, the 1980–1995 average spatially integrated FAC (i.e., air volume in the firn) for the upper 100 m is 34 645 km 3 from SNOWPACK and 28 581 km 3 from the CFM-GSFC. The discrepancy in the magnitude of the modeled FAC stems from differences in densification with depth and variations in the sensitivity of the models to atmospheric forcing. In more recent years (2005–2020), both models simulate substantial depletion of pore space. During this period, the spatially integrated FAC across the entire GrIS decreases by 3.2 % ( −66.6 km 3 yr −1 ) in SNOWPACK and 1.5 % ( ... Text Greenland Ice Sheet Sea ice Copernicus Publications: E-Journals Greenland Merra ENVELOPE(12.615,12.615,65.816,65.816) The Cryosphere 17 5 2185 2209 |
institution |
Open Polar |
collection |
Copernicus Publications: E-Journals |
op_collection_id |
ftcopernicus |
language |
English |
description |
The Greenland Ice Sheet's (GrIS) firn layer buffers the ice sheet's contribution to sea level rise by storing meltwater in its pore space. However, available pore space and meltwater retention capability is lost due to ablation of the firn layer and refreezing of meltwater as near-surface ice slabs in the firn. Understanding how firn properties respond to climate is important for constraining the GrIS's future contribution to sea level rise in a warming climate. Observations of firn density provide detailed information about firn properties, but they are spatially and temporally limited. Here we use two firn models, the physics-based SNOWPACK model and the Community Firn Model configured with a semi-empirical densification equation (CFM-GSFC), to quantify firn properties across the GrIS from 1980 through 2020. We use an identical forcing (Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2) atmospheric reanalysis) for SNOWPACK and the CFM-GSFC in order to isolate firn model differences. To evaluate the models, we compare simulated firn properties, including firn air content (FAC), to measurements from the Surface Mass Balance and Snow on Sea Ice Working Group (SUMup) dataset of snow and firn density. Both models perform well (mean absolute percentage errors of 14 % in SNOWPACK and 16 % in the CFM-GSFC), though their performance is hindered by the spatial resolution of the atmospheric forcing. In the ice-sheet-wide simulations, the 1980–1995 average spatially integrated FAC (i.e., air volume in the firn) for the upper 100 m is 34 645 km 3 from SNOWPACK and 28 581 km 3 from the CFM-GSFC. The discrepancy in the magnitude of the modeled FAC stems from differences in densification with depth and variations in the sensitivity of the models to atmospheric forcing. In more recent years (2005–2020), both models simulate substantial depletion of pore space. During this period, the spatially integrated FAC across the entire GrIS decreases by 3.2 % ( −66.6 km 3 yr −1 ) in SNOWPACK and 1.5 % ( ... |
format |
Text |
author |
Thompson-Munson, Megan Wever, Nander Stevens, C. Max Lenaerts, Jan T. M. Medley, Brooke |
spellingShingle |
Thompson-Munson, Megan Wever, Nander Stevens, C. Max Lenaerts, Jan T. M. Medley, Brooke An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
author_facet |
Thompson-Munson, Megan Wever, Nander Stevens, C. Max Lenaerts, Jan T. M. Medley, Brooke |
author_sort |
Thompson-Munson, Megan |
title |
An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
title_short |
An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
title_full |
An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
title_fullStr |
An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
title_full_unstemmed |
An evaluation of a physics-based firn model and a semi-empirical firn model across the Greenland Ice Sheet (1980–2020) |
title_sort |
evaluation of a physics-based firn model and a semi-empirical firn model across the greenland ice sheet (1980–2020) |
publishDate |
2023 |
url |
https://doi.org/10.5194/tc-17-2185-2023 https://tc.copernicus.org/articles/17/2185/2023/ |
long_lat |
ENVELOPE(12.615,12.615,65.816,65.816) |
geographic |
Greenland Merra |
geographic_facet |
Greenland Merra |
genre |
Greenland Ice Sheet Sea ice |
genre_facet |
Greenland Ice Sheet Sea ice |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-17-2185-2023 https://tc.copernicus.org/articles/17/2185/2023/ |
op_doi |
https://doi.org/10.5194/tc-17-2185-2023 |
container_title |
The Cryosphere |
container_volume |
17 |
container_issue |
5 |
container_start_page |
2185 |
op_container_end_page |
2209 |
_version_ |
1769006287112110080 |