Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet
Greater understanding of variations in firn densification is needed to distinguish between dynamic and melt-driven elevation changes on the Greenland ice sheet. This is especially true in Greenland’s percolation zone, where firn density profiles are poorly documented because few ice cores are extr...
Published in: | Journal of Geophysical Research: Earth Surface |
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ScholarWorks at University of Montana
2012
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Online Access: | https://scholarworks.umt.edu/geosci_pubs/14 https://doi.org/10.1029/2011JF002089 https://scholarworks.umt.edu/context/geosci_pubs/article/1016/viewcontent/Brown_et_al_2012_Journal_of_Geophysical_Research__Earth_Surface__2003_2012_.pdf https://scholarworks.umt.edu/context/geosci_pubs/article/1016/filename/0/type/additional/viewcontent/Suppl_for_Brown_et_all_2012_Journal_of_Geophysical_Research.pdf |
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ftunivmontana:oai:scholarworks.umt.edu:geosci_pubs-1016 2024-09-09T19:42:53+00:00 Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet Brown, Joel Bradford, John Harper, Joel T. Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen 2012-01-25T08:00:00Z application/pdf https://scholarworks.umt.edu/geosci_pubs/14 https://doi.org/10.1029/2011JF002089 https://scholarworks.umt.edu/context/geosci_pubs/article/1016/viewcontent/Brown_et_al_2012_Journal_of_Geophysical_Research__Earth_Surface__2003_2012_.pdf https://scholarworks.umt.edu/context/geosci_pubs/article/1016/filename/0/type/additional/viewcontent/Suppl_for_Brown_et_all_2012_Journal_of_Geophysical_Research.pdf unknown ScholarWorks at University of Montana https://scholarworks.umt.edu/geosci_pubs/14 doi:10.1029/2011JF002089 https://scholarworks.umt.edu/context/geosci_pubs/article/1016/viewcontent/Brown_et_al_2012_Journal_of_Geophysical_Research__Earth_Surface__2003_2012_.pdf https://scholarworks.umt.edu/context/geosci_pubs/article/1016/filename/0/type/additional/viewcontent/Suppl_for_Brown_et_all_2012_Journal_of_Geophysical_Research.pdf © 2012. American Geophysical Union. Geosciences Faculty Publications Earth Sciences Geology text 2012 ftunivmontana https://doi.org/10.1029/2011JF002089 2024-06-20T05:32:53Z Greater understanding of variations in firn densification is needed to distinguish between dynamic and melt-driven elevation changes on the Greenland ice sheet. This is especially true in Greenland’s percolation zone, where firn density profiles are poorly documented because few ice cores are extracted in regions with surface melt.We used geoader to investigate firn density variations with depth along an about 70 km transect through a portion of the accumulation area in western Greenland that partially melts. We estimated electromagnetic wave velocity by inverting reflection travel times picked from common midpoint gathers. We followed a procedure designed to find the simplest velocity versus depth model that describes the data within estimated uncertainty. On the basis of the velocities, we estimated 13 depth-density profiles of the upper 80 m using a petrophysical model based on the complex refractive index method equation. At the highest elevation site, our density profile is consistent with nearby core data acquired in the same year. Our profiles at the six highest elevation sites match an empirically based densification model for dry firn, indicating relatively minor amounts of water infiltration and densification by melt and refreeze in this higher region of the percolation zone. At the four lowest elevation sites our profiles reach ice densities at substantially shallower depths, implying considerable meltwater infiltration and ice layer development in this lower region of the percolation zone. The separation between these two regions is 8 km and spans 60 m of elevation, which suggests that the balance between dry-firn and melt-induced densification processes is sensitive to minor changes in melt. Text Greenland Ice Sheet University of Montana: ScholarWorks Greenland Journal of Geophysical Research: Earth Surface 117 F1 n/a n/a |
institution |
Open Polar |
collection |
University of Montana: ScholarWorks |
op_collection_id |
ftunivmontana |
language |
unknown |
topic |
Earth Sciences Geology |
spellingShingle |
Earth Sciences Geology Brown, Joel Bradford, John Harper, Joel T. Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
topic_facet |
Earth Sciences Geology |
description |
Greater understanding of variations in firn densification is needed to distinguish between dynamic and melt-driven elevation changes on the Greenland ice sheet. This is especially true in Greenland’s percolation zone, where firn density profiles are poorly documented because few ice cores are extracted in regions with surface melt.We used geoader to investigate firn density variations with depth along an about 70 km transect through a portion of the accumulation area in western Greenland that partially melts. We estimated electromagnetic wave velocity by inverting reflection travel times picked from common midpoint gathers. We followed a procedure designed to find the simplest velocity versus depth model that describes the data within estimated uncertainty. On the basis of the velocities, we estimated 13 depth-density profiles of the upper 80 m using a petrophysical model based on the complex refractive index method equation. At the highest elevation site, our density profile is consistent with nearby core data acquired in the same year. Our profiles at the six highest elevation sites match an empirically based densification model for dry firn, indicating relatively minor amounts of water infiltration and densification by melt and refreeze in this higher region of the percolation zone. At the four lowest elevation sites our profiles reach ice densities at substantially shallower depths, implying considerable meltwater infiltration and ice layer development in this lower region of the percolation zone. The separation between these two regions is 8 km and spans 60 m of elevation, which suggests that the balance between dry-firn and melt-induced densification processes is sensitive to minor changes in melt. |
format |
Text |
author |
Brown, Joel Bradford, John Harper, Joel T. Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen |
author_facet |
Brown, Joel Bradford, John Harper, Joel T. Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen |
author_sort |
Brown, Joel |
title |
Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
title_short |
Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
title_full |
Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
title_fullStr |
Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
title_full_unstemmed |
Georadar-derived estimates of firn density in the percolation zone, western Greenland ice sheet |
title_sort |
georadar-derived estimates of firn density in the percolation zone, western greenland ice sheet |
publisher |
ScholarWorks at University of Montana |
publishDate |
2012 |
url |
https://scholarworks.umt.edu/geosci_pubs/14 https://doi.org/10.1029/2011JF002089 https://scholarworks.umt.edu/context/geosci_pubs/article/1016/viewcontent/Brown_et_al_2012_Journal_of_Geophysical_Research__Earth_Surface__2003_2012_.pdf https://scholarworks.umt.edu/context/geosci_pubs/article/1016/filename/0/type/additional/viewcontent/Suppl_for_Brown_et_all_2012_Journal_of_Geophysical_Research.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
Geosciences Faculty Publications |
op_relation |
https://scholarworks.umt.edu/geosci_pubs/14 doi:10.1029/2011JF002089 https://scholarworks.umt.edu/context/geosci_pubs/article/1016/viewcontent/Brown_et_al_2012_Journal_of_Geophysical_Research__Earth_Surface__2003_2012_.pdf https://scholarworks.umt.edu/context/geosci_pubs/article/1016/filename/0/type/additional/viewcontent/Suppl_for_Brown_et_all_2012_Journal_of_Geophysical_Research.pdf |
op_rights |
© 2012. American Geophysical Union. |
op_doi |
https://doi.org/10.1029/2011JF002089 |
container_title |
Journal of Geophysical Research: Earth Surface |
container_volume |
117 |
container_issue |
F1 |
container_start_page |
n/a |
op_container_end_page |
n/a |
_version_ |
1809912188128722944 |