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 extrac...
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ftboisestateu:oai:scholarworks.boisestate.edu:cgiss_facpubs-1152 2023-10-29T02:36:42+01:00 Georadar-Derived Estimates of Firn Density in the Percolation Zone, Western Greenland Ice Sheet Brown, Joel Bradford, John Harper, Joel Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen 2012-01-25T08:00:00Z application/pdf https://scholarworks.boisestate.edu/cgiss_facpubs/153 https://scholarworks.boisestate.edu/context/cgiss_facpubs/article/1152/viewcontent/Bradford___Georadar_derived_estimates.pdf unknown ScholarWorks https://scholarworks.boisestate.edu/cgiss_facpubs/153 https://scholarworks.boisestate.edu/context/cgiss_facpubs/article/1152/viewcontent/Bradford___Georadar_derived_estimates.pdf Copyright 2012 by the American Geophysical Union. DOI: 10.1029/2011jf002089 CGISS Publications and Presentations Geosciences Earth Sciences Geophysics and Seismology text 2012 ftboisestateu 2023-09-29T15:08:27Z 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 georadar to investigate firn density variations with depth along a ~70 km transect through a portion of the accumulation area in western Greenland that partially melts. We estimated electromagnetic wave velocity by inverting reflection traveltimes 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 Boise State University: Scholar Works |
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Boise State University: Scholar Works |
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Geosciences Earth Sciences Geophysics and Seismology |
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Geosciences Earth Sciences Geophysics and Seismology Brown, Joel Bradford, John Harper, Joel Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen Georadar-Derived Estimates of Firn Density in the Percolation Zone, Western Greenland Ice Sheet |
topic_facet |
Geosciences Earth Sciences Geophysics and Seismology |
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 georadar to investigate firn density variations with depth along a ~70 km transect through a portion of the accumulation area in western Greenland that partially melts. We estimated electromagnetic wave velocity by inverting reflection traveltimes 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 Pfeffer, W. Tad Humphrey, Neil Mosley-Thompson, Ellen |
author_facet |
Brown, Joel Bradford, John Harper, Joel 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 |
publishDate |
2012 |
url |
https://scholarworks.boisestate.edu/cgiss_facpubs/153 https://scholarworks.boisestate.edu/context/cgiss_facpubs/article/1152/viewcontent/Bradford___Georadar_derived_estimates.pdf |
genre |
Greenland Ice Sheet |
genre_facet |
Greenland Ice Sheet |
op_source |
CGISS Publications and Presentations |
op_relation |
https://scholarworks.boisestate.edu/cgiss_facpubs/153 https://scholarworks.boisestate.edu/context/cgiss_facpubs/article/1152/viewcontent/Bradford___Georadar_derived_estimates.pdf |
op_rights |
Copyright 2012 by the American Geophysical Union. DOI: 10.1029/2011jf002089 |
_version_ |
1781060778566090752 |