An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data
Radar inference of the bulk properties of glacier beds, most notably identifying basal melting, is, in general, derived from the basal reflection coefficient. On the scale of an ice sheet, unambiguous determination of basal reflection is primarily limited by uncertainty in the englacial attenuation...
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ftcopernicus:oai:publications.copernicus.org:tc49396 2023-05-15T16:03:05+02:00 An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data Jordan, T. M. Bamber, J. L. Williams, C. N. Paden, J. D. Siegert, M. J. Huybrechts, P. Gagliardini, O. Gillet-Chaulet, F. 2018-09-27 application/pdf https://doi.org/10.5194/tc-10-1547-2016 https://tc.copernicus.org/articles/10/1547/2016/ eng eng doi:10.5194/tc-10-1547-2016 https://tc.copernicus.org/articles/10/1547/2016/ eISSN: 1994-0424 Text 2018 ftcopernicus https://doi.org/10.5194/tc-10-1547-2016 2020-07-20T16:24:03Z Radar inference of the bulk properties of glacier beds, most notably identifying basal melting, is, in general, derived from the basal reflection coefficient. On the scale of an ice sheet, unambiguous determination of basal reflection is primarily limited by uncertainty in the englacial attenuation of the radio wave, which is an Arrhenius function of temperature. Existing bed-returned power algorithms for deriving attenuation assume that the attenuation rate is regionally constant, which is not feasible at an ice-sheet-wide scale. Here we introduce a new semi-empirical framework for deriving englacial attenuation, and, to demonstrate its efficacy, we apply it to the Greenland Ice Sheet. A central feature is the use of a prior Arrhenius temperature model to estimate the spatial variation in englacial attenuation as a first guess input for the radar algorithm. We demonstrate regions of solution convergence for two input temperature fields and for independently analysed field campaigns. The coverage achieved is a trade-off with uncertainty and we propose that the algorithm can be "tuned" for discrimination of basal melt (attenuation loss uncertainty ∼ 5 dB). This is supported by our physically realistic ( ∼ 20 dB) range for the basal reflection coefficient. Finally, we show that the attenuation solution can be used to predict the temperature bias of thermomechanical ice sheet models and is in agreement with known model temperature biases at the Dye 3 ice core. Text Dye 3 Dye-3 glacier Greenland ice core Ice Sheet Copernicus Publications: E-Journals Greenland The Cryosphere 10 4 1547 1570 |
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Open Polar |
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Copernicus Publications: E-Journals |
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ftcopernicus |
language |
English |
description |
Radar inference of the bulk properties of glacier beds, most notably identifying basal melting, is, in general, derived from the basal reflection coefficient. On the scale of an ice sheet, unambiguous determination of basal reflection is primarily limited by uncertainty in the englacial attenuation of the radio wave, which is an Arrhenius function of temperature. Existing bed-returned power algorithms for deriving attenuation assume that the attenuation rate is regionally constant, which is not feasible at an ice-sheet-wide scale. Here we introduce a new semi-empirical framework for deriving englacial attenuation, and, to demonstrate its efficacy, we apply it to the Greenland Ice Sheet. A central feature is the use of a prior Arrhenius temperature model to estimate the spatial variation in englacial attenuation as a first guess input for the radar algorithm. We demonstrate regions of solution convergence for two input temperature fields and for independently analysed field campaigns. The coverage achieved is a trade-off with uncertainty and we propose that the algorithm can be "tuned" for discrimination of basal melt (attenuation loss uncertainty ∼ 5 dB). This is supported by our physically realistic ( ∼ 20 dB) range for the basal reflection coefficient. Finally, we show that the attenuation solution can be used to predict the temperature bias of thermomechanical ice sheet models and is in agreement with known model temperature biases at the Dye 3 ice core. |
format |
Text |
author |
Jordan, T. M. Bamber, J. L. Williams, C. N. Paden, J. D. Siegert, M. J. Huybrechts, P. Gagliardini, O. Gillet-Chaulet, F. |
spellingShingle |
Jordan, T. M. Bamber, J. L. Williams, C. N. Paden, J. D. Siegert, M. J. Huybrechts, P. Gagliardini, O. Gillet-Chaulet, F. An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
author_facet |
Jordan, T. M. Bamber, J. L. Williams, C. N. Paden, J. D. Siegert, M. J. Huybrechts, P. Gagliardini, O. Gillet-Chaulet, F. |
author_sort |
Jordan, T. M. |
title |
An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
title_short |
An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
title_full |
An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
title_fullStr |
An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
title_full_unstemmed |
An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
title_sort |
ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data |
publishDate |
2018 |
url |
https://doi.org/10.5194/tc-10-1547-2016 https://tc.copernicus.org/articles/10/1547/2016/ |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
Dye 3 Dye-3 glacier Greenland ice core Ice Sheet |
genre_facet |
Dye 3 Dye-3 glacier Greenland ice core Ice Sheet |
op_source |
eISSN: 1994-0424 |
op_relation |
doi:10.5194/tc-10-1547-2016 https://tc.copernicus.org/articles/10/1547/2016/ |
op_doi |
https://doi.org/10.5194/tc-10-1547-2016 |
container_title |
The Cryosphere |
container_volume |
10 |
container_issue |
4 |
container_start_page |
1547 |
op_container_end_page |
1570 |
_version_ |
1766398718997692416 |