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...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-07-01
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| Series: | The Cryosphere |
| Online Access: | http://www.the-cryosphere.net/10/1547/2016/tc-10-1547-2016.pdf |
| _version_ | 1811312150140944384 |
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| author | T. M. Jordan J. L. Bamber C. N. Williams J. D. Paden M. J. Siegert P. Huybrechts O. Gagliardini F. Gillet-Chaulet |
| author_facet | T. M. Jordan J. L. Bamber C. N. Williams J. D. Paden M. J. Siegert P. Huybrechts O. Gagliardini F. Gillet-Chaulet |
| author_sort | T. M. Jordan |
| collection | DOAJ |
| 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. |
| first_indexed | 2024-04-13T10:32:16Z |
| format | Article |
| id | doaj.art-005b41a181ae4a1490d1be5ef286ec7c |
| institution | Directory Open Access Journal |
| issn | 1994-0416 1994-0424 |
| language | English |
| last_indexed | 2024-04-13T10:32:16Z |
| publishDate | 2016-07-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | The Cryosphere |
| spelling | doaj.art-005b41a181ae4a1490d1be5ef286ec7c2022-12-22T02:50:09ZengCopernicus PublicationsThe Cryosphere1994-04161994-04242016-07-011041547157010.5194/tc-10-1547-2016An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar dataT. M. Jordan0J. L. Bamber1C. N. Williams2J. D. Paden3M. J. Siegert4P. Huybrechts5O. Gagliardini6F. Gillet-Chaulet7Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UKBristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UKBristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, UKCenter for Remote Sensing of Ice Sheets, University of Kansas, Lawrence, USAGrantham Institute and Earth Science and Engineering, Imperial College, University of London, London, UKEarth System Science and Departement Geografie, Vrije Universiteit Brussel, Brussels, BelgiumLe Laboratoire de Glaciologie et Geophysique de l'Environnement, University Grenoble Alpes, Grenoble, FranceLe Laboratoire de Glaciologie et Geophysique de l'Environnement, Centre National de la Recherche Scientifique, Grenoble, FranceRadar 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.http://www.the-cryosphere.net/10/1547/2016/tc-10-1547-2016.pdf |
| spellingShingle | T. M. Jordan J. L. Bamber C. N. Williams J. D. Paden M. J. Siegert P. Huybrechts O. Gagliardini F. Gillet-Chaulet An ice-sheet-wide framework for englacial attenuation from ice-penetrating radar data The Cryosphere |
| title | 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_short | 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 |
| url | http://www.the-cryosphere.net/10/1547/2016/tc-10-1547-2016.pdf |
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