The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters
Satellite radar altimeters are being used to measure ice sheet mass balance by detecting changes in surface elevation. Climate variability may cause errors in these measurements by altering the structure of the snow and the penetration of the radar pulse. Three parameters describe the microwave pene...
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ftucl:oai:eprints.ucl.ac.uk.OAI2:10097275 2023-12-24T10:08:46+01:00 The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters Arthern, Robert James 1997 text https://discovery.ucl.ac.uk/id/eprint/10097275/1/out.pdf https://discovery.ucl.ac.uk/id/eprint/10097275/ eng eng UCL (University College London) https://discovery.ucl.ac.uk/id/eprint/10097275/1/out.pdf https://discovery.ucl.ac.uk/id/eprint/10097275/ open Doctoral thesis, UCL (University College London). Applied sciences Earth sciences Balance Climate Ice-sheet mass Satellite radar altimeters Variability Weather Thesis Doctoral 1997 ftucl 2023-11-27T13:07:34Z Satellite radar altimeters are being used to measure ice sheet mass balance by detecting changes in surface elevation. Climate variability may cause errors in these measurements by altering the structure of the snow and the penetration of the radar pulse. Three parameters describe the microwave penetration and scattering; the surface backscatter σ°surf, the volume backscatter σ°vol, the extinction coefficient ke, These parameters were measured in Antarctica using ERS-1 altimeter data and compared with satellite radiometer data, glaciological observations, and a scattering model, to determine the sensitivity of the radar echo to the snow structure. Echo distortion, caused by topographic undulations, limits the accuracy of σ°surf, σ°vol, and ke. In flatter regions though, the retrieval shows that reflections at layer interfaces beneath the surface generally account for most of the backscatter. Surface reflection can cause 60% of the backscatter in low accumulation regions prone to surface crusts. Only about 1% of the total backscatter arises from volume scattering by snow grains, although this mechanism controls the magnitude of ke. Only σ°surf changes on monthly timescales, through changes in the roughness and density of the surface snow. However, because of an anisotropy in snow structure in windy regions, ke and σ°vol depend upon the direction of travel of the satellite, which may vary between measurements. The sensitivity of ke and σ°vol to changes in accumulation rate, temperature and density is investigated, and used to calculate the errors in the mass balance which might be expected for measurement intervals of many years, and also to map accumulation rates on the plateau. By changing the rate of snow compaction, the meteorological boundary conditions can also alter the average density of the ice sheets, causing further errors in the mass balance measurement. A numerical model of time-variant snow densification was used to calculate the errors from this source. Overall, it is concluded that satellite radar ... Doctoral or Postdoctoral Thesis Antarc* Antarctica Ice Sheet University College London: UCL Discovery |
institution |
Open Polar |
collection |
University College London: UCL Discovery |
op_collection_id |
ftucl |
language |
English |
topic |
Applied sciences Earth sciences Balance Climate Ice-sheet mass Satellite radar altimeters Variability Weather |
spellingShingle |
Applied sciences Earth sciences Balance Climate Ice-sheet mass Satellite radar altimeters Variability Weather Arthern, Robert James The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
topic_facet |
Applied sciences Earth sciences Balance Climate Ice-sheet mass Satellite radar altimeters Variability Weather |
description |
Satellite radar altimeters are being used to measure ice sheet mass balance by detecting changes in surface elevation. Climate variability may cause errors in these measurements by altering the structure of the snow and the penetration of the radar pulse. Three parameters describe the microwave penetration and scattering; the surface backscatter σ°surf, the volume backscatter σ°vol, the extinction coefficient ke, These parameters were measured in Antarctica using ERS-1 altimeter data and compared with satellite radiometer data, glaciological observations, and a scattering model, to determine the sensitivity of the radar echo to the snow structure. Echo distortion, caused by topographic undulations, limits the accuracy of σ°surf, σ°vol, and ke. In flatter regions though, the retrieval shows that reflections at layer interfaces beneath the surface generally account for most of the backscatter. Surface reflection can cause 60% of the backscatter in low accumulation regions prone to surface crusts. Only about 1% of the total backscatter arises from volume scattering by snow grains, although this mechanism controls the magnitude of ke. Only σ°surf changes on monthly timescales, through changes in the roughness and density of the surface snow. However, because of an anisotropy in snow structure in windy regions, ke and σ°vol depend upon the direction of travel of the satellite, which may vary between measurements. The sensitivity of ke and σ°vol to changes in accumulation rate, temperature and density is investigated, and used to calculate the errors in the mass balance which might be expected for measurement intervals of many years, and also to map accumulation rates on the plateau. By changing the rate of snow compaction, the meteorological boundary conditions can also alter the average density of the ice sheets, causing further errors in the mass balance measurement. A numerical model of time-variant snow densification was used to calculate the errors from this source. Overall, it is concluded that satellite radar ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Arthern, Robert James |
author_facet |
Arthern, Robert James |
author_sort |
Arthern, Robert James |
title |
The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
title_short |
The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
title_full |
The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
title_fullStr |
The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
title_full_unstemmed |
The impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
title_sort |
impact of weather and climate variability upon estimates of ice-sheet mass balance from satellite radar altimeters |
publisher |
UCL (University College London) |
publishDate |
1997 |
url |
https://discovery.ucl.ac.uk/id/eprint/10097275/1/out.pdf https://discovery.ucl.ac.uk/id/eprint/10097275/ |
genre |
Antarc* Antarctica Ice Sheet |
genre_facet |
Antarc* Antarctica Ice Sheet |
op_source |
Doctoral thesis, UCL (University College London). |
op_relation |
https://discovery.ucl.ac.uk/id/eprint/10097275/1/out.pdf https://discovery.ucl.ac.uk/id/eprint/10097275/ |
op_rights |
open |
_version_ |
1786203603690586112 |