On the use of radar altimetry to study the snow of the Antarctic ice-sheet
The Antarctic ice-sheet is composed by a thick layer of ice surmounted by firn of up to 100 m thick. For now almost 40 years, the satellite observations provide a great number of information on its topography and some properties of the snow surface. However, the knowledge of its shallow and deeper s...
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Other Authors: | , , , , , |
Format: | Doctoral or Postdoctoral Thesis |
Language: | French |
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HAL CCSD
2007
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Online Access: | https://theses.hal.science/tel-00216105 https://theses.hal.science/tel-00216105/document https://theses.hal.science/tel-00216105/file/manuscript.pdf |
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ftmeteofrance:oai:HAL:tel-00216105v1 |
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record_format |
openpolar |
institution |
Open Polar |
collection |
Météo-France: HAL |
op_collection_id |
ftmeteofrance |
language |
French |
topic |
snow properties remote sensing radar altimetry radar modelling Antarctic ice-sheet calotte polaire Antarctique propriétés de la neige compaction télédétection altimétrie radar modélisation radar [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
spellingShingle |
snow properties remote sensing radar altimetry radar modelling Antarctic ice-sheet calotte polaire Antarctique propriétés de la neige compaction télédétection altimétrie radar modélisation radar [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere Lacroix, Pascal On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
topic_facet |
snow properties remote sensing radar altimetry radar modelling Antarctic ice-sheet calotte polaire Antarctique propriétés de la neige compaction télédétection altimétrie radar modélisation radar [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere |
description |
The Antarctic ice-sheet is composed by a thick layer of ice surmounted by firn of up to 100 m thick. For now almost 40 years, the satellite observations provide a great number of information on its topography and some properties of the snow surface. However, the knowledge of its shallow and deeper snowpack properties is still very limited. The snow precipitations are transported and deposed by the wind to form layers. The successive accumulations of snow bury the snow layers, which are modified under the temperature and pressure conditions. Yet, the accumulation rate or the snow grain size are important climate indicators, not well known, whom signatures are contained in the near-surface observations. Since 2002, the ENVISAT satellite provides altimetric data over 80 \% of the Antarctic ice-sheet simultaneously at 2 different frequencies (S band at 3.2 GHz and Ku band at 13.6 GHz). These two waves penetrate into the snowpack over several meters and are reflected differently by its different elements, depending on the frequency. The idea of this thesis is therefore to use the dual frequency information to retrieve properties of the snowpack. We solve this problematic by an analysis and a modelling of the dual frequency altimetric signal over the ice-sheet, and then by its inversion. We focus first on different case studies to estimate the sensitivity of these signals to different properties of the snow: i/ the altimetric signal is sensitive to the snow surface roughness at different scales, ii/ the altimetric signal varies seasonally under compaction of the near-surface snow, iii/ the radar waves are reflected by deep layers of ice or snow. A model of altimetric signal is developed to compare the two frequency datasets over the whole ice-sheet. The results of the model are used to explain the seasonal variations previously observed. These results provide the first observations of the seasonal compaction of the snowpack. Finally, the snowpack properties are estimated at a global scale over the Antarctic ice-sheet. ... |
author2 |
Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) Université Paul Sabatier - Toulouse III Frédérique Rémy et Monique Dechambre |
format |
Doctoral or Postdoctoral Thesis |
author |
Lacroix, Pascal |
author_facet |
Lacroix, Pascal |
author_sort |
Lacroix, Pascal |
title |
On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
title_short |
On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
title_full |
On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
title_fullStr |
On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
title_full_unstemmed |
On the use of radar altimetry to study the snow of the Antarctic ice-sheet |
title_sort |
on the use of radar altimetry to study the snow of the antarctic ice-sheet |
publisher |
HAL CCSD |
publishDate |
2007 |
url |
https://theses.hal.science/tel-00216105 https://theses.hal.science/tel-00216105/document https://theses.hal.science/tel-00216105/file/manuscript.pdf |
genre |
Antarc* Antarctic Antarctique* Ice Sheet |
genre_facet |
Antarc* Antarctic Antarctique* Ice Sheet |
op_source |
https://theses.hal.science/tel-00216105 Océan, Atmosphère. Université Paul Sabatier - Toulouse III, 2007. Français. ⟨NNT : ⟩ |
op_relation |
tel-00216105 https://theses.hal.science/tel-00216105 https://theses.hal.science/tel-00216105/document https://theses.hal.science/tel-00216105/file/manuscript.pdf |
op_rights |
info:eu-repo/semantics/OpenAccess |
_version_ |
1810289534538088448 |
spelling |
ftmeteofrance:oai:HAL:tel-00216105v1 2024-09-15T17:48:23+00:00 On the use of radar altimetry to study the snow of the Antarctic ice-sheet Apport de l'altimétrie radar spatiale à l'étude de la neige de la calotte polaire Antarctique Lacroix, Pascal Laboratoire d'études en Géophysique et océanographie spatiales (LEGOS) Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP) Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales Toulouse (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France-Centre National de la Recherche Scientifique (CNRS) Université Paul Sabatier - Toulouse III Frédérique Rémy et Monique Dechambre 2007-10-04 https://theses.hal.science/tel-00216105 https://theses.hal.science/tel-00216105/document https://theses.hal.science/tel-00216105/file/manuscript.pdf fr fre HAL CCSD tel-00216105 https://theses.hal.science/tel-00216105 https://theses.hal.science/tel-00216105/document https://theses.hal.science/tel-00216105/file/manuscript.pdf info:eu-repo/semantics/OpenAccess https://theses.hal.science/tel-00216105 Océan, Atmosphère. Université Paul Sabatier - Toulouse III, 2007. Français. ⟨NNT : ⟩ snow properties remote sensing radar altimetry radar modelling Antarctic ice-sheet calotte polaire Antarctique propriétés de la neige compaction télédétection altimétrie radar modélisation radar [SDU.OCEAN]Sciences of the Universe [physics]/Ocean Atmosphere info:eu-repo/semantics/doctoralThesis Theses 2007 ftmeteofrance 2024-06-25T00:18:08Z The Antarctic ice-sheet is composed by a thick layer of ice surmounted by firn of up to 100 m thick. For now almost 40 years, the satellite observations provide a great number of information on its topography and some properties of the snow surface. However, the knowledge of its shallow and deeper snowpack properties is still very limited. The snow precipitations are transported and deposed by the wind to form layers. The successive accumulations of snow bury the snow layers, which are modified under the temperature and pressure conditions. Yet, the accumulation rate or the snow grain size are important climate indicators, not well known, whom signatures are contained in the near-surface observations. Since 2002, the ENVISAT satellite provides altimetric data over 80 \% of the Antarctic ice-sheet simultaneously at 2 different frequencies (S band at 3.2 GHz and Ku band at 13.6 GHz). These two waves penetrate into the snowpack over several meters and are reflected differently by its different elements, depending on the frequency. The idea of this thesis is therefore to use the dual frequency information to retrieve properties of the snowpack. We solve this problematic by an analysis and a modelling of the dual frequency altimetric signal over the ice-sheet, and then by its inversion. We focus first on different case studies to estimate the sensitivity of these signals to different properties of the snow: i/ the altimetric signal is sensitive to the snow surface roughness at different scales, ii/ the altimetric signal varies seasonally under compaction of the near-surface snow, iii/ the radar waves are reflected by deep layers of ice or snow. A model of altimetric signal is developed to compare the two frequency datasets over the whole ice-sheet. The results of the model are used to explain the seasonal variations previously observed. These results provide the first observations of the seasonal compaction of the snowpack. Finally, the snowpack properties are estimated at a global scale over the Antarctic ice-sheet. ... Doctoral or Postdoctoral Thesis Antarc* Antarctic Antarctique* Ice Sheet Météo-France: HAL |