| Titre | A revised calibration of the interferometric mode of the CryoSat-2 radar altimeter improves ice height and height change measurements in western Greenland |
| Auteur | Gray, L; Burgess, D ; Copland, L; Dunse, T; Langley, K; Moholdt, G |
| Source | The Cryosphere 11, 2017 p. 1041-1058, https://doi.org/10.5194/tc-11-1041-2017  Accès ouvert |
| Image |  |
| Année | 2017 |
| Séries alt. | Secteur des sciences de la Terre, Contribution externe 20160331 |
| Éditeur | Copernicus GmbH |
| Document | publication en série |
| Lang. | anglais |
| DOI | https://doi.org/10.5194/tc-11-1041-2017 |
| Media | papier; en ligne; numérique |
| Formats | pdf |
| Province | Nunavut |
| SNRC | 48E/09; 48E/10; 48E/11; 48E/12; 48E/13; 48E/14; 48E/15; 48E/16; 48F/09; 48F/16; 48G/01; 48G/08; 48G/09; 48G/16; 48H |
| Région | Devon Ice Cap; Jakobshavn Glacier |
| Lat/Long OENS | -85.0000 -80.0000 75.8000 74.8000 |
| Lat/Long OENS | -51.0000 -47.0000 71.2500 67.5000 |
| Sujets | glaciologie; champs de glace; glaciers; ablation; lacs glaciaires; télédétection; imagerie par satellite; imagerie radar; méthodes radar; SARS; méthodologie; géologie des dépôts meubles/géomorphologie;
géophysique; Nature et environnement |
| Illustrations | tableaux; cartes de localisation; images satellitaires; graphiques; histogrammes |
| Programme | Géosciences de changements climatiques, Surveillance des variables climatiques |
| Programme | Programme du plateau continental polaire |
| Diffusé | 2016 12 21 |
| Résumé | (disponible en anglais seulement)
We compare geocoded heights derived from the interferometric mode (SARIn) of CryoSat to surface heights from calibration-validation sites on Devon Ice Cap and
West Greenland. Comparisons are included for both the heights derived from the first return (the 'point-of-closest-approach' or POCA) as well as heights derived from delayed waveform returns ('swath' processing). While swath processed heights are
normally less accurate than edited POCA heights, of order 1 - 5 m instead of order 1- 2 m, the increased coverage possible with swath data complements the POCA data and provides useful information for both system calibration and improving digital
elevation models (DEMs). We show that the pre-launch interferometric baseline coupled with an additional roll correction (~0.0075°), or equivalent phase correction (~0.0435 radians), provides an improved calibration of the interferometric SARIn
mode.
We extend the potential use of SARIn data by showing the influence of surface conditions, especially melt, on the return waveforms, and that it is possible to detect and measure the height of summer supraglacial lakes in West Greenland. A
supraglacial lake can provide a strong radar target in the waveform, stronger than the initial POCA return, if viewed at near normal incidence. This provides an ideal situation for swath processing and we demonstrate height accuracies of ~ 0.5 m for
two lake sites, one in the accumulation zone and one in the ablation zone, which were measured every year from 2010 or 2011 to 2016. Each year the lake in the ablation zone was viewed in June by ascending passes and then 5.5 days later by descending
passes which allows an approximate estimate of the filling rate. The results suggest that CryoSat waveform data and measurements of supraglacial lake height change could complement the use of optical satellite and be helpful as proxy indicators for
surface melt around Greenland. |
| Sommaire | (Résumé en langage clair et simple, non publié)
L'altimètre radar CryoSat est une initiative de l'Agence spatiale européenne qui jouera un rôle essentiel dans l'approche d'observation du
climat glaciaire au Canada, contribuant aux objectifs du programme de géosciences du changement climatique en fournissant des données sur le changement de masse des glaciers en ce qui concerne le flux d'eau douce vers les océans. Dans cet article
scientifique, des améliorations à la performance de CryoSat-2 sont faites en ajustant le pré-calibrage de l'angle de roulis et en validant la surface de la calotte glaciaire et l'interprétation des formes d'onde de radar en faible profondeur sous
la surface. Nous montrons que CryoSat-2 est efficace pour mesurer des changements de hauteur des lacs supraglaciaires sur le Groenland comme indicateurs potentiellement utiles du changement climatique. Des mesures semblables seront faites sur les
calottes glaciaires canadiennes dans les études futures. |
| GEOSCAN ID | 299672 |
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