Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking
Following the general warming trend in Greenland, an increase in calving rates, retreat and ice flow has been observed at ocean-terminating outlet glaciers. These changes contribute substantially to the current mass loss of the Greenland Ice Sheet. In order to constrain models of ice dynamics as wel...
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ftdoajarticles:oai:doaj.org/article:a6e78047ade74e01860cf13e646e997c 2023-05-15T16:21:20+02:00 Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking C. Rohner D. Small D. Henke M. P. Lüthi A. Vieli 2019-11-01T00:00:00Z https://doi.org/10.5194/tc-13-2953-2019 https://doaj.org/article/a6e78047ade74e01860cf13e646e997c EN eng Copernicus Publications https://www.the-cryosphere.net/13/2953/2019/tc-13-2953-2019.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-13-2953-2019 1994-0416 1994-0424 https://doaj.org/article/a6e78047ade74e01860cf13e646e997c The Cryosphere, Vol 13, Pp 2953-2975 (2019) Environmental sciences GE1-350 Geology QE1-996.5 article 2019 ftdoajarticles https://doi.org/10.5194/tc-13-2953-2019 2022-12-31T04:30:52Z Following the general warming trend in Greenland, an increase in calving rates, retreat and ice flow has been observed at ocean-terminating outlet glaciers. These changes contribute substantially to the current mass loss of the Greenland Ice Sheet. In order to constrain models of ice dynamics as well as estimates of mass change, detailed knowledge of geometry and ice flow is needed, in particular on the rapidly changing tongues of ocean-terminating outlet glaciers. In this study, we validate velocity estimates and spatial patterns close to the calving terminus of such an outlet derived from an iterative offset-tracking method based on synthetic aperture radar (SAR) intensity data with a collection of three independent reference measurements of glacier flow. These reference datasets are comprised of measurements from differential GPS, a terrestrial radar interferometer (TRI) and repeated unmanned aerial vehicle (UAV) surveys. Our approach to SAR velocity processing aims at achieving a relatively fine grid spacing and a high temporal resolution in order to best resolve the steep velocity gradients in the terminus area and aims to exploit the 12 d repeat interval of the single-satellite Sentinel-1A sensor. Results from images of the medium-sized ocean-terminating outlet glacier Eqip Sermia acquired by Sentinel-1A and RADARSAT-2 exhibit a mean difference of 11.5 % when compared to the corresponding GPS measurements. An areal comparison of our SAR velocity fields with independently generated velocity maps from TRI and UAV surveys showed good agreement in magnitude and spatial patterns, with mean differences smaller than 0.7 m d −1 . In comparison with existing operational velocity products, our SAR-derived velocities show an improved spatial velocity pattern near the margins and calving front. There 8 % to 30 % higher surface ice velocities are produced, which has implications on ice fluxes and on mass budget estimates of similarly sized outlet glaciers. Further, we show that offset tracking from SAR intensity data ... Article in Journal/Newspaper glacier Greenland Ice Sheet The Cryosphere Tidewater Directory of Open Access Journals: DOAJ Articles Eqip Sermia ENVELOPE(-50.067,-50.067,69.817,69.817) Greenland The Cryosphere 13 11 2953 2975 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Environmental sciences GE1-350 Geology QE1-996.5 |
spellingShingle |
Environmental sciences GE1-350 Geology QE1-996.5 C. Rohner D. Small D. Henke M. P. Lüthi A. Vieli Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
topic_facet |
Environmental sciences GE1-350 Geology QE1-996.5 |
description |
Following the general warming trend in Greenland, an increase in calving rates, retreat and ice flow has been observed at ocean-terminating outlet glaciers. These changes contribute substantially to the current mass loss of the Greenland Ice Sheet. In order to constrain models of ice dynamics as well as estimates of mass change, detailed knowledge of geometry and ice flow is needed, in particular on the rapidly changing tongues of ocean-terminating outlet glaciers. In this study, we validate velocity estimates and spatial patterns close to the calving terminus of such an outlet derived from an iterative offset-tracking method based on synthetic aperture radar (SAR) intensity data with a collection of three independent reference measurements of glacier flow. These reference datasets are comprised of measurements from differential GPS, a terrestrial radar interferometer (TRI) and repeated unmanned aerial vehicle (UAV) surveys. Our approach to SAR velocity processing aims at achieving a relatively fine grid spacing and a high temporal resolution in order to best resolve the steep velocity gradients in the terminus area and aims to exploit the 12 d repeat interval of the single-satellite Sentinel-1A sensor. Results from images of the medium-sized ocean-terminating outlet glacier Eqip Sermia acquired by Sentinel-1A and RADARSAT-2 exhibit a mean difference of 11.5 % when compared to the corresponding GPS measurements. An areal comparison of our SAR velocity fields with independently generated velocity maps from TRI and UAV surveys showed good agreement in magnitude and spatial patterns, with mean differences smaller than 0.7 m d −1 . In comparison with existing operational velocity products, our SAR-derived velocities show an improved spatial velocity pattern near the margins and calving front. There 8 % to 30 % higher surface ice velocities are produced, which has implications on ice fluxes and on mass budget estimates of similarly sized outlet glaciers. Further, we show that offset tracking from SAR intensity data ... |
format |
Article in Journal/Newspaper |
author |
C. Rohner D. Small D. Henke M. P. Lüthi A. Vieli |
author_facet |
C. Rohner D. Small D. Henke M. P. Lüthi A. Vieli |
author_sort |
C. Rohner |
title |
Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
title_short |
Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
title_full |
Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
title_fullStr |
Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
title_full_unstemmed |
Multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (SAR) intensity tracking |
title_sort |
multisensor validation of tidewater glacier flow fields derived from synthetic aperture radar (sar) intensity tracking |
publisher |
Copernicus Publications |
publishDate |
2019 |
url |
https://doi.org/10.5194/tc-13-2953-2019 https://doaj.org/article/a6e78047ade74e01860cf13e646e997c |
long_lat |
ENVELOPE(-50.067,-50.067,69.817,69.817) |
geographic |
Eqip Sermia Greenland |
geographic_facet |
Eqip Sermia Greenland |
genre |
glacier Greenland Ice Sheet The Cryosphere Tidewater |
genre_facet |
glacier Greenland Ice Sheet The Cryosphere Tidewater |
op_source |
The Cryosphere, Vol 13, Pp 2953-2975 (2019) |
op_relation |
https://www.the-cryosphere.net/13/2953/2019/tc-13-2953-2019.pdf https://doaj.org/toc/1994-0416 https://doaj.org/toc/1994-0424 doi:10.5194/tc-13-2953-2019 1994-0416 1994-0424 https://doaj.org/article/a6e78047ade74e01860cf13e646e997c |
op_doi |
https://doi.org/10.5194/tc-13-2953-2019 |
container_title |
The Cryosphere |
container_volume |
13 |
container_issue |
11 |
container_start_page |
2953 |
op_container_end_page |
2975 |
_version_ |
1766009337643270144 |