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Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling. / Helena Juliet Sykes

Swansea University Author: Helena Juliet Sykes

Abstract

The Rutford and Evans Ice Streams together drain over 150,000 km2 of the West Antarctic Ice Sheet, a marine ice sheet with much of its bed below sea level. Ice streams make up only 13% of the Antarctic coastline, but are responsible for 90% of the discharge across the grounding line, where the ice s...

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Published: 2009
Institution: Swansea University
Degree level: Doctoral
Degree name: Ph.D
URI: https://cronfa.swan.ac.uk/Record/cronfa42575
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spelling 2018-08-02T16:24:29.7121972 v2 42575 2018-08-02 Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling. ad32695f7020ebccd3f083fdc4434540 NULL Helena Juliet Sykes Helena Juliet Sykes true true 2018-08-02 The Rutford and Evans Ice Streams together drain over 150,000 km2 of the West Antarctic Ice Sheet, a marine ice sheet with much of its bed below sea level. Ice streams make up only 13% of the Antarctic coastline, but are responsible for 90% of the discharge across the grounding line, where the ice starts to float. The Rutford and Evans Ice Streams were investigated using the remote sensing method of interferometry, which uses the phase difference between successive Synthetic Aperture Radar (SAR) satellite images to derive displacement in the line-of-sight (LOS) direction of the satellite and topography, which can be separated with further processing. The grounding zones of both ice streams were mapped from clearly defined changes in vertical tidal motion visible in the interferograms. The Rutford grounding zone is dominated by a central pinning point, and the Evans grounding zone has a complex shape so that for much of the main trunk of the ice stream the east side is grounded and the west side is floating. The tidal signal for each ice stream was reconstructed, and the tidal ranges of the Rutford and Evans grounding zones are more than 6 m and 5 m respectively, both well above average for Antarctica. Vertical displacement observed in both single and double difference interferograms correlated well to changing tidal height. The width of the grounding zone modelled using an elastic beam was close to the observed grounding zone width for both ice streams. Successful differential interferometry relies on the validity of the Constant Velocity Assumption (CVA), which states that interferograms differenced to derive topographic phase must contain the same displacement phase. However, due to the large tidal ranges at the grounding lines both ice streams, this assumption, which would be better termed the Constant Displacement Assumption (CDA), was violated to an extent which may be unprecedented in the literature. The Rutford Ice Stream reached velocities of approximately 400 m a-1 at its grounding line between 1992 and 1996, and the Evans Ice Stream appears to have decreased in speed from 750 m a-1 in 1992 to 540 m a-1 in 1996. This would have a significant effect on mass balance. The behaviour of this ice stream up to the present day clearly requires further investigation. E-Thesis Remote sensing.;Geographic information science and geodesy. 31 12 2009 2009-12-31 COLLEGE NANME Geography COLLEGE CODE Swansea University Doctoral Ph.D 2018-08-02T16:24:29.7121972 2018-08-02T16:24:29.7121972 Faculty of Science and Engineering School of Biosciences, Geography and Physics - Geography Helena Juliet Sykes NULL 1 0042575-02082018162505.pdf 10805324.pdf 2018-08-02T16:25:05.2800000 Output 17989601 application/pdf E-Thesis true 2018-08-02T16:25:05.2800000 false
title Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
spellingShingle Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
Helena Juliet Sykes
title_short Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
title_full Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
title_fullStr Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
title_full_unstemmed Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
title_sort Rutford and Evans Ice Streams investigated using satellite radar interferometry and modelling.
author_id_str_mv ad32695f7020ebccd3f083fdc4434540
author_id_fullname_str_mv ad32695f7020ebccd3f083fdc4434540_***_Helena Juliet Sykes
author Helena Juliet Sykes
author2 Helena Juliet Sykes
format E-Thesis
publishDate 2009
institution Swansea University
college_str Faculty of Science and Engineering
hierarchytype
hierarchy_top_id facultyofscienceandengineering
hierarchy_top_title Faculty of Science and Engineering
hierarchy_parent_id facultyofscienceandengineering
hierarchy_parent_title Faculty of Science and Engineering
department_str School of Biosciences, Geography and Physics - Geography{{{_:::_}}}Faculty of Science and Engineering{{{_:::_}}}School of Biosciences, Geography and Physics - Geography
document_store_str 1
active_str 0
description The Rutford and Evans Ice Streams together drain over 150,000 km2 of the West Antarctic Ice Sheet, a marine ice sheet with much of its bed below sea level. Ice streams make up only 13% of the Antarctic coastline, but are responsible for 90% of the discharge across the grounding line, where the ice starts to float. The Rutford and Evans Ice Streams were investigated using the remote sensing method of interferometry, which uses the phase difference between successive Synthetic Aperture Radar (SAR) satellite images to derive displacement in the line-of-sight (LOS) direction of the satellite and topography, which can be separated with further processing. The grounding zones of both ice streams were mapped from clearly defined changes in vertical tidal motion visible in the interferograms. The Rutford grounding zone is dominated by a central pinning point, and the Evans grounding zone has a complex shape so that for much of the main trunk of the ice stream the east side is grounded and the west side is floating. The tidal signal for each ice stream was reconstructed, and the tidal ranges of the Rutford and Evans grounding zones are more than 6 m and 5 m respectively, both well above average for Antarctica. Vertical displacement observed in both single and double difference interferograms correlated well to changing tidal height. The width of the grounding zone modelled using an elastic beam was close to the observed grounding zone width for both ice streams. Successful differential interferometry relies on the validity of the Constant Velocity Assumption (CVA), which states that interferograms differenced to derive topographic phase must contain the same displacement phase. However, due to the large tidal ranges at the grounding lines both ice streams, this assumption, which would be better termed the Constant Displacement Assumption (CDA), was violated to an extent which may be unprecedented in the literature. The Rutford Ice Stream reached velocities of approximately 400 m a-1 at its grounding line between 1992 and 1996, and the Evans Ice Stream appears to have decreased in speed from 750 m a-1 in 1992 to 540 m a-1 in 1996. This would have a significant effect on mass balance. The behaviour of this ice stream up to the present day clearly requires further investigation.
published_date 2009-12-31T03:53:14Z
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score 11.016235

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