Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica
The influence of basal disturbances on the steady-state surface topography and on surface velocities of glaciers and ice sheets is investigated numerically. This is done for finite-amplitude basal perturbations in both bed topography and basal slipperiness using a non-linear ice rheology and a non-l...
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ETH Zürich
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ftunivnorthumb:oai:nrl.northumbria.ac.uk:36256 2023-05-15T13:56:54+02:00 Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica Raymond, Mélanie Gudmundsson, Hilmar 2007-09-01 https://nrl.northumbria.ac.uk/id/eprint/36256/ https://www.ethz.ch/content/dam/ethz/special-interest/baug/vaw/vaw-dam/documents/das-institut/mitteilungen/2000-2009/202.pdf unknown ETH Zürich Raymond, Mélanie and Gudmundsson, Hilmar (2007) Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica. Mitteilungen der Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie an der Eidgenossischen Technischen Hochschule Zurich, 202. pp. 107-139. ISSN 0374-0056 F800 Physical and Terrestrial Geographical and Environmental Sciences Article PeerReviewed 2007 ftunivnorthumb 2022-09-25T06:08:17Z The influence of basal disturbances on the steady-state surface topography and on surface velocities of glaciers and ice sheets is investigated numerically. This is done for finite-amplitude basal perturbations in both bed topography and basal slipperiness using a non-linear ice rheology and a non-linear sliding law. The effects of varying the exponent n in Glen's flow law on transfer characteristics are mainly quantitative, and do not affect qualitative aspects of the transfer amplitudes and phase shifts such as the number of maxima and inflection points when plotted as functions of wavelength. In particular, the well-known maximum in bed-to-surface transfer amplitude for a Newtonian medium at sufficiently high slip ratios (ratio between mean sliding velocity and mean ice deformational velocity) also forms for n > 1. Transfer amplitudes generally become smaller with increasing n for wavelengths less than about three times the mean ice thickness (h). For larger wavelengths the situation is reversed and transfer amplitudes increase with n. For active ice streams, characterized by high basal slipperiness, low surface slopes (< 0.5°), and n = 3, topographic transfer amplitudes are generally large (> 0.5) and fairly constant for all wavelengths longer than about 3 to 5 h. With increasing n and decreasing surface slope the lower limit of wavelengths over which horizontal stress gradients can be ignored increases markedly. Perturbation solutions for Newtonian medium are found to give an accurate description of the transfer characteristics for bedrock amplitudes up to 50 % ice thickness and for fractional amplitudes of slipperiness perturbations up to 0.5. Article in Journal/Newspaper Antarc* Antarctica Rutford Ice Stream West Antarctica Northumbria University, Newcastle: Northumbria Research Link (NRL) Rutford ENVELOPE(-85.300,-85.300,-78.600,-78.600) Rutford Ice Stream ENVELOPE(-80.000,-80.000,-79.167,-79.167) West Antarctica |
institution |
Open Polar |
collection |
Northumbria University, Newcastle: Northumbria Research Link (NRL) |
op_collection_id |
ftunivnorthumb |
language |
unknown |
topic |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
spellingShingle |
F800 Physical and Terrestrial Geographical and Environmental Sciences Raymond, Mélanie Gudmundsson, Hilmar Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
topic_facet |
F800 Physical and Terrestrial Geographical and Environmental Sciences |
description |
The influence of basal disturbances on the steady-state surface topography and on surface velocities of glaciers and ice sheets is investigated numerically. This is done for finite-amplitude basal perturbations in both bed topography and basal slipperiness using a non-linear ice rheology and a non-linear sliding law. The effects of varying the exponent n in Glen's flow law on transfer characteristics are mainly quantitative, and do not affect qualitative aspects of the transfer amplitudes and phase shifts such as the number of maxima and inflection points when plotted as functions of wavelength. In particular, the well-known maximum in bed-to-surface transfer amplitude for a Newtonian medium at sufficiently high slip ratios (ratio between mean sliding velocity and mean ice deformational velocity) also forms for n > 1. Transfer amplitudes generally become smaller with increasing n for wavelengths less than about three times the mean ice thickness (h). For larger wavelengths the situation is reversed and transfer amplitudes increase with n. For active ice streams, characterized by high basal slipperiness, low surface slopes (< 0.5°), and n = 3, topographic transfer amplitudes are generally large (> 0.5) and fairly constant for all wavelengths longer than about 3 to 5 h. With increasing n and decreasing surface slope the lower limit of wavelengths over which horizontal stress gradients can be ignored increases markedly. Perturbation solutions for Newtonian medium are found to give an accurate description of the transfer characteristics for bedrock amplitudes up to 50 % ice thickness and for fractional amplitudes of slipperiness perturbations up to 0.5. |
format |
Article in Journal/Newspaper |
author |
Raymond, Mélanie Gudmundsson, Hilmar |
author_facet |
Raymond, Mélanie Gudmundsson, Hilmar |
author_sort |
Raymond, Mélanie |
title |
Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
title_short |
Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
title_full |
Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
title_fullStr |
Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
title_full_unstemmed |
Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica |
title_sort |
estimating glacier basal properties from surface measurements: a non-linear inversion approach applied to the rutford ice stream, west antarctica |
publisher |
ETH Zürich |
publishDate |
2007 |
url |
https://nrl.northumbria.ac.uk/id/eprint/36256/ https://www.ethz.ch/content/dam/ethz/special-interest/baug/vaw/vaw-dam/documents/das-institut/mitteilungen/2000-2009/202.pdf |
long_lat |
ENVELOPE(-85.300,-85.300,-78.600,-78.600) ENVELOPE(-80.000,-80.000,-79.167,-79.167) |
geographic |
Rutford Rutford Ice Stream West Antarctica |
geographic_facet |
Rutford Rutford Ice Stream West Antarctica |
genre |
Antarc* Antarctica Rutford Ice Stream West Antarctica |
genre_facet |
Antarc* Antarctica Rutford Ice Stream West Antarctica |
op_relation |
Raymond, Mélanie and Gudmundsson, Hilmar (2007) Estimating glacier basal properties from surface measurements: A non-linear inversion approach applied to the Rutford Ice Stream, West Antarctica. Mitteilungen der Versuchsanstalt fur Wasserbau, Hydrologie und Glaziologie an der Eidgenossischen Technischen Hochschule Zurich, 202. pp. 107-139. ISSN 0374-0056 |
_version_ |
1766264499966312448 |