scholarly journals Use of ice-sheet normal modes for initialization and modelling small changes

1997 ◽  
Vol 25 ◽  
pp. 85-95 ◽  
Author(s):  
Richard C. A. Hindmarsh
Keyword(s):  
Normal Mode ◽  
Time Constant ◽  
Normal Modes ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Short Term ◽  
Scale Theory ◽  
Digital Elevation ◽  
Linearized Model ◽  
Term Response

Linearizations about two horizontal-dimensional ice sheets are proposed as methods of generating normal mode initializations for ice-sheet models and for computing the short-term response. Linearized models can be generated directly from balance-flux calculations without the need for tuning the rate factor.A linearized model is compared with the Eismint Benchmark, and the normal modes for two coarse Antarctic digital elevation models are computed and compared. Volumetric relaxation spectra are presented. The slowest mode has a time constant comparable to that computed from scale theory.

scholarly journals Use of ice-sheet normal modes for initialization and modelling small changes

1997 ◽  
Vol 25 ◽  
pp. 85-95 ◽  
Author(s):  
Richard C. A. Hindmarsh
Keyword(s):  
Normal Mode ◽  
Time Constant ◽  
Normal Modes ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Short Term ◽  
Scale Theory ◽  
Digital Elevation ◽  
Linearized Model ◽  
Term Response

Linearizations about two horizontal-dimensional ice sheets are proposed as methods of generating normal mode initializations for ice-sheet models and for computing the short-term response. Linearized models can be generated directly from balance-flux calculations without the need for tuning the rate factor.A linearized model is compared with the Eismint Benchmark, and the normal modes for two coarse Antarctic digital elevation models are computed and compared. Volumetric relaxation spectra are presented. The slowest mode has a time constant comparable to that computed from scale theory.

scholarly journals Measurement of ice-sheet topography using satellite-radar interferometry

1996 ◽  
Vol 42 (140) ◽  
pp. 10-22 ◽  
Author(s):  
Ian Joughin ◽  
Dale Winebrenner ◽  
Mark Fahnestock ◽  
Ron Kwok ◽  
William Krabill
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Surface Displacement ◽  
Horizontal Resolution ◽  
Radar Interferometry ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Digital Elevation ◽  
Satellite Radar ◽  
Ice Sheet Topography

AbstractDetailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

Modelling the short-term response of the Greenland ice-sheet to global warming

1997 ◽  
Vol 13 (10) ◽  
pp. 733-744 ◽  
Author(s):  
R. S. W. van de Wal ◽  
J. Oerlemans
Keyword(s):  
Global Warming ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Short Term ◽  
Term Response

Linking postglacial landscapes to glacier dynamics using swath radar at Thwaites Glacier, Antarctica

Geology ◽  
2020 ◽  
Vol 48 (3) ◽  
pp. 268-272 ◽  
Author(s):  
N. Holschuh ◽  
K. Christianson ◽  
J. Paden ◽  
R.B. Alley ◽  
S. Anandakrishnan
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Radar Data ◽  
West Antarctica ◽  
Erosion And Deposition ◽  
Subglacial Environment ◽  
Digital Elevation ◽  
Basal Shear ◽  
Insight Into

Abstract Ice sheets reshape Earth’s surface. Maps of the landscape formed by past ice sheets are our best tool for reconstructing historic ice sheet behavior. But models of glacier erosion and deposition that explain mapped features are relatively untested, and without observations of landforms developing in situ, postglacial landscapes can provide only qualitative insight into past ice sheet conditions. Here we present the first swath radar data collected in Antarctica, demonstrating the ability of swath radar technology to map the subglacial environment of Thwaites Glacier (West Antarctica) at comparable resolutions to digital elevation models of deglaciated terrain. Incompatibility between measured bedform orientation and predicted subglacial water pathways indicates that ice, not water, is the primary actor in initiating bedform development at Thwaites Glacier. These data show no clear relationship between morphology and glacier speed, a weak relationship between morphology and basal shear stress, and highlight a likely role for preexisting geology in glacial bedform shape.

scholarly journals Measurement of ice-sheet topography using satellite-radar interferometry

1996 ◽  
Vol 42 (140) ◽  
pp. 10-22 ◽  
Author(s):  
Ian Joughin ◽  
Dale Winebrenner ◽  
Mark Fahnestock ◽  
Ron Kwok ◽  
William Krabill
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Surface Displacement ◽  
Horizontal Resolution ◽  
Radar Interferometry ◽  
Altimeter Data ◽  
Laser Altimeter ◽  
Digital Elevation ◽  
Satellite Radar ◽  
Ice Sheet Topography

Abstract Detailed digital elevation models (DEMs) do not exist for much of the Greenland and Antartic ice sheets. Radar altimetry is at present the primary, in many cases the only, source of topographic data over the ice sheets, but the horizontal resolution of such data is coarse. Satellite-radar interferometry uses the phase difference between pairs of synthetic aperture radar (SAR) images to measure both ice-sheet topography and surface displacement. We have applied this technique using ERS-1 SAR data to make detailed (i.e. 80 m horizontal resolution) maps of surface topography in a 100 km by 300 km strip in West Greenland, extending northward from just above Jakobshavns Isbræ. Comparison with а 76 km long line of airborne laser-altimeter data shows that We have achieved a relative accuracy of 2.5 m along the profile. These observations provide a detailed view of dynamically Supported topography near the margin of an ice sheet. In the final section We compare our estimate of topography with phase contours due to motion, and confirm our earlier analysis concerning vertical ice-sheet motion and complexity in ERS-1 SAR interferograms.

A topological approach to the strain-rate pattern of ice sheets

1993 ◽  
Vol 39 (131) ◽  
pp. 10-14 ◽  
Author(s):  
J. F. Nye
Keyword(s):  
Strain Rate ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Point Of View ◽  
Principal Strain ◽  
Topological Approach ◽  
Contour Maps ◽  
Isotropic Point ◽  
Horizontal Strain

AbstractThe pattern of horizontal strain rate in an ice sheet is discussed from a topological point of view. In a circularly symmetric ice sheet, the isotropic point for strain rate at its centre is degenerate and structurally unstable. On perturbation the degenerate point splits into two elementary isotropic points, each of which has the lemon pattern for the trajectories of principal strain rate. Contour maps of principal strain-rate values are presented which show the details of the splitting.

Analysis and Simulation of Altimeter Performance for the Production of Ice Sheet Topographic Maps

1986 ◽  
Vol 8 ◽  
pp. 141-145 ◽  
Author(s):  
K.C. Partington ◽  
C.G. Rapley
Keyword(s):  
High Precision ◽  
Systems Analysis ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Data Interpretation ◽  
Topographic Maps ◽  
Error Signal ◽  
Tracking Systems ◽  
Tracking Mode ◽  
Non Linear

Satellite-borne, radar altimeters have already demonstrated an ability to produce high-precision, topographic maps of the ice sheets. Seasat operated in a tracking mode, designed for use over oceans, but successfully tracked much of the flatter regions of the ice sheet to ± 72° latitude. ERS-1 will extend coverage to ± 82° latitude and will be equipped with an ocean mode similar to that of Seasat and an ice mode designed to permit tracking of the steeper, peripheral regions. The ocean mode will be used over the flatter regions, because of its greater precision.Altimeter performance over the ice sheets has been investigated through a study of Seasat tracking behaviour and the use of an altimeter performance simulator, with a view to assessing the likely performance of ERS-1 and the design of improved tracking systems. Analysis of Seasat data shows that lock was frequently lost, as a result of possessing a non-linear height error signal over the width of the range window. Having lost lock, the tracker frequently failed to transfer rapidly and effectively to track mode. Use of the altimeter performance simulator confirms many of the findings from Seasat data and it is being used to facilitate data interpretation and mapping, through the modelling of waveform sequence.

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