scholarly journals The Surface Topography of Large Ice Masses from Landsat Imagery

1987 ◽  
Vol 33 (113) ◽  
pp. 16-23 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
Neil F. McIntyre
Keyword(s):  
Surface Topography ◽  
Landsat Imagery ◽  
Ice Sheet ◽  
Surface Characteristics ◽  
Drainage Basins ◽  
Landsat Images ◽  
Antarctic Ice Sheet ◽  
Ice Caps ◽  
Ice Surface ◽  
The Antarctic

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of <10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

scholarly journals The Surface Topography of Large Ice Masses from Landsat Imagery

1987 ◽  
Vol 33 (113) ◽  
pp. 16-23 ◽  
Author(s):  
Julian A. Dowdeswell ◽  
Neil F. McIntyre
Keyword(s):  
Surface Topography ◽  
Landsat Imagery ◽  
Ice Sheet ◽  
Surface Characteristics ◽  
Drainage Basins ◽  
Landsat Images ◽  
Antarctic Ice Sheet ◽  
Ice Caps ◽  
Ice Surface ◽  
The Antarctic

AbstractApparent ice-surface topography is observed at several scales on Landsat multi-spectral scanner (MSS) imagery. Digitally enhanced MSS scenes from Antarctica and Nordaustlandet, Svalbard, are compared with ice-surface elevations from aircraft altimetry (relative accuracy 2–3 m) to show that this apparent topography is real. Apparent ice divides on Landsat images fit closely with divides on altimetric records. Ice-surface irregularities within drainage basins are also shown to be real. On Byrd Glacier, Antarctica, apparent “flow lines” coincide with ridges on altimetric records. Synoptic Landsat data, calibrated by information from aircraft altimetric flight lines, are used to classify the surface roughness of the ice caps on Nordaustlandet and 40% of the Antarctic ice sheet. On Nordaustlandet, the roughest ice is of amplitude 15–25 m and wavelength 3–4.5 km. Drainage basins with such rough surface characteristics may be associated with ice streams or possibly past surge activity. The most rough Antarctic terrain is up to 60 m in amplitude, with wavelengths of &lt;10 km. The roughness of the Antarctic ice sheet increases with distance from ice divides, reflecting changes in the parameters affecting the transfer of basal stresses to the ice surface.

scholarly journals Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?

2014 ◽  
Vol 2 (2) ◽  
pp. 911-933 ◽  
Author(s):  
N. F. Glasser ◽  
S. J. A. Jennings ◽  
M. J. Hambrey ◽  
B. Hubbard
Keyword(s):  
Flow Line ◽  
Ice Sheet ◽  
Surface Structures ◽  
Surface Velocity ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Ice Surface ◽  
Ice Stream ◽  
The Antarctic

Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

scholarly journals Comparison of Surface Characteristics of the Antarctic Ice Sheet with Satellite Observations (Abstract)

1987 ◽  
Vol 9 ◽  
pp. 253
Author(s):  
N. Young ◽  
I. Goodwin
Keyword(s):  
Surface Topography ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Ground Truth ◽  
Surface Characteristics ◽  
Small Scale ◽  
Landsat Images ◽  
Ground Truth Data ◽  
Additional Information ◽  
Wilkes Land

Ground surveys of the ice sheet in Wilkes Land, Antarctica, have been made on oversnow traverses operating out of Casey. Data collected include surface elevation, accumulation rate, snow temperature, and physical characteristics of the snow cover. By the nature of the surveys, the data are mostly restricted to line profiles. In some regions, aerial surveys of surface topography have been made over a grid network. Satellite imagery and remote sensing are two means of extrapolating the results from measurements along lines to an areal presentation. They are also the only source of data over large areas of the continent. Landsat images in the visible and near infra-red wavelengths clearly depict many of the large- and small scale features of the surface. The intensity of the reflected radiation varies with the aspect and magnitude of the surface slope to reveal the surface topography. The multi-channel nature of the Landsat data is exploited to distinguish between different surface types through their different spectral signatures, e.g. bare ice, glaze, snow, etc. Additional information on surface type can be gained at a coarser scale from other satellite-borne sensors such as ESMR, SMMR, etc. Textural enhancement of the Landsat images reveals the surface micro-relief. Features in the enhanced images are compared to ground-truth data from the traverse surveys to produce a classification of surface types across the images and to determine the magnitude of the surface topography and micro-relief observed. The images can then be used to monitor changes over time.

scholarly journals A comparison between active and passive microwave measurements of the Antarctic ice sheet and their association with the surface katabatic winds

1991 ◽  
Vol 37 (125) ◽  
pp. 3-10 ◽  
Author(s):  
F. Remy ◽  
J. F. Minster
Keyword(s):  
Strong Correlation ◽  
Ice Sheet ◽  
Microwave Signal ◽  
Passive Microwave ◽  
Microwave Measurements ◽  
Strongly Correlated ◽  
Katabatic Winds ◽  
Antarctic Ice Sheet ◽  
Ice Surface ◽  
The Antarctic

AbstractThe intensity of the Seasat altimeter return power over Antarctica varies in strong correlation with the intensity of model katabatic winds. It is also strongly correlated with the polarization of the passive microwave signal at 37 GHz of the Nimbus-7 SMMR data. It is shown that this is most likely the result of the wind-induced micro-roughness of the ice surface.

scholarly journals An improved Antarctic dataset for high resolution numerical ice sheet models (ALBMAP v1)

2010 ◽  
Vol 3 (1) ◽  
pp. 195-230 ◽  
Author(s):  
A. M. Le Brocq ◽  
A. J. Payne ◽  
A. Vieli
Keyword(s):  
High Resolution ◽  
Ice Sheet ◽  
Surface Air Temperature ◽  
Ice Thickness ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
Continental Scale ◽  
Ice Surface ◽  
The Antarctic ◽  
Ice Sheet Modelling

Abstract. The dataset described in this paper (ALBMAP) has been created for the purposes of high-resolution numerical ice sheet modelling of the Antarctic Ice Sheet. It brings together data on the ice sheet configuration (e.g. ice surface and ice thickness) and boundary conditions, such as the surface air temperature, accumulation and geothermal heat flux. The ice thickness and basal topography is based on the BEDMAP dataset (Lythe et al., 2001), however, there are a number of inconsistencies within BEDMAP and, since its release, more data has become available. The dataset described here addresses these inconsistencies, including some novel interpolation schemes for sub ice-shelf cavities, and incorporates some major new datasets. The inclusion of new datasets is not exhaustive, this considerable task is left for the next release of BEDMAP, however, the data and procedure documented here provides another step forward and demonstrates the issues that need addressing in a continental scale dataset useful for high resolution ice sheet modelling. The dataset provides an initial condition that is as close as possible to present-day ice sheet configuration, aiding modelling of the response of the Antarctic Ice Sheet to various forcings, which are, at present, not fully understood.

scholarly journals Getting around Antarctica: new high-resolution mappings of the grounded and freely-floating boundaries of the Antarctic ice sheet created for the International Polar Year

2011 ◽  
Vol 5 (3) ◽  
pp. 569-588 ◽  
Author(s):  
R. Bindschadler ◽  
H. Choi ◽  
A. Wichlacz ◽  
R. Bingham ◽  
J. Bohlander ◽  
...  
Keyword(s):  
Landsat Imagery ◽  
Ice Sheet ◽  
Beam Theory ◽  
Surface Shape ◽  
International Polar Year ◽  
Antarctic Ice Sheet ◽  
Ice Shelves ◽  
Order Of Magnitude ◽  
International Polar ◽  
The Antarctic

Abstract. Two ice-dynamic transitions of the Antarctic ice sheet – the boundary of grounded ice features and the freely-floating boundary – are mapped at 15-m resolution by participants of the International Polar Year project ASAID using customized software combining Landsat-7 imagery and ICESat/GLAS laser altimetry. The grounded ice boundary is 53 610 km long; 74 % abuts to floating ice shelves or outlet glaciers, 19 % is adjacent to open or sea-ice covered ocean, and 7 % of the boundary ice terminates on land. The freely-floating boundary, called here the hydrostatic line, is the most landward position on ice shelves that expresses the full amplitude of oscillating ocean tides. It extends 27 521 km and is discontinuous. Positional (one-sigma) accuracies of the grounded ice boundary vary an order of magnitude ranging from ±52 m for the land and open-ocean terminating segments to ±502 m for the outlet glaciers. The hydrostatic line is less well positioned with errors over 2 km. Elevations along each line are selected from 6 candidate digital elevation models based on their agreement with ICESat elevation values and surface shape inferred from the Landsat imagery. Elevations along the hydrostatic line are converted to ice thicknesses by applying a firn-correction factor and a flotation criterion. BEDMAP-compiled data and other airborne data are compared to the ASAID elevations and ice thicknesses to arrive at quantitative (one-sigma) uncertainties of surface elevations of ±3.6, ±9.6, ±11.4, ±30 and ±100 m for five ASAID-assigned confidence levels. Over one-half of the surface elevations along the grounded ice boundary and over one-third of the hydrostatic line elevations are ranked in the highest two confidence categories. A comparison between ASAID-calculated ice shelf thicknesses and BEDMAP-compiled data indicate a thin-ice bias of 41.2 &amp;pm; 71.3 m for the ASAID ice thicknesses. The relationship between the seaward offset of the hydrostatic line from the grounded ice boundary only weakly matches a prediction based on beam theory. The mapped products along with the customized software to generate them and a variety of intermediate products are available from the National Snow and Ice Data Center.

scholarly journals Origin and dynamic significance of longitudinal structures ("flow stripes") in the Antarctic Ice Sheet

2015 ◽  
Vol 3 (2) ◽  
pp. 239-249 ◽  
Author(s):  
N. F. Glasser ◽  
S. J. A. Jennings ◽  
M. J. Hambrey ◽  
B. Hubbard
Keyword(s):  
Large Scale ◽  
Ice Sheet ◽  
Surface Structures ◽  
Dimensional Structure ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Flow Perturbation ◽  
Ice Surface ◽  
Ice Stream ◽  
The Antarctic

Abstract. Longitudinal ice-surface structures in the Antarctic Ice Sheet can be traced continuously down-ice for distances of up to 1200 km. A map of the distribution of ~ 3600 of these features, compiled from satellite images, shows that they mirror the location of fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of metres per annum and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. They can be traced continuously through crevasse fields and through blue-ice areas, indicating that they represent the surface manifestation of a three-dimensional structure, interpreted as foliation. Flow lines are linear and undeformed for all major flow units described here in the Antarctic Ice Sheet except for the Kamb Ice Stream and the Institute and Möller Ice Stream areas, where areas of flow perturbation are evident. Parcels of ice along individual flow paths on the Lambert Glacier, Recovery Glacier, Byrd Glacier and Pine Island Glacier may reside in the glacier system for ~ 2500 to 18 500 years. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow configuration of the ice sheet may have remained largely unchanged for the last few hundred years, and possibly even longer. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

scholarly journals Boundary conditions of an active West Antarctic subglacial lake: implications for storage of water beneath the ice sheet

2013 ◽  
Vol 7 (3) ◽  
pp. 2979-2999 ◽  
Author(s):  
M. J. Siegert ◽  
N. Ross ◽  
H. Corr ◽  
B. Smith ◽  
T. Jordan ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Surface Elevation ◽  
Altimeter Data ◽  
Radar Altimeter ◽  
Local Flow ◽  
Antarctic Ice Sheet ◽  
Subglacial Lake ◽  
West Antarctic ◽  
Ice Surface ◽  
The Antarctic

Abstract. Repeat-pass IceSat altimetry has revealed 124 discrete surface height changes across the Antarctic Ice Sheet, interpreted to be caused by subglacial lake discharges (surface lowering) and inputs (surface uplift). Few of these active lakes have been confirmed by radio-echo sounding (RES) despite several attempts (notable exceptions are Lake Whillans and three in the Adventure Subglacial Trench). Here we present targeted RES and radar altimeter data from an "active lake" location within the upstream Institute Ice Stream, into which 0.12 km3 of water is calculated to have flowed between October 2003 and February 2008. We use a series of transects to establish an accurate appreciation of the influences of bed topography and ice-surface elevation on water storage potential. The location of surface height change is over the downslope flank of a distinct topographic hollow, where RES reveals no obvious evidence for deep (> 10 m) water. The regional hydropotential reveals a sink coincident with the surface change, however. Governed by the location of the hydrological sink, basal water will likely "drape" over existing topography in a manner dissimilar to subglacial lakes where flat strong specular RES reflections are measured. The inability of RES to detect the active lake means that more of the Antarctic ice sheet bed may contain stored water than is currently appreciated. Variation in ice surface elevation datasets leads to significant alteration in calculations of the local flow of basal water indicating the value of, and need for, high resolution RES datasets in both space and time to establish and characterise subglacial hydrological processes.

scholarly journals Comparison of Surface Characteristics of the Antarctic Ice Sheet with Satellite Observations (Abstract)

1987 ◽  
Vol 9 ◽  
pp. 253-253
Author(s):  
N. Young ◽  
I. Goodwin
Keyword(s):  
Surface Topography ◽  
Accumulation Rate ◽  
Ice Sheet ◽  
Ground Truth ◽  
Surface Characteristics ◽  
Small Scale ◽  
Landsat Images ◽  
Ground Truth Data ◽  
Additional Information ◽  
Wilkes Land

Ground surveys of the ice sheet in Wilkes Land, Antarctica, have been made on oversnow traverses operating out of Casey. Data collected include surface elevation, accumulation rate, snow temperature, and physical characteristics of the snow cover. By the nature of the surveys, the data are mostly restricted to line profiles. In some regions, aerial surveys of surface topography have been made over a grid network.Satellite imagery and remote sensing are two means of extrapolating the results from measurements along lines to an areal presentation. They are also the only source of data over large areas of the continent. Landsat images in the visible and near infra-red wavelengths clearly depict many of the large- and small scale features of the surface. The intensity of the reflected radiation varies with the aspect and magnitude of the surface slope to reveal the surface topography. The multi-channel nature of the Landsat data is exploited to distinguish between different surface types through their different spectral signatures, e.g. bare ice, glaze, snow, etc. Additional information on surface type can be gained at a coarser scale from other satellite-borne sensors such as ESMR, SMMR, etc. Textural enhancement of the Landsat images reveals the surface micro-relief.Features in the enhanced images are compared to ground-truth data from the traverse surveys to produce a classification of surface types across the images and to determine the magnitude of the surface topography and micro-relief observed. The images can then be used to monitor changes over time.

Surface Topography of the Antarctic Ice Sheet

Nature ◽  
1959 ◽  
Vol 184 (4689) ◽  
pp. 786-787 ◽  
Author(s):  
J. F. NYE
Keyword(s):  
Surface Topography ◽  
Ice Sheet ◽  
Antarctic Ice Sheet ◽  
The Antarctic
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