scholarly journals Digital Mapping of the Nordaustlandet Ice Caps from Airborne Geophysical Investigations

1986 ◽  
Vol 8 ◽  
pp. 51-58 ◽  
Author(s):  
J.A. Dowdeswell ◽  
D.J. Drewry ◽  
A.P.R. Cooper ◽  
M.R. Gorman ◽  
O. Liestøl ◽  
...  
Keyword(s):  
Magnetic Energy ◽  
Direct Access ◽  
Ice Thickness ◽  
Ice Caps ◽  
Digital Mapping ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Geophysical Investigations ◽  
Data Source ◽  
Electro Magnetic

Airborne geophysical investigations of the previously tittle-studied Nordaustlandet ice caps (11 150 km2) took place in 1983, using SPRI 60 MHz radio echo-sounding (RES) equipment of 160 dB system performance. RES and navigational data were recorded digitally. Navigation used a ranging system (accurate to ±30 m) from aircraft to ground-based transponders, located by satellite geoceivers, supplemented by the aircraft’s navigational instruments and timed crossings of known features. Ice surface and bedrock elevations were measured, using aircraft pressure altitude, terrain clearance, and ice thickness data. The mean error of 251 crossing points on Austfonna was 11 m. The reduced geophysical data are stored on a direct-access computer database. During 3400 km of flying, Austfonna (8105 km2) was covered by traverses a nominal 5 km apart, whereas a 15 km-spaced grid was flown over Vestfonna (2510 km2). Maps of ice surface morphology and subglacial, bedrock topography were produced for Austfonna and Vestfonna, along with an ice thickness map of Austfonna, Austfonna reaches a maximum surface elevation of 791 m and ice thickness of 583 m. 28% of the bedrock area beneath Austfonna lies below sea level. RES yielded bedrock echoes for 91% of track over Austfonna, but only 52% over Vestfonna. This was probably due to warmer conditions on Vestfonna, resulting in greater absorption and scattering of electro-magnetic energy. Ice surface elevations are a principal data source in the revision of official Norwegian maps of Nordaustlandet.

scholarly journals Digital Mapping of the Nordaustlandet Ice Caps from Airborne Geophysical Investigations

1986 ◽  
Vol 8 ◽  
pp. 51-58 ◽  
Author(s):  
J.A. Dowdeswell ◽  
D.J. Drewry ◽  
A.P.R. Cooper ◽  
M.R. Gorman ◽  
O. Liestøl ◽  
...  
Keyword(s):  
Magnetic Energy ◽  
Direct Access ◽  
Ice Thickness ◽  
Ice Caps ◽  
Digital Mapping ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Geophysical Investigations ◽  
Data Source ◽  
Electro Magnetic

Airborne geophysical investigations of the previously tittle-studied Nordaustlandet ice caps (11 150 km2) took place in 1983, using SPRI 60 MHz radio echo-sounding (RES) equipment of 160 dB system performance. RES and navigational data were recorded digitally. Navigation used a ranging system (accurate to ±30 m) from aircraft to ground-based transponders, located by satellite geoceivers, supplemented by the aircraft’s navigational instruments and timed crossings of known features. Ice surface and bedrock elevations were measured, using aircraft pressure altitude, terrain clearance, and ice thickness data. The mean error of 251 crossing points on Austfonna was 11 m. The reduced geophysical data are stored on a direct-access computer database. During 3400 km of flying, Austfonna (8105 km2) was covered by traverses a nominal 5 km apart, whereas a 15 km-spaced grid was flown over Vestfonna (2510 km2). Maps of ice surface morphology and subglacial, bedrock topography were produced for Austfonna and Vestfonna, along with an ice thickness map of Austfonna, Austfonna reaches a maximum surface elevation of 791 m and ice thickness of 583 m. 28% of the bedrock area beneath Austfonna lies below sea level. RES yielded bedrock echoes for 91% of track over Austfonna, but only 52% over Vestfonna. This was probably due to warmer conditions on Vestfonna, resulting in greater absorption and scattering of electro-magnetic energy. Ice surface elevations are a principal data source in the revision of official Norwegian maps of Nordaustlandet.

Surface and Bedrock Topography of Ice Caps in Iceland, Mapped by Radio Echo-Sounding

1986 ◽  
Vol 8 ◽  
pp. 11-18 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Surface Elevation ◽  
Ice Thickness ◽  
Volcanic Complex ◽  
Glacier Surface ◽  
Ice Caps ◽  
Ice Cap ◽  
North East ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Echo Sounding

Since 1977, large areas on western Vatnajökull have been surveyed by ground-based, radio echo-sounding and the whole ice cap, HofsjökuIl, was surveyed in 1983. Detailed maps of the glacier-surface elevation and the sub-ice bedrock have been compiled. The instrumentation includes a 2–5 MHz, mono-pulse echo-sounder, for continuous profiling, a satellite geoceiver and Loran-C equipment, for navigation, and a precision pressure altimeter. The maps of western Vatnajökull cover about 1500 km2 and are compiled from 1500 km-long sounding lines, which yielded about 50 000 data points for ice thickness and 20 000 points for ice-surface elevation. The maps of HofsjökuIl cover 923 km2, the sounding lines were 1350 km long; 42 000 points were used for determining ice thickness and 30 000 for surface elevation. The maps obtained from these data are the first ones of the ice caps with surface elevation of known accuracy. The bedrock map of western Vatnajökull shows details of volcanic ridges and subglacial valleys, running north-east to south-west, as well as the central, volcanic complexes, Hamarinn, Bárdarbunga, and Grimsvtön and the related fissure swarms. The map of Hofsjökull reveals a large volcanic complex, with a 650 m deep caldera. The landforms in southern Hofsjökull are predominantly aligned from north to south, but those in the northern ice cap run north by 25° east.

scholarly journals Surface and Bedrock Topography of Ice Caps in Iceland, Mapped by Radio Echo-Sounding

1986 ◽  
Vol 8 ◽  
pp. 11-18 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Surface Elevation ◽  
Ice Thickness ◽  
Volcanic Complex ◽  
Glacier Surface ◽  
Ice Caps ◽  
Ice Cap ◽  
North East ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Echo Sounding

Since 1977, large areas on western Vatnajökull have been surveyed by ground-based, radio echo-sounding and the whole ice cap, HofsjökuIl, was surveyed in 1983. Detailed maps of the glacier-surface elevation and the sub-ice bedrock have been compiled. The instrumentation includes a 2–5 MHz, mono-pulse echo-sounder, for continuous profiling, a satellite geoceiver and Loran-C equipment, for navigation, and a precision pressure altimeter. The maps of western Vatnajökull cover about 1500 km2 and are compiled from 1500 km-long sounding lines, which yielded about 50 000 data points for ice thickness and 20 000 points for ice-surface elevation. The maps of HofsjökuIl cover 923 km2, the sounding lines were 1350 km long; 42 000 points were used for determining ice thickness and 30 000 for surface elevation. The maps obtained from these data are the first ones of the ice caps with surface elevation of known accuracy. The bedrock map of western Vatnajökull shows details of volcanic ridges and subglacial valleys, running north-east to south-west, as well as the central, volcanic complexes, Hamarinn, Bárdarbunga, and Grimsvtön and the related fissure swarms. The map of Hofsjökull reveals a large volcanic complex, with a 650 m deep caldera. The landforms in southern Hofsjökull are predominantly aligned from north to south, but those in the northern ice cap run north by 25° east.

Airborne UHF Radio Echo-Sounding of Three Yukon Glaciers

1980 ◽  
Vol 25 (91) ◽  
pp. 23-32 ◽  
Author(s):  
B. B Narod ◽  
G. K. C. Clarke
Keyword(s):  
Field Trials ◽  
High Gain ◽  
Yukon Territory ◽  
Ice Thickness ◽  
Spatial Averaging ◽  
Ice Caps ◽  
Signal Degradation ◽  
High Gain Antenna ◽  
Radio Echo Sounding ◽  
Moving Platform

AbstractA high-resolution radio echo-sounder operating at a frequency of 840 MHz has been developed for airborne sounding of small and medium-sized polar glaciers and ice caps. The sounder uses a compact,, high-gain antenna which suppresses valley-wall echoes and simplifies operation from light aircraft, Successful field trials were carried out on Rusty, Trapridge, and Hazard Glaciers, Yukon Territory, Canada. Results compare well with ice depths obtained from earlier ground-based soundings on Rusty and Trapridge Glaciers. The maximum ice thickness encountered was 200 m on Hazard Glacier.Owing to the high operating frequency, random scattering from inhomogeneities within the ice is a major cause of signal degradation. For this reason the sounder cannot penetrate great thicknesses of temperate or debris-rich ice. Spatial averaging, an immediate result of operating from a moving platform, reduces the effects of back-scattered “clutter”.

scholarly journals Drainage-Basin Characteristics of Nordaustlandet Ice Caps, Svalbard

1986 ◽  
Vol 32 (110) ◽  
pp. 31-38 ◽  
Author(s):  
Julian A. Dowdeswell
Keyword(s):  
Drainage Basin ◽  
High Surface ◽  
Shear Zones ◽  
Drainage Basins ◽  
Ice Streams ◽  
Ice Caps ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Surface Profiles ◽  
Basal Melting

AbstractRecent mapping of ice-surface and bedrock topography from airborne radio-echo sounding has shown that the ice caps of Nordaustlandet, Svalbard, are divided into a series of well-defined drainage basins. Three lines of evidence indicate that several distinctive modes of ice-flow regime characterize these basins: (1) comparison between observed and theoretical ice-surface profiles; (2) analysis of driving stresses; and (3) observations of ice-surface features on satellite imagery and air photographs. The drainage basins are inferred to behave in the following ways. First, basins with low driving stresses and surface profiles, some of them clearly stagnant, are associated with the quiescent phase between glacier surges. Secondly, the ice streams draining southern Vestfonna have low surface profiles, relatively low driving stresses, and marked shear zones at their margins. They are interpreted to be flowing continuously at a relatively faster rate than the ridges between them. Basal melting, perhaps combined with substrate deformation, is probably responsible for the regime of these glaciers. Thirdly, the remaining basins studied on Nordaustlandet have relatively high marginal driving stresses and high surface profiles. They are interpreted to be frozen to their beds, at least near their margins. Some of these basins may also surge, particularly those where a part of the basin is below sea-level, and therefore is probably underlain by considerable thicknesses of deformable sediments.

scholarly journals Surface elevation, ice thickness, and subglacial-bedrock topography of Ekström Ice Shelf (Antarctica) and its catchment area

2000 ◽  
Vol 30 ◽  
pp. 61-68 ◽  
Author(s):  
H. Sandhäger ◽  
N. Blindow
Keyword(s):  
Catchment Area ◽  
Drainage System ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Bedrock Topography ◽  
Ice Surface ◽  
Catchment Areas ◽  
Grounding Line ◽  
Radio Echo Sounding ◽  
Mass Discharge

AbstractEkström Ice Shelf and its catchment area form a comparatively small (∼29 000 km2) drainage system in northern Dronning Maud Land, Antarctica. Aerial-altimetry and radio-echo-sounding data of this region have been used to derive detailed maps of ice-surface and bedrock topographies and ice thickness. With the new database the volumes of the floating and grounded ice in the drainage system are calculated to be ∼3200 km3 and ∼16 000 km3, respectively. This corresponds to a total ice mass of ∼17 000 Gt. Four significant graben-like depressions in the bedrock topography have been identified, which incline from inland towards the grounding line and are up to ∼16 km wide there. These structures coincide with the particular zones of concentrated ice flux into the ice shelf. The total mean annual mass discharge over the grounding line of the larger western part and the smaller eastern part of Ekström Ice Shelf is estimated to be about 3.7 Gt and 0.4 Gt, respectively. Both parts represent individual ice-shelf systems with different catchment areas, geometric characteristics and flow regimes.

Drainage-Basin Characteristics of Nordaustlandet Ice Caps, Svalbard

1986 ◽  
Vol 32 (110) ◽  
pp. 31-38 ◽  
Author(s):  
Julian A. Dowdeswell
Keyword(s):  
Drainage Basin ◽  
High Surface ◽  
Shear Zones ◽  
Drainage Basins ◽  
Ice Streams ◽  
Ice Caps ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Surface Profiles ◽  
Basal Melting

AbstractRecent mapping of ice-surface and bedrock topography from airborne radio-echo sounding has shown that the ice caps of Nordaustlandet, Svalbard, are divided into a series of well-defined drainage basins. Three lines of evidence indicate that several distinctive modes of ice-flow regime characterize these basins: (1) comparison between observed and theoretical ice-surface profiles; (2) analysis of driving stresses; and (3) observations of ice-surface features on satellite imagery and air photographs. The drainage basins are inferred to behave in the following ways. First, basins with low driving stresses and surface profiles, some of them clearly stagnant, are associated with the quiescent phase between glacier surges. Secondly, the ice streams draining southern Vestfonna have low surface profiles, relatively low driving stresses, and marked shear zones at their margins. They are interpreted to be flowing continuously at a relatively faster rate than the ridges between them. Basal melting, perhaps combined with substrate deformation, is probably responsible for the regime of these glaciers. Thirdly, the remaining basins studied on Nordaustlandet have relatively high marginal driving stresses and high surface profiles. They are interpreted to be frozen to their beds, at least near their margins. Some of these basins may also surge, particularly those where a part of the basin is below sea-level, and therefore is probably underlain by considerable thicknesses of deformable sediments.

Forms of Glacial Relief of Spitsbergen Glaciers

1981 ◽  
Vol 2 ◽  
pp. 45-51 ◽  
Author(s):  
Yu. Ya. Macheret
Keyword(s):  
Correlation Analysis ◽  
Outer Region ◽  
Ice Thickness ◽  
Multiple Correlation ◽  
Ice Caps ◽  
Mountain Glaciers ◽  
Significant Relationships ◽  
Radio Echo Sounding ◽  
Multiple Correlation Analysis ◽  
Echo Sounding

Results are given of radio echo‐sounding of 53 glaciers of different sizes and glaciological regimes during 1974–75 and 1977–79 in Spitsbergen. Mountain glaciers have maximum ice thicknesses ranging from 90 to 350 m. Thicknesses up to 165 m, as well as the presence of overdeepened sections of the bed and subglacial ridges up to 100 m high are typical. Other glaciers have ice thickness values of up to 500 m (e.g. Veteranen) but on some sections of glaciers and ice caps depressions in the bed with ice thicknesses reaching 540 m have been found, which exceed the “background” thickness by 200 to 400 m. Subglacial relief of Vestfonna, Nordaustlandet, is very rough in its outer region but is rather smooth in the central part beneath the ice dome, where ice thickness reaches 385 m. Multiple correlation analysis of 15 glaciers indicates a number of significant relationships between the area of terminal and lateral moraines of glaciers and length, area, and, consequently, volume.

scholarly journals Bed topography of Princess Elizabeth Land in East Antarctica

2020 ◽  
Author(s):  
Xiangbin Cui ◽  
Hafeez Jeofry ◽  
Jamin S. Greenbaum ◽  
Jingxue Guo ◽  
Lin Li ◽  
...  
Keyword(s):  
Gravity Data ◽  
Mass Conservation ◽  
East Antarctica ◽  
Ice Thickness ◽  
Surface Model ◽  
Hydraulic Pressure ◽  
Satellite Gravity ◽  
Free Zone ◽  
Ice Surface ◽  
Radio Echo Sounding

Abstract. We present a topographic digital elevation model (DEM) for Princess Elizabeth Land (PEL), East Antarctica – the last remaining region in Antarctica to be surveyed by airborne radio-echo sounding (RES) techniques. The DEM covers an area of ~900,000 km2 and was established from new RES data collected by the ICECAP-2 consortium, led by the Polar Research Institute of China, from four campaigns since 2015. Previously, the region (along with Recovery basin elsewhere in East Antarctica) was characterised by an inversion using low resolution satellite gravity data across a large (>200 km wide) data-free zone to generate the Bedmap2 topographic product. We use the mass conservation (MC) method to produce an ice thickness grid across faster-flowing (>30 m yr-1) regions of the ice sheet and streamline diffusion in slower-flowing areas. The resulting ice thickness model is integrated with an ice surface model to build the bed DEM. With the revised bed DEM, we are able to model the flow of subglacial water and assess where the hydraulic pressure, and hydrological routing, is most sensitive to small ice-surface gradient changes. Together with BedMachine Antarctica, and Bedmap2, this new PEL bed DEM completes the first order measurement of subglacial continental Antarctica – an international mission that began around 70 years ago. The ice thickness and bed elevation DEMs of PEL (resolved horizontally at 500 m relative to ice surface elevations obtained from a combination of European Remote Sensing Satellite 1 radar (ERS-1) and Ice, Cloud and Land Elevation Satellite (ICESat) laser satellite altimetry datasets) are accessible from https://doi.org/10.5281/zenodo.3666088 (Cui et 38al., 2020).

scholarly journals Airborne UHF Radio Echo-Sounding of Three Yukon Glaciers

1980 ◽  
Vol 25 (91) ◽  
pp. 23-32
Author(s):  
B. B Narod ◽  
G. K. C. Clarke
Keyword(s):  
Field Trials ◽  
High Gain ◽  
Yukon Territory ◽  
Ice Thickness ◽  
Spatial Averaging ◽  
Ice Caps ◽  
Signal Degradation ◽  
High Gain Antenna ◽  
Radio Echo Sounding ◽  
Moving Platform

AbstractA high-resolution radio echo-sounder operating at a frequency of 840 MHz has been developed for airborne sounding of small and medium-sized polar glaciers and ice caps. The sounder uses a compact,, high-gain antenna which suppresses valley-wall echoes and simplifies operation from light aircraft, Successful field trials were carried out on Rusty, Trapridge, and Hazard Glaciers, Yukon Territory, Canada. Results compare well with ice depths obtained from earlier ground-based soundings on Rusty and Trapridge Glaciers. The maximum ice thickness encountered was 200 m on Hazard Glacier.Owing to the high operating frequency, random scattering from inhomogeneities within the ice is a major cause of signal degradation. For this reason the sounder cannot penetrate great thicknesses of temperate or debris-rich ice. Spatial averaging, an immediate result of operating from a moving platform, reduces the effects of back-scattered “clutter”.

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