scholarly journals Airborne radar survey above Vostok region, east-central Antarctica: ice thickness and Lake Vostok geometry

2002 ◽  
Vol 48 (160) ◽  
pp. 62-69 ◽  
Author(s):  
Ignazio E. Tabacco ◽  
Cesido Bianchi ◽  
Achille Zirizzotti ◽  
Enrico Zuccheretti ◽  
Alessandro Forieri ◽  
...  
Keyword(s):  
Major Axis ◽  
Radar Data ◽  
Surface Elevation ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Maximum Width ◽  
East Central ◽  
Absolute Value ◽  
Lake Vostok ◽  
Ice Surface

AbstractDuring the 1999–2000 Italian Expedition, an airborne radar survey was performed along 12 transects across Lake Vostok, Antarctica, and its western and eastern margins. Ice thickness, subglacial elevation and the precise location of lake boundaries were determined. Radar data confirm the geometry derived from previous surveys, but with some slight differences. We measured a length of up to 260 km, a maximum width of 81 km and an area of roughly 14 000 km2. Along the major axis, from north to south, the ice thickness varies from 3800 to 4250 m, with a decreasing gradient. From west to east the ice thickness is fairly constant, except for two narrow strips located on the western and eastern margins, where it increases with high thickening rate. Over the lake the surface elevation increases from 3476 m a.s.l. (south) to 3525 (north), with a decreasing gradient, while the lake surface elevation decreases from −315 to −750 m a.s.l., with a decreasing gradient (absolute value). The ice-surface and lake-ceiling slopes suggest that the lake is in a state of hydrostatic equilibrium.

scholarly journals Investigations of an “ice plain” in the mouth of Pine Island Glacier, Antarctica

2001 ◽  
Vol 47 (156) ◽  
pp. 51-57 ◽  
Author(s):  
H. F. J. Corr ◽  
C. S. M. Doake ◽  
A. Jenkins ◽  
D. G. Vaughan
Keyword(s):  
Radar Data ◽  
Surface Elevation ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Centre Line ◽  
Ice Stream ◽  
Grounding Line

AbstractWe present newly acquired airborne radar data showing ice thickness and surface elevation for Pine Island Glacier, Antarctica. These data, when combined with earlier measurements, suggest the presence of a lightly grounded area immediately above the grounding line of Pine Island Glacier. We identify this region as an “ice plain”. It lies close to the centre line of the glacier, has an elevation above buoyancy of <50 m and extends inland for >28 km. The upstream edge of the ice plain is defined by a “coupling line”. The configuration of the ice plain implies that nearby thinning of the ice stream would result in substantial grounding-line retreat. We suggest that the grounding-line retreat of Pine Island Glacier, observed between 1992 and 1996, probably commenced sometime after 1981.

scholarly journals Airborne-radar studies: Ice Streams A, B and C, West Antarctica

1993 ◽  
Vol 39 (133) ◽  
pp. 495-506 ◽  
Author(s):  
R. Retzlaff ◽  
N. Lord ◽  
C.R. Bentley
Keyword(s):  
Bottom Topography ◽  
Radar Data ◽  
Temporal Variations ◽  
Surface Elevation ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Ice Streams ◽  
Clear Cut ◽  
Ice Stream ◽  
Ice Stream B

AbstractDigital airborne-radar data were collected during the 1988–89 Antarctic field season in six gridded blocks covering the upstream parts of Ice Streams A, Β and C. An automated processing procedure was developed for picking onset times, converting travel times, interpolating missing data, converting pressure-transducer readings, correcting navigational drift, performing cross-over analysis and zeroing remanent cross-over errors. Cross-over analysis was used to remove the effects of temporal variations in atmospheric pressure and to estimate errors. Interpolation between flight lines was carried out using the Kriging method. Surface elevation was referred to the Rapp Set A geoid by tying the gridded surface to satellite-surveyed ground stations, using a planar-model fit.Maps of surface elevation, ice thickness and bottom topography with standard-error estimates of 4–9 m for surface elevation and 30–60 m for ice thickness and bottom topography were produced. These maps show that the locations of the ice streams are not clearly reflected in either the surface or basal topography, so are presumably controled by basal or internal conditions, that there is no clearly demarcated transition zone between sheet flow and streaming flow, that there is no clear cut evidence for the capture of the catchment of Ice Stream C by Ice Stream B, but that Ice Stream Β does drain virtually the entire region between the lateral boundaries of Ice Streams A and C.

scholarly journals Airborne-radar studies: Ice Streams A, B and C, West Antarctica

1993 ◽  
Vol 39 (133) ◽  
pp. 495-506 ◽  
Author(s):  
R. Retzlaff ◽  
N. Lord ◽  
C.R. Bentley
Keyword(s):  
Bottom Topography ◽  
Radar Data ◽  
Temporal Variations ◽  
Surface Elevation ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Ice Streams ◽  
Clear Cut ◽  
Ice Stream ◽  
Ice Stream B

AbstractDigital airborne-radar data were collected during the 1988–89 Antarctic field season in six gridded blocks covering the upstream parts of Ice Streams A, Β and C. An automated processing procedure was developed for picking onset times, converting travel times, interpolating missing data, converting pressure-transducer readings, correcting navigational drift, performing cross-over analysis and zeroing remanent cross-over errors. Cross-over analysis was used to remove the effects of temporal variations in atmospheric pressure and to estimate errors. Interpolation between flight lines was carried out using the Kriging method. Surface elevation was referred to the Rapp Set A geoid by tying the gridded surface to satellite-surveyed ground stations, using a planar-model fit.Maps of surface elevation, ice thickness and bottom topography with standard-error estimates of 4–9 m for surface elevation and 30–60 m for ice thickness and bottom topography were produced. These maps show that the locations of the ice streams are not clearly reflected in either the surface or basal topography, so are presumably controled by basal or internal conditions, that there is no clearly demarcated transition zone between sheet flow and streaming flow, that there is no clear cut evidence for the capture of the catchment of Ice Stream C by Ice Stream B, but that Ice Stream Β does drain virtually the entire region between the lateral boundaries of Ice Streams A and C.

scholarly journals High-resolution ice thickness and bed topography of a land-terminating section of the Greenland Ice Sheet

2014 ◽  
Vol 7 (1) ◽  
pp. 129-148 ◽  
Author(s):  
K. Lindbäck ◽  
R. Pettersson ◽  
S. H. Doyle ◽  
C. Helanow ◽  
P. Jansson ◽  
...  
Keyword(s):  
Mass Balance ◽  
Sea Level ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Equilibrium Line Altitude ◽  
Bed Topography ◽  
Ice Surface ◽  
Ice Sheet Dynamics

Abstract. We present ice thickness and bed topography maps with high spatial resolution (250 to 500 m) of a and-terminating section of the Greenland Ice Sheet derived from combined ground-based and airborne radar surveys. The data have a total area of ~12000 km2 and cover the whole ablation area of the outlet glaciers of Isunnguata Sermia, Russell, Leverett, Ørkendalen and Isorlersuup up to the long-term mass balance equilibrium line altitude at ~1600 m above sea level. The bed topography shows highly variable subglacial trough systems, and the trough of the Isunnguata Sermia Glacier is over-deepened and reaches an elevation of several hundreds of meters below sea level. The ice surface is smooth and only reflects the bedrock topography in a subtle way, resulting in a highly variable ice thickness. The southern part of our study area consists of higher bed elevations compared to the northern part. The covered area is one of the most studied regions of the Greenland Ice Sheet with studies of mass balance, dynamics, and supraglacial lakes, and our combined dataset can be valuable for detailed studies of ice sheet dynamics and hydrology. The compiled datasets of ground-based and airborne radar surveys are accessible for reviewers (password protected) at doi.pangaea.de/10.1594/pangaea.830314 and will be freely available in the final revised paper.

New ice thickness maps of Filchner–Ronne Ice Shelf, Antarctica, with specific focus on grounding lines and marine ice

2007 ◽  
Vol 19 (4) ◽  
pp. 521-532 ◽  
Author(s):  
A. Lambrecht ◽  
H. Sandhäger ◽  
D.G. Vaughan ◽  
C. Mayer
Keyword(s):  
Surface Elevation ◽  
Small Scale ◽  
Ice Thickness ◽  
Line Position ◽  
Ice Shelf ◽  
Ice Surface ◽  
Seismic Sounding ◽  
Grounding Line ◽  
Data Coverage

AbstractFor the Filchner–Ronne Ice Shelf we have compiled measurements of meteoric ice thickness from many institutions, and several different techniques (e.g. radar and seismic sounding) to produce an improved digital map of meteoric ice thickness. This map has high-resolution compared to previous compilations and serves to highlight small-scale geographic features (e.g. ice plains, grounding-line regions). We have also produced a map of the thickness of marine ice bodies beneath the ice shelf by using borehole density data to calibrate an ice thickness to surface-elevation relation, and then comparing maps of ice surface elevation and meteoric ice thickness to infer marine ice thickness. Due to denser data coverage and the improved density-depth relation, the resulting map is a significant improvement on its predecessors and allows insight into the glaciological context of the ice shelf, in particular, into the location of the grounding lines on the southern Ronne Ice Shelf. Here the data were supplemented with barometric determination of surface elevation, which were used to locate the grounding line position. The final delineation of the grounding line position was confirmed by reference to satellite imagery, and revealed that earlier estimates were substantially in error, especially in the area of Foundation Ice Stream and Möllereisstrom.

scholarly journals Low-frequency radar sounding of ice in East Antarctica and southern Greenland

2014 ◽  
Vol 55 (67) ◽  
pp. 138-146 ◽  
Author(s):  
J. Mouginot ◽  
E. Rignot ◽  
Y. Gim ◽  
D. Kirchner ◽  
E. Le Meur
Keyword(s):  
Low Frequency ◽  
Radar Data ◽  
East Antarctica ◽  
Radar Signal ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Decameter Wavelength ◽  
Radar Sounder ◽  
Thickness Measurements ◽  
Southwest Greenland

AbstractWe discuss a decameter-wavelength airborne radar sounder, the Warm Ice Sounding Explorer (WISE), that provides ice thickness in areas where radar signal penetration at higher frequencies is expected to be limited. Here we report results for three campaigns conducted in Greenland (2008, 2009, 2010) and two in Antarctica (2009, 2010). Comparisons with higher-frequency radar data indicate an accuracy of ±55 m for ice-thickness measurements in Greenland and ±25 m in Antarctica. We also estimate ice thickness of the Qassimiut lobe in southwest Greenland, where few ice-thickness measurements have been made, demonstrating that WISE penetrates in strongly scattering environments.

scholarly journals Basal conditions of two Transantarctic Mountains outlet glaciers from observation-constrained diagnostic modelling

2014 ◽  
Vol 60 (223) ◽  
pp. 855-866 ◽  
Author(s):  
Nicholas R. Golledge ◽  
Oliver J. Marsh ◽  
Wolfgang Rack ◽  
David Braaten ◽  
R. Selwyn Jones
Keyword(s):  
Satellite Images ◽  
Radar Data ◽  
Airborne Radar ◽  
Rate Parameter ◽  
Geothermal Heat ◽  
Ice Surface ◽  
Grounding Line ◽  
Modelling Procedure ◽  
Basal Sliding ◽  
Glacier Flow

AbstractWe present a diagnostic glacier flowline model parameterized and constrained by new velocity data from ice-surface GPS installations and speckle tracking of TerraSAR-X satellite images, newly acquired airborne-radar data, and continental gridded datasets of topography and geothermal heat flux, in order to better understand two outlet glaciers of the East Antarctic ice sheet. Our observational data are employed as primary inputs to a modelling procedure that first calculates the basal thermal regime of each glacier, then iterates the basal sliding coefficient and deformation rate parameter until the fit of simulated to observed surface velocities is optimized. We find that the two glaciers have both frozen and thawed areas at their beds, facilitating partial sliding. Glacier flow arises from a balance between sliding and deformation that fluctuates along the length of each glacier, with the amount of sliding typically varying by up to two orders of magnitude but with deformation rates far more constant. Beardmore Glacier is warmer and faster-flowing than Skelton Glacier, but an up-glacier deepening bed at the grounding line, coupled with ice thicknesses close to flotation, lead us to infer a greater vulnerability of Skelton Glacier to grounding-line recession if affected by ocean-forced thinning and concomitant acceleration.

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.

scholarly journals High-resolution bed topography mapping of Russell Glacier, Greenland, inferred from Operation IceBridge data

2013 ◽  
Vol 59 (218) ◽  
pp. 1015-1023 ◽  
Author(s):  
M. Morlighem ◽  
E. Rignot ◽  
J. Mouginot ◽  
X. Wu ◽  
H. Seroussi ◽  
...  
Keyword(s):  
Mass Conservation ◽  
Radar Data ◽  
Airborne Radar ◽  
Ice Thickness ◽  
Flux Divergence ◽  
Motion Data ◽  
Bed Topography ◽  
Bed Elevation ◽  
Comparable Performance ◽  
Mapping Techniques

AbstractDetailed maps of bed elevation and ice thickness are essential for understanding and projecting the evolution of the ice sheets. Such maps are traditionally obtained using airborne radar-sounding profiler data interpolated onto regular grids using geostatistical tools such as kriging. Here we compare three mapping techniques applied to a dense radar survey of Russell Glacier, West Greenland, by NASA Operation IceBridge: (1) radar tomography (RT) processing of the radar data to map the bed elevation, (2) interpolation of radar-derived thickness by ordinary kriging (KR) and (3) reconstruction of ice thickness based on the principles of mass conservation (MC) combining radar-sounding profiler and ice motion data. RT eliminates ambiguities caused by off-nadir reflections, but is spatially limited. KR yields a standard error in bed elevation of 35 m, but large errors (>300 m a−1) in flux divergence when combined with ice motion data. MC yields a comparable performance in bed elevation mapping, and errors smaller than 1 m a−1 in flux divergence. When the number of radar-sounding tracks is reduced, the performance of KR decreases more rapidly than for MC. Our study site shows that MC is capable of maintaining precision levels of 60 m at 400 m posting with flight tracks separated by 5 km.

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