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.

scholarly journals Ice thickness distribution of all Swiss glaciers based on extended ground-penetrating radar data and glaciological modeling

2021 ◽  
pp. 1-19
Author(s):  
Melchior Grab ◽  
Enrico Mattea ◽  
Andreas Bauder ◽  
Matthias Huss ◽  
Lasse Rabenstein ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Thickness Distribution ◽  
Radar Data ◽  
Tourism Industry ◽  
Swiss Alps ◽  
Ice Thickness ◽  
Hazard Management ◽  
Bed Topography ◽  
Ice Volume ◽  
Ground Penetrating

Abstract Accurate knowledge of the ice thickness distribution and glacier bed topography is essential for predicting dynamic glacier changes and the future developments of downstream hydrology, which are impacting the energy sector, tourism industry and natural hazard management. Using AIR-ETH, a new helicopter-borne ground-penetrating radar (GPR) platform, we measured the ice thickness of all large and most medium-sized glaciers in the Swiss Alps during the years 2016–20. Most of these had either never or only partially been surveyed before. With this new dataset, 251 glaciers – making up 81% of the glacierized area – are now covered by GPR surveys. For obtaining a comprehensive estimate of the overall glacier ice volume, ice thickness distribution and glacier bed topography, we combined this large amount of data with two independent modeling algorithms. This resulted in new maps of the glacier bed topography with unprecedented accuracy. The total glacier volume in the Swiss Alps was determined to be 58.7 ± 2.5 km3 in the year 2016. By projecting these results based on mass-balance data, we estimated a total ice volume of 52.9 ± 2.7 km3 for the year 2020. Data and modeling results are accessible in the form of the SwissGlacierThickness-R2020 data package.

scholarly journals High-resolution ice-thickness mapping in South Greenland

2014 ◽  
Vol 55 (67) ◽  
pp. 64-70 ◽  
Author(s):  
M. Morlighem ◽  
E. Rignot ◽  
J. Mouginot ◽  
H. Seroussi ◽  
E. Larour
Keyword(s):  
High Resolution ◽  
Optimization Problems ◽  
Mass Conservation ◽  
Ice Thickness ◽  
Soft Constraint ◽  
Hard Constraint ◽  
Conservation Of Mass ◽  
Motion Data ◽  
Geostatistical Techniques ◽  
Thickness Measurements

AbstractAirborne radar sounding is difficult in South Greenland because of the presence of englacial water, which prevents the signal from reaching the bed. Data coverage remains suboptimal for traditional methods of ice-thickness and bed mapping that rely on geostatistical techniques, such as kriging, because important features are missing. Here we apply two alternative approaches of high-resolution (~300m) ice-thickness mapping, that are based on the conservation of mass, to two regions of South Greenland: (1) Qooqqup Sermia and Kiattuut Sermiat, and (2) Ikertivaq. These two algorithms solve optimization problems, for which the conservation of mass is either enforced as a hard constraint, or as a soft constraint. For the first region, very few measurements are available but there is no gap in ice motion data, whereas for Ikertivaq, more ice-thickness measurements are available, but there are gaps in ice motion data. We show that mass-conservation algorithms can be used as validation tools for radar sounding. We also show that it is preferable to apply mass conservation as a hard constraint, rather than a soft constraint, as it better preserves elongated features, such as glacial valleys and ridges.

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.

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 Stochastic modeling of subglacial topography exposes uncertainty in water routing at Jakobshavn Glacier

2020 ◽  
pp. 1-9
Author(s):  
Emma J. MacKie ◽  
Dustin M. Schroeder ◽  
Chen Zuo ◽  
Zhen Yin ◽  
Jef Caers
Keyword(s):  
Mass Conservation ◽  
Simulation Method ◽  
Radar Data ◽  
Geostatistical Simulation ◽  
Ice Flow ◽  
Bed Topography ◽  
Drainage Patterns ◽  
Secondary Constraint ◽  
Subglacial Topography ◽  
Data Coverage

Abstract Subglacial topography is an important feature in numerous ice-sheet analyses and can drive the routing of water at the bed. Bed topography is primarily measured with ice-penetrating radar. Significant gaps, however, remain in data coverage that require interpolation. Topographic interpolations are typically made with kriging, as well as with mass conservation, where ice flow dynamics are used to constrain bed geometry. However, these techniques generate bed topography that is unrealistically smooth at small scales, which biases subglacial water flowpath models and makes it difficult to rigorously quantify uncertainty in subglacial drainage patterns. To address this challenge, we adapt a geostatistical simulation method with probabilistic modeling to stochastically simulate bed topography such that the interpolated topography retains the spatial statistics of the ice-penetrating radar data. We use this method to simulate subglacial topography using mass conservation topography as a secondary constraint. We apply a water routing model to each of these realizations. Our results show that many of the flowpaths significantly change with each topographic realization, demonstrating that geostatistical simulation can be useful for assessing confidence in subglacial flowpaths.

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 Modelling glacier-bed overdeepenings and possible future lakes for the glaciers in the Himalaya—Karakoram region

2016 ◽  
Vol 57 (71) ◽  
pp. 119-130 ◽  
Author(s):  
A. Linsbauer ◽  
H. Frey ◽  
W. Haeberli ◽  
H. Machguth ◽  
M.F. Azam ◽  
...  
Keyword(s):  
Ice Thickness ◽  
Surface Slope ◽  
Bed Topography ◽  
Bed Elevation ◽  
Digital Elevation ◽  
Surface Slopes ◽  
Lake Formation ◽  
Topography Model ◽  
Basal Shear ◽  
The Himalaya

AbstractSurface digital elevation models (DEMs) and slope-related estimates of glacier thickness enable modelling of glacier-bed topographies over large ice-covered areas. Due to the erosive power of glaciers, such bed topographies can contain numerous overdeepenings, which when exposed following glacier retreat may fill with water and form new lakes. In this study, the bed overdeepenings for ~28 000 glaciers (40 775 km2) of the Himalaya-Karakoram region are modelled using GlabTop2 (Glacier Bed Topography model version 2), in which ice thickness is inferred from surface slope by parameterizing basal shear stress as a function of elevation range for each glacier. The modelled ice thicknesses are uncertain (±30%), but spatial patterns of ice thickness and bed elevation primarily depend on surface slopes as derived from the DEM and, hence, are more robust. About 16 000 overdeepenings larger than 104m2 were detected in the modelled glacier beds, covering an area of ~2200 km2 and having a volume of ~120km3 (3-4% of present-day glacier volume). About 5000 of these overdeepenings (1800 km2) have a volume larger than 106m3. The results presented here are useful for anticipating landscape evolution and potential future lake formation with associated opportunities (tourism, hydropower) and risks (lake outbursts).

scholarly journals Inverting ice surface elevation and velocity for bed topography and slipperiness beneath Thwaites Glacier

2021 ◽  
Author(s):  
Helen Ockenden ◽  
Robert G. Bingham ◽  
Andrew Curtis ◽  
Daniel Goldberg
Keyword(s):  
High Resolution ◽  
Ice Sheets ◽  
Mass Conservation ◽  
Radar Data ◽  
Surface Flow ◽  
Surface Elevation ◽  
Linear Perturbation ◽  
Detailed Knowledge ◽  
Bed Topography ◽  
Ice Stream

Abstract. There is significant uncertainty over how ice sheets and glaciers will respond to rising global temperatures. Limited knowledge of the topography and rheology of ice-bed interface is a key cause of this uncertainty, as models show that small changes in the bed can have a large influence on predicted rates of ice loss. Most of our detailed knowledge of bed topography comes from airborne and ground-penetrating radar observations. However, these direct observations are not spaced closely enough to meet the requirements of ice-sheet models, so interpolation and inversion methods are used to fill in the gaps. Here we present the results of a new inversion of surface-elevation and velocity data over Thwaites Glacier, West Antarctica, for bed topography and slipperiness (i.e. the degree of basal slip for a given level of drag). The inversion is based on a steady-state linear perturbation analysis of the shallow-ice-stream equations. The method works by identifying disturbances to surface flow which are caused by obstacles or sticky patches in the bed, and can therefore be applied wherever the shallow-ice-stream equations hold and where surface data are available, even where the ice thickness is not well known. We assess the performance of the inversion for topography with the available radar data. Although the topographic output from the inversion is less successful where the bed slopes steeply, it compares well with radar data from the central trunk of the glacier. This method could therefore be useful as either an independent test of other interpolation methods such as mass conservation and kriging, or as a complementary technique in regions where those techniques fail. We do not have data to allow us to assess the success of the slipperiness results from our inversions, but we provide maps that may guide future seismic data collection across Thwaites Glacier. The methods presented here show significant promise for using high-resolution satellite datasets, calibrated by the sparser field datasets, to generate high resolution bed topography products across the ice sheets, and therefore contribute to reduced uncertainty in predictions of future sea-level rise.

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.

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