scholarly journals Bed properties and hydrological conditions underneath McCall Glacier, Alaska, USA

2009 ◽  
Vol 50 (51) ◽  
pp. 80-84 ◽  
Author(s):  
Frank Pattyn ◽  
Charlotte Delcourt ◽  
Denis Samyn ◽  
Bert de Smedt ◽  
Matt Nolan
Keyword(s):  
Potential Gradient ◽  
Ice Thickness ◽  
Central Frequency ◽  
Bed Topography ◽  
Ice Volume ◽  
Arctic Alaska ◽  
Digital Elevation ◽  
Basal Sliding ◽  
Radio Echo Sounding ◽  
Elevation Model

AbstractDuring three summer field seasons (2003, 2005 and 2006) we carried out radio-echo sounding measurements with a 5MHz (central frequency) ice-penetrating radar on McCall Glacier, Arctic Alaska, USA, along the central flowline and 17 cross-profiles. Two-way travel time was, after migration, converted to ice thickness, which, in combination with a recent digital elevation model of the surface of the glaciated area, resulted in a detailed map of the bed topography. This reveals a complex basal topography in the confluence area of the different glacial cirques. The pattern of subglacial water flow following the hydraulic potential gradient was calculated for the whole glacier area and shows a confluence of subglacial water downstream from the confluence of the glacier cirques. From the ice-thickness map the total ice volume was estimated as slightly less than 0.5 km3. Bed reflection power (BRP) was determined for the glacier after correction for ice-thickness dependence. Results reveal a clear relationship between the BRP pattern and basal sliding anomalies along the central flowline.

scholarly journals Subglacial landforms beneath Rutford Ice Stream, Antarctica: detailed bed topography from ice-penetrating radar

2015 ◽  
Vol 8 (2) ◽  
pp. 913-934
Author(s):  
E. C. King ◽  
H. D. Pritchard ◽  
A. M. Smith
Keyword(s):  
Surface Elevation ◽  
Baseline Survey ◽  
Polar Regions ◽  
Active System ◽  
Bed Topography ◽  
Ice Stream ◽  
Digital Elevation ◽  
Elevation Data ◽  
Radio Echo Sounding ◽  
Elevation Model

Abstract. We present a digital elevation model of the bed of Rutford Ice Stream, Antarctica derived from radio-echo sounding data. The data cover an 18 km × 40 km area immediately upstream of the grounding line of the ice stream. This area is of particular interest because repeated seismic surveys have shown that rapid erosion and deposition of subglacial sediments has taken place. The bed topography shows a range of different subglacial landforms including mega-scale glacial lineations, drumlins and hummocks. This dataset will form a baseline survey which, when compared to future surveys, should reveal how active subglacial landscapes change over time. These data also allow comparison between subglacial landforms in an active system with those observed in deglaciated areas in both polar regions. The dataset comprises observed ice thickness data, an interpolated bed elevation grid, observed surface elevation data and a surface elevation grid. The dataset is available at http://doi.org/269.

scholarly journals Assessment of evolution and risks of glacier lake outbursts in the Djungarskiy Alatau, Central Asia, using Landsat imagery and glacier bed topography modelling

2017 ◽  
Vol 17 (10) ◽  
pp. 1837-1856 ◽  
Author(s):  
Vassiliy Kapitsa ◽  
Maria Shahgedanova ◽  
Horst Machguth ◽  
Igor Severskiy ◽  
Akhmetkal Medeu
Keyword(s):  
Landsat Imagery ◽  
Shuttle Radar Topography Mission ◽  
Ice Thickness ◽  
Srtm Dem ◽  
Hazard Management ◽  
Bed Topography ◽  
Digital Elevation ◽  
Uncertainty Of Measurements ◽  
Subglacial Topography ◽  
Elevation Model

Abstract. Changes in the abundance and area of mountain lakes in the Djungarskiy (Jetysu) Alatau between 2002 and 2014 were investigated using Landsat imagery. The number of lakes increased by 6.2 % from 599 to 636 with a growth rate of 0.51 % a−1. The combined areas were 16.26 ± 0.85 to 17.35 ± 0.92 km2 respectively and the overall change was within the uncertainty of measurements. Fifty lakes, whose potential outburst can damage existing infrastructure, were identified. The glacier bed topography version 2 (GlabTop2) model was applied to simulate ice thickness and subglacial topography using glacier outlines for 2000 and SRTM DEM (Shuttle Radar Topography Mission digital elevation model) as input data achieving realistic patterns of ice thickness. A total of 513 overdeepenings in the modelled glacier beds, presenting potential sites for the development of lakes, were identified with a combined area of 14.7 km2. Morphometric parameters of the modelled overdeepenings were close to those of the existing lakes. A comparison of locations of the overdeepenings and newly formed lakes in the areas de-glacierized in 2000–2014 showed that 67 % of the lakes developed at the sites of the overdeepenings. The rates of increase in areas of new lakes correlated with areas of modelled overdeepenings. Locations where hazardous lakes may develop in the future were identified. The GlabTop2 approach is shown to be a useful tool in hazard management providing data on the potential evolution of future lakes.

scholarly journals Revisiting Austfonna, Svalbard, with potential field methods – a new characterization of the bed topography and its physical properties

2020 ◽  
Vol 14 (1) ◽  
pp. 183-197
Author(s):  
Marie-Andrée Dumais ◽  
Marco Brönner
Keyword(s):  
Physical Properties ◽  
Potential Field ◽  
Gravity Data ◽  
Magnetic Data ◽  
Airborne Gravity ◽  
Ice Thickness ◽  
Field Methods ◽  
Bed Topography ◽  
Basal Sliding ◽  
Radio Echo Sounding

Abstract. With hundreds of metres of ice, the bedrock underlying Austfonna, the largest icecap on Svalbard, is hard to characterize in terms of topography and physical properties. Ground-penetrating radar (GPR) measurements supply ice thickness estimation, but the data quality is temperature dependent, leading to uncertainties. To remedy this, we include airborne gravity measurements. With a significant density contrast between ice and bedrock, subglacial bed topography is effectively derived from gravity modelling. While the ice thickness model relies primarily on the gravity data, integrating airborne magnetic data provides an extra insight into the basement distribution. This contributes to refining the range of density expected under the ice and improving the subice model. For this study, a prominent magmatic north–south-oriented intrusion and the presence of carbonates are assessed. The results reveal the complexity of the subsurface lithology, characterized by different basement affinities. With the geophysical parameters of the bedrock determined, a new bed topography is extracted and adjusted for the potential field interpretation, i.e. magnetic- and gravity-data analysis and modelling. When the results are compared to bed elevation maps previously produced by radio-echo sounding (RES) and GPR data, the discrepancies are pronounced where the RES and GPR data are scarce. Hence, areas with limited coverage are addressed with the potential field interpretation, increasing the accuracy of the overall bed topography. In addition, the methodology improves understanding of the geology; assigns physical properties to the basements; and reveals the presence of softer bed, carbonates and magmatic intrusions under Austfonna, which influence the basal-sliding rates and surges.

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 Measuring and inferring the ice thickness distribution of four glaciers in the Tien Shan, Kyrgyzstan

2020 ◽  
pp. 1-18
Author(s):  
Lander Van Tricht ◽  
Philippe Huybrechts ◽  
Jonas Van Breedam ◽  
Johannes J. Fürst ◽  
Oleg Rybak ◽  
...  
Keyword(s):  
Cross Validation ◽  
Thickness Distribution ◽  
Tien Shan ◽  
Ice Thickness ◽  
Ice Volume ◽  
In Situ Data ◽  
Radio Echo Sounding ◽  
Thickness Measurements ◽  
Tien Shan Mountains

Abstract Glaciers in the Tien Shan mountains contribute considerably to the fresh water used for irrigation, households and energy supply in the dry lowland areas of Kyrgyzstan and its neighbouring countries. To date, reconstructions of the current ice volume and ice thickness distribution remain scarce, and accurate data are largely lacking at the local scale. Here, we present a detailed ice thickness distribution of Ashu-Tor, Bordu, Golubin and Kara-Batkak glaciers derived from radio-echo sounding measurements and modelling. All the ice thickness measurements are used to calibrate three individual models to estimate the ice thickness in inaccessible areas. A cross-validation between modelled and measured ice thickness for a subset of the data is performed to attribute a weight to every model and to assemble a final composite ice thickness distribution for every glacier. Results reveal the thickest ice on Ashu-Tor glacier with values up to 201 ± 12 m. The ice thickness measurements and distributions are also compared with estimates composed without the use of in situ data. These estimates approach the total ice volume well, but local ice thicknesses vary substantially.

Estimating the ice thickness of the Müller Ice Cap using an inversion of the shallow ice approximation

2021 ◽  
Author(s):  
Ann-Sofie Priergaard Zinck ◽  
Aslak Grinsted
Keyword(s):  
Remote Sensing Data ◽  
The Arctic ◽  
Ice Thickness ◽  
Potential Contribution ◽  
Mean Squared Errors ◽  
Ice Caps ◽  
Ice Cap ◽  
Regression Parameters ◽  
Digital Elevation ◽  
Elevation Model

<p><span>The ice thickness of the Müller Ice Cap, Arctic Canada, is estimated using regression parameters obtained from an inversion of the shallow ice approximation by the use of a single Operation IceBridge flight line in combination with the glacier outline, surface slope, and elevation. The model is compared with an iterative inverse method of estimating the bedrock topography using PISM as a forward model. In both models the surface elevation is given by the Arctic Digital Elevation Model. The root mean squared errors of the ice thickness on the ice cap is 131 m and 139 m for the shallow ice inversion and the PISM model, respectively. Including the outlet glaciers increases the root mean squared errors to 136 m and 396 m, respectively. </span></p><p><span>The simplicity of the shallow ice inversion model, combined with the good results and the fact that only remote sensing data is needed, means that there is a possibility of applying this model in a global glacier thickness estimate by using the Randolph Glacier Inventory. Most global glacier estimates only provide the volume and not the ice thickness of the glaciers. Hence, global ice thickness models is of great importance in quantifying the potential contribution of sea level rise from the glaciers and ice caps around the globe. </span></p>

scholarly journals Helicopter-borne radio-echo sounding of Svartisen, Norway

1993 ◽  
Vol 17 ◽  
pp. 23-26 ◽  
Author(s):  
Michael Kennett ◽  
Tron Laumann ◽  
Cecilie Lund
Keyword(s):  
Low Frequency ◽  
Ice Thickness ◽  
Digital Receiver ◽  
Outlet Glacier ◽  
Northern Norway ◽  
Bed Topography ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Depth Sounding ◽  
Ice Radar

A helicopter-mounted low frequency ice-radar has been developed for the depth sounding of temperate glaciers. The radar consists of standard transmitter and digital receiver equipment. The long antennae are supported on a special aluminium and fibreglass construction which hangs 20 m below the helicopter. The radar has been used on Engabreen, an outlet glacier of the Svartisen Ice Cap in northern Norway, where ice thicknesses of up to 350 m were obtained. The results have been used to construct a map of bed topography of the lower part of Engabreen. This map is largely consistent with ice thickness data obtained by drilling.

scholarly journals Topography and dynamics of Austfonna, Nordaustlandet, Svalbard, from SAR interferometry

1997 ◽  
Vol 24 ◽  
pp. 403-408 ◽  
Author(s):  
Beverley Unwin ◽  
Duncan Wingham
Keyword(s):  
Sar Interferometry ◽  
Synthetic Aperture ◽  
Drainage Basins ◽  
Ice Caps ◽  
Radar Images ◽  
Differential Interferometry ◽  
Digital Elevation ◽  
Radio Echo Sounding ◽  
Velocity Information ◽  
Elevation Model

The ice caps of Nordaustlandet, Svalbard, represent one of the largest glaciated areas outside of Antarctica and Greenland. They demonstrate a variety of different flow regimes within a comparatively compact area. We report on the first interferometrically derived elevation models and velocity visualisations of Austfonna. This initial investigation had three purposes: to determine whether the coherence and velocity characteristics of the region permitted interferometric survey; to determine the accuracy of derived elevations; and to assess the possibility of investigating time-variant flow of the more dynamic ice bodies using differential interferometry. A trio of coherent synthetic aperture radar images from ERS-1 ’s First Ice Phase was identified. The images were combined to separate the topographic and velocity components of the resultant interferograms. The topographic phase difference was used to produce a digital elevation model of Austfonna. Its accuracy relative to radio-echo-sounding derived tie-points is 8 m and its resolution 40 m. We also present synoptic views of the velocity field of three of Austfonna’s drainage basins, and comment on the extraction of useful velocity information.

scholarly journals New maps of the ice thickness and subglacial topography in Dronning Maud Land, Antarctica, determined by means of airborne radio-echo sounding

1999 ◽  
Vol 29 ◽  
pp. 267-272 ◽  
Author(s):  
D. Steinhage ◽  
U. Nixdorf ◽  
U. Meyer ◽  
H. Miller
Keyword(s):  
Three Dimensional ◽  
Austral Summer ◽  
Ice Thickness ◽  
Ice Volume ◽  
Site Survey ◽  
Radio Echo Sounding ◽  
First Results ◽  
Dronning Maud Land ◽  
Subglacial Topography ◽  
Echo Sounding

AbstractSince the austral summer of 1994-95 the Alfred Wegener Institute has carried out airborne radio-echo sounding (RES) measurements in Antarctica with its newly designed RES system. Since 1995-96 an ongoing pre-site survey for an ice-coring drill site in Dronning Maud Land has been carried out as part of the European Project for Ice Goring in Antarctica. The survey covers an area of 948 000 km2, with >49 500 km of airborne RES obtained from >200 hours of flight operation flown during the period 1994-97. In this paper, first results of the airborne RES survey are graphically summarized as newly derived maps of the ice thickness and subglacial topography, as well as a three-dimensional view of surface and subglacial bed and outcrop topography, revealing a total ice volume of 1.48 x 106 km3.

scholarly journals A multi-level strategy for anticipating future glacier lake formation and associated hazard potentials

2010 ◽  
Vol 10 (2) ◽  
pp. 339-352 ◽  
Author(s):  
H. Frey ◽  
W. Haeberli ◽  
A. Linsbauer ◽  
C. Huggel ◽  
F. Paul
Keyword(s):  
Swiss Alps ◽  
Bed Topography ◽  
Aster Gdem ◽  
Digital Elevation ◽  
Lake Formation ◽  
Level 3 ◽  
Multi Level ◽  
Four Levels ◽  
Elevation Model

Abstract. In the course of glacier retreat, new glacier lakes can develop. As such lakes can be a source of natural hazards, strategies for predicting future glacier lake formation are important for an early planning of safety measures. In this article, a multi-level strategy for the identification of overdeepened parts of the glacier beds and, hence, sites with potential future lake formation, is presented. At the first two of the four levels of this strategy, glacier bed overdeepenings are estimated qualitatively and over large regions based on a digital elevation model (DEM) and digital glacier outlines. On level 3, more detailed and laborious models are applied for modeling the glacier bed topography over smaller regions; and on level 4, special situations must be investigated in-situ with detailed measurements such as geophysical soundings. The approaches of the strategy are validated using historical data from Trift Glacier, where a lake formed over the past decade. Scenarios of future glacier lakes are shown for the two test regions Aletsch and Bernina in the Swiss Alps. In the Bernina region, potential future lake outbursts are modeled, using a GIS-based hydrological flow routing model. As shown by a corresponding test, the ASTER GDEM and the SRTM DEM are both suitable to be used within the proposed strategy. Application of this strategy in other mountain regions of the world is therefore possible as well.

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