Wet subglacial bedforms of the NE Greenland Ice Stream shear margins

AbstractWe describe elongate, wet, subglacial bedforms in the shear margins of the NE Greenland Ice Stream and place some constraints on their formation. Lateral shear margin moraines have been observed across the previously glaciated landscape, but little is known about the ice-flow conditions necessary to form these bedforms. Here we describe in situ sediment bedforms under the NE Greenland Ice Stream shear margins that are observed in active-source seismic and ground-penetrating radar surveys. We find bedforms in the shear margins that are ~500 m wide, ~50 m tall, and elongated nearly parallel to ice-flow, including what we believe to be the first subglacial observation of a shear margin moraine. Acoustic impedance analysis of the bedforms shows that they are composed of unconsolidated, deformable, water-saturated till. We use these geophysical observations to place constraints on the possible formation mechanism of these subglacial features.

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Modelling of Kealey Ice Rise, Antarctica, reveals stable ice-flow conditions in East Ellsworth Land over millennia

Journal of Glaciology ◽

10.3189/2014jog13j089 ◽

2014 ◽

Vol 60 (219) ◽

pp. 139-146 ◽

Cited By ~ 14

Author(s):

Carlos Martín ◽

G. Hilmar Gudmundsson ◽

Edward C. King

Keyword(s):

Ground Penetrating Radar ◽

Stationary Flow ◽

Radar Data ◽

Flow Conditions ◽

West Antarctica ◽

Land Area ◽

Ice Flow ◽

Local Conditions ◽

Flow Solver ◽

Ground Penetrating

AbstractFlow at ice divides, their shape, size and internal structure depend not only on local conditions, but also on the flow regimes and past histories of the surrounding ice masses. Here we use field data from Kealey Ice Rise, Ellsworth Land, West Antarctica, in combination with flow modelling to investigate any possible signs of transients in the flow of the surrounding ice masses. Kealey Ice Rise shows linear surface features running parallel to its ridge in satellite imagery and a conspicuous layering in the ground-penetrating radar data known as double-peaked Raymond bumps. Through numerical modelling, by using an anisotropic full-Stokes thermomechanical flow solver, we analyse the evolution of Kealey Ice Rise and the timescales involved. We conclude that the features observed in the stratigraphy of Kealey Ice Rise require at least 3 ka of near-stationary flow conditions. However, we cannot exclude the possibility of a recent flow reorganization in the last century. We stress that the signs of stationary flow in radar stratigraphy observed in Kealey Ice Rise have been observed in other ice divides in the East Ellsworth Land area, suggesting stationary flow conditions over a millennial timescale in the region.

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Combination of ground penetrating radar and seismic surveys of the tailings dam

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/938/1/012020 ◽

2021 ◽

Vol 938 (1) ◽

pp. 012020

Author(s):

A Kalashnik ◽

A Dyakov

Keyword(s):

Internal Structure ◽

Ground Penetrating Radar ◽

Water Saturation ◽

The Body ◽

Tailings Dam ◽

Geophysical Surveys ◽

In Situ Experiments ◽

Water Saturated ◽

Ground Penetrating

Abstract Identification of water-saturated zones in the tailings dams is an actual scientific and practical task in terms of providing, first of all, their mechanical strength and filtration stability. Use of active sounding geophysical study methods allows obtaining sufficiently detailed information about the peculiarities of the internal structure of the tailings dam and the degree of water saturation of the composing soils. The paper presents the results of in-situ experiments on the study of the tailings dam of the mining enterprise by ground penetrating radar (GPR) and seismic methods. A comparative analysis of the conducted studies has allowed clarifying the internal structure and assessing the dam’s condition, paying special attention to the identification of local zones of increased water saturation and filtration. Based on the calculated correlation coefficient of electromagnetic and seismic wave velocity values, it was revealed that synchronization of geophysical surveys allows significantly increasing the reliability of in-situ determinations, as well as obtaining more reliable data. The results of the studies are the basis for predicting the most vulnerable places (zones) of a bulk ground hydraulic facility, as well as the localization of water-saturated areas in the body of the ground structures with greater reliability and performance.

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An Automatic Processing Framework for In Situ Determination of Ecohydrological Root Water Content by Ground-Penetrating Radar

IEEE Transactions on Geoscience and Remote Sensing ◽

10.1109/tgrs.2021.3065066 ◽

2021 ◽

pp. 1-15

Author(s):

Xinbo Liu ◽

Li Guo ◽

Xihong Cui ◽

John R. Butnor ◽

Elizabeth W. Boyer ◽

...

Keyword(s):

Water Content ◽

Ground Penetrating Radar ◽

Automatic Processing ◽

Ground Penetrating ◽

Processing Framework

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Identifying Spatial and Temporal Variations in Concrete Bridges with Ground Penetrating Radar Attributes

Remote Sensing ◽

10.3390/rs13091846 ◽

2021 ◽

Vol 13 (9) ◽

pp. 1846

Author(s):

Vivek Kumar ◽

Isabel M. Morris ◽

Santiago A. Lopez ◽

Branko Glisic

Keyword(s):

Compressive Strength ◽

Ground Penetrating Radar ◽

Material Properties ◽

Temporal Variations ◽

Concrete Bridges ◽

Spatial And Temporal Variation ◽

Reflected Waves ◽

Ground Penetrating ◽

Over Time

Estimating variations in material properties over space and time is essential for the purposes of structural health monitoring (SHM), mandated inspection, and insurance of civil infrastructure. Properties such as compressive strength evolve over time and are reflective of the overall condition of the aging infrastructure. Concrete structures pose an additional challenge due to the inherent spatial variability of material properties over large length scales. In recent years, nondestructive approaches such as rebound hammer and ultrasonic velocity have been used to determine the in situ material properties of concrete with a focus on the compressive strength. However, these methods require personnel expertise, careful data collection, and high investment. This paper presents a novel approach using ground penetrating radar (GPR) to estimate the variability of in situ material properties over time and space for assessment of concrete bridges. The results show that attributes (or features) of the GPR data such as raw average amplitudes can be used to identify differences in compressive strength across the deck of a concrete bridge. Attributes such as instantaneous amplitudes and intensity of reflected waves are useful in predicting the material properties such as compressive strength, porosity, and density. For compressive strength, one alternative approach of the Maturity Index (MI) was used to estimate the present values and compare with GPR estimated values. The results show that GPR attributes could be successfully used for identifying spatial and temporal variation of concrete properties. Finally, discussions are presented regarding their suitability and limitations for field applications.

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Ground-penetrating radar profiles of the McMurdo Shear Zone, Antarctica, acquired with an unmanned rover: Interpretation of crevasses, fractures, and folds within firn and marine ice

Geophysics ◽

10.1190/geo2015-0132.1 ◽

2016 ◽

Vol 81 (1) ◽

pp. WA21-WA34 ◽

Cited By ~ 9

Author(s):

Steven A. Arcone ◽

James H. Lever ◽

Laura E. Ray ◽

Benjamin S. Walker ◽

Gordon Hamilton ◽

...

Keyword(s):

Shear Zone ◽

Ground Penetrating Radar ◽

Ice Accretion ◽

Ice Shelf ◽

Ice Flow ◽

Ross Ice Shelf ◽

Robotic Vehicle ◽

Ground Penetrating ◽

Depth Ranges ◽

Radar Antennas

The crevassed firn of the McMurdo shear zone (SZ) within the Ross Ice Shelf may also contain crevasses deep within its meteoric and marine ice, but the surface crevassing prevents ordinary vehicle access to investigate its structure geophysically. We used a lightweight robotic vehicle to tow 200- and 400-MHz ground-penetrating radar antennas simultaneously along 100 parallel transects over a [Formula: see text] grid spanning the SZ width. Transects were generally orthogonal to the ice flow. Total firn and meteoric ice thickness was approximately 160 m. Firn crevasses profiled at 400 MHz were up to 16 m wide, under snow bridges up to 10 m thick, and with strikes near 35°–40° to the transect direction. From the top down, 200-MHz profiles revealed firn diffractions originating to a depth of approximately 40 m, no discernible structure within the meteoric ice, a discontinuous transitional horizon, and at least 20 m of stratified marine ice; 28–31 m of freeboard found more marine ice exists. Based on 10 consecutive transects covering approximately [Formula: see text], we preliminarily interpreted the transitional horizon to be a thin saline layer, and marine ice hyperbolic diffractions and reflections to be responses to localized fractures, and crevasses filled with unstratified marine ice, all at strikes from 27° to 50°. We preliminarily interpreted off-nadir, marine ice horizons to be responses to linear and folded faults, similar to some in firn. The coinciding and synchronously folded areas of fractured firn and marine ice suggested that the visibly unstructured meteoric ice beneath our grid was also fractured, but either never crevassed, crevassed and sutured without marine ice inclusions, or that any ice containing crevasses might have eroded before marine ice accretion. We will test these interpretations with analysis of all transects and by extending our grid and increasing our depth ranges.

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IN-SITU CASSAVA ROOT SIZE MEASUREMENT USING GROUND PENETRATING RADAR (GPR)

10.4133/sageep.31-030 ◽

2018 ◽

Author(s):

Timothy H. Larson ◽

Riley J. Balikian ◽

Ursula Ruiz-Vera ◽

Donald Ort

Keyword(s):

Ground Penetrating Radar ◽

Size Measurement ◽

Cassava Root ◽

Ground Penetrating ◽

Root Size

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Velocity pattern in a transect across Ice Stream B, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000016452 ◽

1993 ◽

Vol 39 (133) ◽

pp. 562-572 ◽

Cited By ~ 4

Author(s):

I. M. Whillans ◽

M. Jackson ◽

Y-H. Tseng

Keyword(s):

Aerial Photography ◽

Lateral Shear ◽

Ice Flow ◽

Measured Velocity ◽

Velocity Gradients ◽

Spreading Ridges ◽

Ice Stream ◽

Surface Slopes ◽

Fast Ice ◽

Ice Stream B

AbstractRepeat aerial photography is used to obtain closely spaced measurements of velocity and elevation over a complete transect of Ice Stream tributary B2, including the shear margins, the fast ice of the ice stream and several unusual features, as well as the UpB camp. Persistent features, mainly crevasses, are tracked to provide 1541 values of velocity and 1933 values of elevation. These are used to describe ice flow in the ice stream. Within the ice stream, the dominant velocity gradient is lateral shear. Crevasse patterns are studied in relation to measured velocity gradients. Crevasses intersect one another at acute angles, indicating that their origin is deeper than the depth to which crevasses penetrate. One feature within the ice stream seems to be a raft of stiff ice. Others are crevasse trains. Also, there are spreading ridges, perhaps due to upwelling ice. There is no evidence of large sticky spots within the studied transect, i.e. no steep surface slopes with associated surface stretching just up-glacier and surface compression down-glacier.

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In Situ Detection of Tree Root Systems under Heterogeneous Anthropogenic Soil Conditions Using Ground Penetrating Radar

Journal of Infrastructure Systems ◽

10.1061/(asce)is.1943-555x.0000501 ◽

2019 ◽

Vol 25 (3) ◽

pp. 05019008 ◽

Cited By ~ 1

Author(s):

D. Altdorff ◽

J. Botschek ◽

M. Honds ◽

J. van der Kruk ◽

H. Vereecken

Keyword(s):

Ground Penetrating Radar ◽

Root Systems ◽

Soil Conditions ◽

Anthropogenic Soil ◽

Ground Penetrating ◽

In Situ Detection

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Accounting for Surface Roughness Scattering in the Characterization of Forest Litter with Ground-Penetrating Radar

Remote Sensing ◽

10.3390/rs11070828 ◽

2019 ◽

Vol 11 (7) ◽

pp. 828

Author(s):

Frédéric André ◽

François Jonard ◽

Mathieu Jonard ◽

Harry Vereecken ◽

Sébastien Lambot

Keyword(s):

Surface Roughness ◽

Ground Penetrating Radar ◽

Land Surface ◽

Forest Litter ◽

Relative Dielectric Permittivity ◽

In Situ Experiment ◽

In Situ Experiments ◽

Ground Penetrating

Accurate characterization of forest litter is of high interest for land surface modeling and for interpreting remote sensing observations over forested areas. Due to the large spatial heterogeneity of forest litter, scattering from litter layers has to be considered when sensed using microwave techniques. Here, we apply a full-waveform radar model combined with a surface roughness model to ultrawideband ground-penetrating radar (GPR) data acquired above forest litter during controlled and in situ experiments. For both experiments, the proposed modeling approach successfully described the radar data, with improvements compared to a previous study in which roughness was not directly accounted for. Inversion of the GPR data also provided reliable estimates of the relative dielectric permittivity of the recently fallen litter (OL layer) and of the fragmented litter in partial decomposition (OF layer) with, respectively, averaged values of 1.35 and 3.8 for the controlled experiment and of 3.9 and 7.5 for the in situ experiment. These results show the promising potentialities of GPR for efficient and non-invasive characterization of forest organic layers.

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