scholarly journals Glacier naled evolution and relation to the subglacial drainage system based on water chemistry and GPR surveys (Werenskioldbreen, SW Svalbard)

2016 ◽  
Vol 57 (72) ◽  
pp. 19-30 ◽  
Author(s):  
Łukasz Stachnik ◽  
Jacob C. Yde ◽  
Marta Kondracka ◽  
Dariusz Ignatiuk ◽  
Magdalena Grzesik
Keyword(s):  
Ground Penetrating Radar ◽  
Chemical Weathering ◽  
Drainage System ◽  
Carbonate Dissolution ◽  
Drainage Pattern ◽  
Sulphide Oxidation ◽  
High Carbonate ◽  
Polythermal Glacier ◽  
Ground Penetrating ◽  
Subglacial Drainage

ABSTRACTGlacier naledi are extrusive ice masses that appear in front of glaciers as a consequence of refreezing of meltwater seepage during the accumulation season. These structures provide a unique opportunity to understand subglacial drainage activity during the accumulation season; however, only few detailed studies have previously focused on their characteristics. Here, we investigated glacier-derived naled assemblages in the proglacial zone of the polythermal glacier Werenskioldbreen (27.4 km2) in SW Svalbard. We determined the spatial distribution of naledi using ground penetrating radar surveys. The main subglacial drainage pattern was related to a channel under the medial moraine, and three sources are linked to a distributed subglacial drainage network. The relation between atmospherically-corrected (Ca2+ + Mg2+) and (SO42−) in sub-naled waters was closely related to sulphide oxidation coupled with carbonate dissolution (r = 0.99; slope = 1.6). This is consistent with the local lithology, which is dominated by schist containing carbonates. We also found high carbonate saturation indices in pale white ice layers within the naled. We conclude that sulphide oxidation coupled with carbonate dissolution is the dominant chemical weathering process in the subglacial drainage system of Werenskioldbreen during the accumulation season.

scholarly journals Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by Ground Penetrating Radar

2010 ◽  
Vol 4 (4) ◽  
pp. 2169-2199
Author(s):  
K. Bælum ◽  
D. I. Benn
Keyword(s):  
Ground Penetrating Radar ◽  
Thermal Structure ◽  
Drainage System ◽  
High Arctic ◽  
Differential Gps ◽  
Glacier Surface ◽  
Drainage Channels ◽  
Polythermal Glacier ◽  
Ground Penetrating ◽  
Subglacial Drainage

Abstract. Proglacial icings accumulate in front of many High Arctic glaciers during the winter months, as water escapes from englacial or subglacial storage. Such icings have been interpreted as evidence for warm-based subglacial conditions, but several are now known to occur in front of cold-based glaciers. In this study, we investigate the drainage system of Tellbreen, a 3.5 km long cold-based polythermal glacier in central Spitsbergen, where a large proglacial icing develops each winter, to determine the location and geometry of storage elements. DEMs of the glacier surface and bed were constructed using maps, differential GPS and GPR. Patterns of surface lowering indicate that the glacier has a long-term mass balance of −0.6 ± 0.2 m/year. Englacial and subglacial drainage channels were mapped using Ground penetrating radar (GPR), showing that Tellbreen has a diverse drainage system that is capable of storing, transporting and releasing water year round. In the upper part of the glacier, drainage is mainly via supraglacial channels. These transition downglacier into shallow englacial "cut and closure" channels, formed by the incision and closure of supraglacial channels. Below thin ice near the terminus, these channels reach the bed and contain stored water throughout the winter months. Even though the bed is below pressure-melting point, Tellbreen has a surface-fed, channelized subglacial drainage system, which allows significant storage and delayed discharge.

scholarly journals Thermal structure and drainage system of a small valley glacier (Tellbreen, Svalbard), investigated by ground penetrating radar

2011 ◽  
Vol 5 (1) ◽  
pp. 139-149 ◽  
Author(s):  
K. Bælum ◽  
D. I. Benn
Keyword(s):  
Ground Penetrating Radar ◽  
Thermal Structure ◽  
Drainage System ◽  
High Arctic ◽  
Differential Gps ◽  
Glacier Surface ◽  
Digital Elevation ◽  
Drainage Channels ◽  
Ground Penetrating ◽  
Subglacial Drainage

Abstract. Proglacial icings accumulate in front of many High Arctic glaciers during the winter months, as water escapes from englacial or subglacial storage. Such icings have been interpreted as evidence for warm-based subglacial conditions, but several are now known to occur in front of cold-based glaciers. In this study, we investigate the drainage system of Tellbreen, a 3.5 km long glacier in central Spitsbergen, where a large proglacial icing develops each winter, to determine the location and geometry of storage elements. Digital elevation models (DEMs) of the glacier surface and bed were constructed using maps, differential GPS and ground penetrating radar (GPR). Rates of surface lowering indicate that the glacier has a long-term mass balance of −0.6 ± 0.2 m/year. Englacial and subglacial drainage channels were mapped using GPR, showing that Tellbreen has a diverse drainage system that is capable of storing, transporting and releasing water year round. In the upper part of the glacier, drainage is mainly via supraglacial channels. These transition downglacier into shallow englacial "cut and closure" channels, formed by the incision and roof closure of supraglacial channels. Below thin ice near the terminus, these channels reach the bed and contain stored water throughout the winter months. Even though no signs of temperate ice were detected and the bed is below pressure-melting point, Tellbreen has a surface-fed, channelized subglacial drainage system, which allows significant storage and delayed discharge.

scholarly journals Repeated ground-penetrating radar measurements to detect seasonal and annual variations of an englacial conduit network

2020 ◽  
Author(s):  
Gregory Church ◽  
Andreas Bauder ◽  
Melchior Grab ◽  
Cédric Schmelzbach ◽  
Hansruedi Maurer
Keyword(s):  
Ground Penetrating Radar ◽  
Winter Season ◽  
Drainage System ◽  
Reflection Coefficients ◽  
Drainage Systems ◽  
Impedance Inversion ◽  
Ground Penetrating ◽  
Conduit Network ◽  
Subglacial Drainage ◽  
Englacial Drainage

<p>Surface meltwater is routed through the glacier’s interior by englacial drainage systems into the subglacial drainage system. The subglacial drainage system plays an important control on the glacier sliding velocity. Therefore, studying the evolution of englacial drainage systems throughout the melt season is key to understanding how these englacial drainage systems develop, and how they subsequently feed the subglacial drainage system.</p><p>We have conducted 10 repeated ground-penetrating radar using a Sensor & Software pulseEKKO Pro GPR system with 25 MHz antenna between 2012 and 2019 over an englacial conduit network, 90 m below the glacier’s surface, on the Rhonegletscher, Switzerland. These repeated measurements allowed insights into both annual and seasonal changes. We were also able to have direct observations into the englacial conduit network from six boreholes that were drilled in August 2018 using a GeoVISION<sup>TM</sup> Dual-Scan borehole camera.</p><p>The annual results provided evidence that the englacial drainage network developed between 2012 and 2017. The seasonal evolution of the englacial conduit was studied by inverting the GPR data using an impedance inversion. The impedance inversion delivered reflection coefficients, which provides information on the englacial material properties associated with the englacial conduits. The inversion results provide evidence that during the winter season the englacial network is inactive. During June the englacial network becomes active by transporting surface melt water, and it becomes fully active later in the melt season (August). The reflectivity in summer (June-October) is -0.6, indicating the presence of water within the network. In winter (November-May) the reflectivity is around 0 indicating that the system is neither air or water filled and therefore the system physically closes.</p><p>The data processing workflow provided a top and bottom reflection coefficient of the conduit. The travel time between the reflection coefficients can be converted to a thickness when using EM wave velocity of water (from 2018 borehole observations). During the summer months the englacial network is around a quarter wavelength thick (0.3 m), which is approximately the limit of the vertical resolution.</p>

scholarly journals Monitoring the seasonal changes of an englacial conduit network using repeated ground-penetrating radar measurements

2020 ◽  
Vol 14 (10) ◽  
pp. 3269-3286 ◽  
Author(s):  
Gregory Church ◽  
Melchior Grab ◽  
Cédric Schmelzbach ◽  
Andreas Bauder ◽  
Hansruedi Maurer
Keyword(s):  
Ground Penetrating Radar ◽  
Drainage System ◽  
Reflection Coefficients ◽  
System A ◽  
Impedance Inversion ◽  
Waveform Modelling ◽  
Infill Material ◽  
Ground Penetrating ◽  
Conduit Network ◽  
Subglacial Drainage

Abstract. Englacial conduits act as water pathways to feed surface meltwater into the subglacial drainage system. A change of meltwater into the subglacial drainage system can alter the glacier's dynamics. Between 2012 and 2019, repeated 25 MHz ground-penetrating radar (GPR) surveys were carried out over an active englacial conduit network within the ablation area of the temperate Rhonegletscher, Switzerland. In 2012, 2016, and 2017 GPR measurements were carried out only once a year, and an englacial conduit was detected in 2017. In 2018 and 2019 the repetition survey rate was increased to monitor seasonal variations in the detected englacial conduit. The resulting GPR data were processed using an impedance inversion workflow to compute GPR reflection coefficients and layer impedances, which are indicative of the conduit's infill material. The spatial and temporal evolution of the reflection coefficients also provided insights into the morphology of the Rhonegletscher's englacial conduit network. During the summer melt seasons, we observed an active, water-filled, sediment-transporting englacial conduit network that yielded large negative GPR reflection coefficients (<-0.2). The GPR surveys conducted during the summer provided evidence that the englacial conduit was 15–20 m±6 m wide, ∼0.4m±0.35m thick, ∼250m±6m long with a shallow inclination (2∘), and having a sinusoidal shape from the GPR data. We speculate that extensional hydraulic fracturing is responsible for the formation of the conduit as a result of the conduit network geometry observed and from borehole observations. Synthetic GPR waveform modelling using a thin water-filled conduit showed that a conduit thickness larger than 0.4 m (0.3× minimum wavelength) thick can be correctly identified using 25 MHz GPR data. During the winter periods, the englacial conduit no longer transports water and either physically closed or became very thin (<0.1 m), thereby producing small negative reflection coefficients that are caused by either sediments lying within the closed conduit or water within the very thin conduit. Furthermore, the englacial conduit reactivated during the following melt season at an identical position as in the previous year.

scholarly journals Sources of backscatter at 5.3 GHz from a superimposed ice and firn area revealed by multi-frequency GPR and cores

2009 ◽  
Vol 55 (190) ◽  
pp. 373-383 ◽  
Author(s):  
Kirsty Langley ◽  
Pascal Lacroix ◽  
Svein-Erik Hamran ◽  
Ola Brandt
Keyword(s):  
Ground Penetrating Radar ◽  
Continuous Wave ◽  
Wave System ◽  
Air Bubble ◽  
Radar Systems ◽  
Impulse System ◽  
Polythermal Glacier ◽  
Bubble Number ◽  
Ground Penetrating ◽  
Previous Summer

AbstractWe investigate the major sources of backscatter at 5.3 GHz, within the superimposed ice and firn areas of a polythermal glacier. Two ground-penetrating radar systems, an 800 MHz impulse system and a polarimetric 5.3 GHz frequency-modulated continuous-wave system, are used to acquire along-glacier profiles in the accumulation area of Kongsvegen, Svalbard. The 800 MHz response is used to map reflection horizons in the glacier. Using cores from the superimposed ice and firn areas, the causes of these reflection horizons, in terms of snow, firn and ice layers, are investigated. Superimposing the reflection horizons on the co-polarized and cross-polarized 5.3 GHz profile, we are able to determine how the 5.3 GHz frequency responds to the different media. Scattering at rough interfaces and volume scattering occur in the superimposed ice area and are apparently caused by air-bubble number, size and distribution. In the firn the strongest return originates from below the previous summer surface, consistent with previous findings. At approximately the same depth, strong incoherent scattering begins. The rapid decrease in coherent reflections indicates the significance of scattering in the firn.

scholarly journals Detection of Underground Anomalies Using Analysis of Ground Penetrating Radar Attribute

2020 ◽  
Vol 1 (1) ◽  
Author(s):  
Cuong Van Anh LE ◽  
Thuan Van NGUYEN
Keyword(s):  
Ground Penetrating Radar ◽  
Urban Areas ◽  
Geophysical Methods ◽  
Synthetic Data ◽  
Drainage System ◽  
Real Data ◽  
Building Structures ◽  
Water Drainage ◽  
Diffraction Curve ◽  
Ground Penetrating

Need of specifying underground construction works for supporting further tasks as maintenance, repairing, or setting up new underground structures. For these needs, ground penetrating radar, one of the efficient geophysical methods, can bring high-resolution and quick underground image revealing existence of both natural and artificial anomalies. Its fixed receiver-transmitter antennas setting as constant offset is commonly used in urban areas. Conventionally, hyperbolae events are crucial indicator for scattering objects as kinds of pipes, water drainage system, and concrete building structures as well as sink holes. Calculation of their depths and sizes requires migration analysis with the environment velocity. Migrated sections with different velocity show different chaos degrees of transformation from a hyperbola diffraction curve to its focused area. We have researched diagrams of different Ground Penetrating Radar attributes as energy, entropy, and varimax dependent on two variables, velocity and window zone covering diffraction events from a set of synthetic data and real data, in specifying the environment velocity. We have developed a novel technique for evaluation of the ground velocity and object’s size by combination of the new varimax diagram and the Kirchhoff migration method. The technique can define contribution of diffracted ground penetrating radar waves for building the diagram after removing the reflection contribution. The synthetic datasets consist of different random background noise levels and expressions of different-sized circular and rectangular pipes. The real data is measured for detecting two underground gas pipes in Ba Ria – Vung Tau province, Vietnam.

scholarly journals High-resolution hydrothermal structure of Hansbreen, Spitsbergen, mapped by ground-penetrating radar

1999 ◽  
Vol 45 (151) ◽  
pp. 524-532 ◽  
Author(s):  
J.C. Moore ◽  
A. Pälli ◽  
F. Ludwig ◽  
H. Blatter ◽  
J. Jania ◽  
...  
Keyword(s):  
High Resolution ◽  
Ground Penetrating Radar ◽  
Water Levels ◽  
Large Water ◽  
Complex Temperature ◽  
Polythermal Glacier ◽  
Ground Penetrating ◽  
Isolated Point ◽  
Radar Wave ◽  
Water Contents

AbstractDetailed ground-penetrating radar (GPR) surveys at 50 and 200 MHz on Hansbreen, a polythermal glacier in southern Svalbard, are presented and interpreted. Comparison of the variations in character of the radar reflections with borehole thermometry and water levels in moulins suggests that GPR can be used to study the hydrothermal properties of the glacier. The high resolution of the GPR data shows that the hydrothermal structure of the glacier is highly variable both along the centre line and on transverse profiles. Water contents for many places and depths within the glacier were calculated by estimating radar-wave velocities to point reflectors. We find typical water contents of 1-2% for the temperate ice, but wetter ice associated with surface crevassing and moulins (typically 4% water content). There is evidence that wet ice sometimes overlays drier ice. The hydrothermal structure is thus shown to be very complex. Temperature gradients in the cold ice indicate freezing rates of temperate ice below cold ice of 0.1-0.5 ma-1, while isolated point reflectors within the cold ice indicate large water-filled bodies that are probably related to the regular drainage structure of the glacier.

scholarly journals Subglacial chemical erosion: seasonal variations in solute provenance, Haut Glacier D’Arolla, Valais, Switzerland

1996 ◽  
Vol 22 ◽  
pp. 25-31 ◽  
Author(s):  
G. H. Brown ◽  
M. Sharp ◽  
M. Tranter
Keyword(s):  
Seasonal Variations ◽  
Chemical Weathering ◽  
Drainage System ◽  
Sea Salt ◽  
Major Conclusion ◽  
Chemical Erosion ◽  
Dissolved Species ◽  
Aerosol Dissolution ◽  
Weathering Process ◽  
Subglacial Drainage

This paper determines the provenance of solute in bulk meltwaters draining Haut Glacier d’Arolla, Valais, Switzerland, during the 1989 ablation season. Dissolved species are partitioned into components derived from sea salt, acid aerosol, dissolution of atmospheric CO2, and lithogenic sources, namely carbonates, sulphides and aluminosillicates. A major conclusion is that trace geochemically reactive minerals in the bedrock contribute the bulk of the solute found in runoff. Seasonal changes in solute provenance and in the dominant chemical weathering process are observed. Whereas the chemical weathering of aluminosillicate minerals by carbonation reactions remains relatively constant during the ablation season, the chemical erosion of carbonates shows distinct seasonal variations, reflecting changes in the nature of the subglacial drainage system. Subglacial drainage structure and bedrock type are key controls on the extent of subglacial chemical weathering.

Evolution of chemical weathering processes and CO2 sequestration in the glaciated basins of Western Himalayas

2021 ◽  
Author(s):  
Kalyan biswal ◽  
Naveen kumar ◽  
Mohd soheb ◽  
Ramanathan al
Keyword(s):  
Chemical Weathering ◽  
Arid Zone ◽  
Drainage System ◽  
Molar Ratio ◽  
Crustal Rock ◽  
Carbonate Dissolution ◽  
Western Himalayas ◽  
Rock Types ◽  
Sequestration Rate ◽  
Specific Discharge

&lt;p&gt;Understanding of chemical weathering process involved in ionic elution helps in distinguishing the CO&lt;sub&gt;2&lt;/sub&gt; sequestration rate at the different micro-climatic setup of Himalayan catchments. In the present study, we have selected three glaciated basins from two different climatic zones of Western Himalayas (Lato and Phutse from the cold-arid zone of Ladakh and Chhota Shigri from the monsoon-arid zone of Himachal Pradesh, India) for determining various solute sources, CO&lt;sub&gt;2&lt;/sub&gt; sequestration rate and its control over melt-water quality. Solute sourcing models used in this work shows major cations like Ca&lt;sup&gt;2+&lt;/sup&gt;&amp;#160; and Mg&lt;sup&gt;2+ &lt;/sup&gt;are from crustal rock-weathering while Na&lt;sup&gt;+&lt;/sup&gt; and K&lt;sup&gt;+&lt;/sup&gt; sourced out from the sea-salt origin. However, major anions like SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2-&lt;/sup&gt; (&gt; 85%) were derived from the crustal origin and HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; mostly derived from atmospheric sources (39% to 45 %) in all catchments except HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; contribution from carbonation dissolution and silicate weathering is ~29% and ~16% for Ladakh catchments compared to ~9 % and ~29% in Chhota Shigri respectively. The solute model also reveals that the contribution of sulphate oxidative mediated carbonate dissolution (SOCD) in HCO&lt;sub&gt;3&lt;/sub&gt;&lt;sup&gt;-&lt;/sup&gt; flux is relatively higher in Chhota Shigri (~16%) than others (~9%). It is also observed that catchment like Chhota Shigri having a combined network of channelized and distributed drainage patterns with lower specific discharge, more glacierized area, low pH, high pCO&lt;sub&gt;2&lt;/sub&gt;, Low molar ratio [Ca&lt;sup&gt;2+&lt;/sup&gt; + Mg&lt;sup&gt;2+&lt;/sup&gt;]/[ Na&lt;sup&gt;+&lt;/sup&gt; + K&lt;sup&gt;+&lt;/sup&gt;], high SMF (~ 0.4), low CO&lt;sub&gt;2 carbonate&lt;/sub&gt;/CO&lt;sub&gt;2 silicate&lt;/sub&gt; ratio (~1.3) show relatively more sulphide oxidative and silicate weathered products than other catchments. Conversely, presence of excess non-glaciated areas in Stok and Phutse having well-channelized subsurface discharge with high CO&lt;sub&gt;2 carbonate&lt;/sub&gt;/CO&lt;sub&gt;2 silicate &lt;/sub&gt;ratio (~10 to ~5) show enhanced carbonation via atmospheric CO&lt;sub&gt;2&lt;/sub&gt; (CAC) and carbonate dissolution with high annual CO&lt;sub&gt;2&lt;/sub&gt; sequestration. Thus, varying subglacial drainage system, specific discharge pattern and reactive rock-types with distinct hydro-micro-climatic set up alters the chemical weathering mechanism in these catchments and control meltwater quality.&lt;/p&gt;

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