Cold–temperate transition surface and permafrost base (CTS-PB) as an environmental axis in glacier–permafrost relationship, based on research carried out on the Storglaciären and its forefield, northern Sweden

2017 ◽  
Vol 88 (3) ◽  
pp. 551-569 ◽  
Author(s):  
Wojciech Dobiński ◽  
Mariusz Grabiec ◽  
Michał Glazer
Keyword(s):  
Ground Penetrating Radar ◽  
Cold Climate ◽  
Northern Sweden ◽  
Climatic Fluctuation ◽  
Glacial Ice ◽  
Empirical Ground ◽  
Glacial Environments ◽  
Transition Surface ◽  
Ground Penetrating ◽  
Tomography Data

AbstractHere, we present empirical ground penetrating radar (GPR) and electroresistivity tomography data (ERT) to verify the cold-temperate transition surface-permafrost base (CTS-PB) axis theoretical model. The data were collected from Storglaciären, in Tarfala, Northern Sweden, and its forefield. The GPR results show a material relation between the glacial ice and the sediments incorporated in the glacier, and a geophysical relation between the “cold ice” and the “temperate ice” layers. Clearly identifying lateral glacier margins is difficult, as periglacial and glacial environments frequently overlap. In this case, we identified areas showing permafrost aggradation already under the glacier, particularly where the CTS is replaced by the PB surface. This structure appears as a result of the influence of a cold climate over both the glacial and periglacial environments. The results show how these surfaces form a specific continuous environmental axis; thus, both glacial and periglacial areas can be treated uniformly as a specific continuum in the geophysical sense. Similarly, other examples previously described also allow identifying a continuation of permafrost from the periglacial environment onto the glacial base. In addition, the ERT results show the presence of double-layered periglacial permafrost, possibly suggesting a past climatic fluctuation in the study area.

scholarly journals Assessing Ground Penetrating Radar's Ability to Image Subsurface Characteristics of Icy Debris Fans in Alaska and New Zealand

2018 ◽  
Vol 23 (4) ◽  
pp. 423-436 ◽  
Author(s):  
Robert W. Jacob ◽  
Jeffrey M. Trop ◽  
R. Craig Kochel
Keyword(s):  
New Zealand ◽  
Ground Penetrating Radar ◽  
Transverse Electric ◽  
Transverse Magnetic ◽  
Glacial Ice ◽  
Signal Velocity ◽  
Alpine Regions ◽  
Flow Processes ◽  
Ground Penetrating ◽  
Antenna Polarization

Icy debris fans have recently been described as fan shaped depositional landforms associated with (or formed during) deglaciation, however, the subsurface characteristics remain essentially undocumented. We used ground penetrating radar (GPR) to non-invasively investigate the subsurface characteristics of icy debris fans (IDFs) at McCarthy Glacier, Alaska, USA and at La Perouse Glacier, South Island of New Zealand. IDFs are largely unexplored paraglacial landforms in deglaciating alpine regions at the mouths of bedrock catchments between valley glaciers and icecaps. IDFs receive deposits of mainly ice and minor lithic material through different mass-flow processes, chiefly ice avalanche and to a lesser extent debris flow, slushflow, and rockfall. We report here on the GPR signal velocity observed from 15 different wide-angle reflection/refraction (WARR) soundings on the IDFs and on the McCarthy Glacier; the effect of GPR antenna orientation relative to subsurface reflections; the effect of spreading direction of the WARR soundings relative to topographic contour; observed differences between transverse electric (TE) and transverse magnetic (TM) antenna polarization; and a GPR profile extending from the McCarthy Glacier onto an IDF. Evaluation of the WARR soundings indicates that the IDF deposits have a GPR signal velocity that is similar to the underlying glacier, and that the antenna polarization and orientation did not prevent identification of GPR reflections. The GPR profile on the McCarthy Glacier indicates that the shallowest material is layered, decreases in thickness down fan, and has evidence of brittle failure planes (crevasses). The GPR profile and WARR soundings collected in 2013 indicate that the thickness of the McCarthy Glacier is 82 m in the approximate middle of the cirque and that the IDF deposits transition with depth into flowing glacial ice.

scholarly journals An automatic approach to delineate the cold–temperate transition surface with ground-penetrating radar on polythermal glaciers

2014 ◽  
Vol 55 (67) ◽  
pp. 89-96 ◽  
Author(s):  
Clemens Schannwell ◽  
Tavi Murray ◽  
Bernd Kulessa ◽  
Alessio Gusmeroli ◽  
Albane Saintenoy ◽  
...  
Keyword(s):  
Ground Penetrating Radar ◽  
Thermal Structure ◽  
Gradual Transition ◽  
Signal Power ◽  
Automated Method ◽  
Automatic Picking ◽  
Transition Surface ◽  
The Difference ◽  
Ground Penetrating ◽  
Good Agreement

AbstractGround-penetrating radar has been widely used to map the thermal structure of polythermal glaciers. Hitherto, the cold–temperate transition surface (CTS) in radargrams has been identified by a labour-intensive and subjective manual picking method. We introduce a new automatic approach for picking the CTS that uses the difference in signal power exhibited by the cold and temperate ice layers. We compare our automatically computed CTS depths with manual picks. Our results show very good agreement between the two methods in most areas (r2 > 0.7). RMSEs computed at each trace in two-way travel-time from three test sites range from 14 to 19ns (2.4–3.2 m). The proposed automated method mostly fails in areas showing a rather gradual transition in signal power at the CTS. In some areas, high power originating from non-water sources is misinterpreted by the automatic picking method as ‘temperate ice’.

High resolution of glacial ice stratigraphy: A ground‐penetrating radar study of Pegasus Runway, McMurdo Station, Antarctica

Geophysics ◽  
1996 ◽  
Vol 61 (6) ◽  
pp. 1653-1663 ◽  
Author(s):  
Steven A. Arcone
Keyword(s):  
Ground Penetrating Radar ◽  
High Frequency ◽  
Single Layer ◽  
Ice Shelf ◽  
Glacial Ice ◽  
Ross Ice Shelf ◽  
Mineral Particles ◽  
Structural Weakness ◽  
Ground Penetrating ◽  
Brine Layer

Ground‐penetrating radar (GPR) has been used to detect areas of present or potential structural weakness beneath a 3.2-km snow‐covered ice runway on the Ross Ice Shelf, Antarctica. The bandwidths of the transmitted wavelets were centered near 500 MHz. The data show many horizons up to tens of meters long and occurring to about a 9-m depth, below which a brine intrusion limits penetration. The horizons are interpreted as discrete scatterers because of their diffraction nature and loss of higher frequencies with depth. The presence of porous ice or dispersed water is interpreted from wavelet phase. The water may be associated with apparent deepening and fading of the brine horizon. If the above interpretation is correct, water occurs at depths to 3.5 m and extends as much as 40 m horizontally, which is greater and deeper than known previously. At 3.5 m depth, the water may be adsorbed on mineral particles rather than remain free. Migration of the diffractions with a single‐layer migration scheme shows all horizons above the brine layer to be small dielectric perturbations within the ice. Stacking and Hilbert transformation of the data reveal slight folding along the length of the runway. Loss of high‐frequency amplitude in the wavelets suggests that higher frequency radar might improve resolution only in the top few meters.

REFLECTION COEFFICIENT OF AN ELECTROMAGNETIC WAVE IN CONDUCTIVE MEDIA

2018 ◽  
pp. 100-106
Author(s):  
M. S. Sudakova ◽  
M. L. Vladov ◽  
M. R. Sadurtdinov
Keyword(s):  
Reflection Coefficient ◽  
Ground Penetrating Radar ◽  
Electromagnetic Waves ◽  
Water Contamination ◽  
Survey Design ◽  
Direct And Inverse Problems ◽  
The Difference ◽  
Ground Penetrating ◽  
Ideal Dielectric

Within the ground penetrating radar bandwidth the medium is considered to be an ideal dielectric, which is not always true. Electromagnetic waves reflection coefficient conductivity dependence showed a significant role of the difference in conductivity in reflection strength. It was confirmed by physical modeling. Conductivity of geological media should be taken into account when solving direct and inverse problems, survey design planning, etc. Ground penetrating radar can be used to solve the problem of mapping of halocline or determine water contamination.

Deteksi Bentuk Objek Bawah Tanah Menggunakan Pengolahan Citra B-Scan pada Ground Penetrating Radar (GPR)

2017 ◽  
Vol 3 (1) ◽  
pp. 73-83
Author(s):  
Rahmayati Alindra ◽  
Heroe Wijanto ◽  
Koredianto Usman
Keyword(s):  
Signal Processing ◽  
Ground Penetrating Radar ◽  
Post Processing ◽  
Data Survey ◽  
Ground Penetrating

Ground Penetrating Radar (GPR) adalah salah satu jenis radar yang digunakan untuk menyelidiki kondisi di bawah permukaan tanah tanpa harus menggali dan merusak tanah. Sistem GPR terdiri atas pengirim (transmitter), yaitu antena yang terhubung ke generator sinyal dan bagian penerima (receiver), yaitu antena yang terhubung ke LNA dan ADC yang kemudian terhubung ke unit pengolahan data hasil survey serta display sebagai tampilan output-nya dan post  processing untuk alat bantu mendapatkan informasi mengenai suatu objek. GPR bekerja dengan cara memancarkan gelombang elektromagnetik ke dalam tanah dan menerima sinyal yang dipantulkan oleh objek-objek di bawah permukaan tanah. Sinyal yang diterima kemudian diolah pada bagian signal processing dengan tujuan untuk menghasilkan gambaran kondisi di bawah permukaan tanah yang dapat dengan mudah dibaca dan diinterpretasikan oleh user. Signal processing sendiri terdiri dari beberapa tahap yaitu A-Scan yang meliputi perbaikan sinyal dan pendektesian objek satu dimensi, B-Scan untuk pemrosesan data dua dimensi  dan C-Scan untuk pemrosesan data tiga dimensi. Metode yang digunakan pada pemrosesan B-Scan salah satunya adalah dengan  teknik pemrosesan citra. Dengan pemrosesan citra, data survey B-scan diolah untuk didapatkan informasi mengenai objek. Pada penelitian ini, diterapkan teori gradien garis pada pemrosesan citra B-scan untuk menentukan bentuk dua dimensi dari objek bawah tanah yaitu persegi, segitiga atau lingkaran. 

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