scholarly journals Englacial hydrology of Annette Plateau, a temperate alpine glacier, Southern Alps, New Zealand

2021 ◽  
Author(s):  
◽  
Kolja Schaller
Keyword(s):  
Water Table ◽  
Ground Penetrating Radar ◽  
Ice Core ◽  
Radar Data ◽  
Early Spring ◽  
Early Summer ◽  
Seasonal Temperature ◽  
Glacier Surface ◽  
Alpine Glacier ◽  
Ground Penetrating

<p>The movement of water through temperate glaciers is important for understanding fundamental issues within glaciology. These include glacier induced floods, glacier dynamics and run-off prediction. Traditional englacial hydrology is thought to consist of interconnected tubular channels that merge down-glacier and drain through the glacier to the bed. However, englacial hydrology is much debated as the links between the glacier surface and bed are not well understood. Ground penetrating radar (GPR) is a geophysical tool that is well suited for studying glaciated areas. Recent ice coring attempts in New Zealand’s temperate alpine glaciers were not successful in coring to bedrock due to the interception of water at depth. This highlights the need for a better understanding of the englacial hydrology of temperate systems. This study investigates the englacial hydrology at Annette Plateau where on three occasions the interception of water has prevented successful coring to the glacier bed. Ground penetrating radar was used to conduct two high-resolution surveys on Annette Plateau in early spring 2011 and early summer 2011. Across-glacier profiles were acquired at 20 m spacing to enable tracking of englacial reflectors between profiles. Models of temperate englacial features were made to aid feature identification within radar profiles. Radar data is compared with density, stratigraphy and chemistry results from the 45 m ice core obtained at Annette Plateau in winter 2009. The early-summer survey indicates an increase in the glacier’s water content compared with the early-spring survey. Englacial reflectors show evidence of (a) spatially continuous englacial conduits, (b) the formation of a water table feature which shallows down glacier, and (c) detailed bedrock topography. Hydropotential surfaces, calculated for the water table and bedrock horizons, show the direction of water flow. Ice core chemistry shows a correlation between the depth of the water table and a significant hiatus indicated by tritium dating. We infer that an extensive water table has formed on an old melt surface where ice from approximately 1930-1991 has been removed. This water table responds to seasonal temperature changes and hydrological inputs.</p>

scholarly journals Englacial hydrology of Annette Plateau, a temperate alpine glacier, Southern Alps, New Zealand

2021 ◽  
Author(s):  
◽  
Kolja Schaller
Keyword(s):  
Water Table ◽  
Ground Penetrating Radar ◽  
Ice Core ◽  
Radar Data ◽  
Early Spring ◽  
Early Summer ◽  
Seasonal Temperature ◽  
Glacier Surface ◽  
Alpine Glacier ◽  
Ground Penetrating

<p>The movement of water through temperate glaciers is important for understanding fundamental issues within glaciology. These include glacier induced floods, glacier dynamics and run-off prediction. Traditional englacial hydrology is thought to consist of interconnected tubular channels that merge down-glacier and drain through the glacier to the bed. However, englacial hydrology is much debated as the links between the glacier surface and bed are not well understood. Ground penetrating radar (GPR) is a geophysical tool that is well suited for studying glaciated areas. Recent ice coring attempts in New Zealand’s temperate alpine glaciers were not successful in coring to bedrock due to the interception of water at depth. This highlights the need for a better understanding of the englacial hydrology of temperate systems. This study investigates the englacial hydrology at Annette Plateau where on three occasions the interception of water has prevented successful coring to the glacier bed. Ground penetrating radar was used to conduct two high-resolution surveys on Annette Plateau in early spring 2011 and early summer 2011. Across-glacier profiles were acquired at 20 m spacing to enable tracking of englacial reflectors between profiles. Models of temperate englacial features were made to aid feature identification within radar profiles. Radar data is compared with density, stratigraphy and chemistry results from the 45 m ice core obtained at Annette Plateau in winter 2009. The early-summer survey indicates an increase in the glacier’s water content compared with the early-spring survey. Englacial reflectors show evidence of (a) spatially continuous englacial conduits, (b) the formation of a water table feature which shallows down glacier, and (c) detailed bedrock topography. Hydropotential surfaces, calculated for the water table and bedrock horizons, show the direction of water flow. Ice core chemistry shows a correlation between the depth of the water table and a significant hiatus indicated by tritium dating. We infer that an extensive water table has formed on an old melt surface where ice from approximately 1930-1991 has been removed. This water table responds to seasonal temperature changes and hydrological inputs.</p>

scholarly journals Characterization of subglacial marginal channels using 3-D analysis of high-density ground-penetrating radar data

2021 ◽  
pp. 1-14
Author(s):  
Pascal E. Egli ◽  
James Irving ◽  
Stuart N. Lane
Keyword(s):  
Ground Penetrating Radar ◽  
Three Dimensional ◽  
Radar Data ◽  
High Density ◽  
Swiss Alps ◽  
Amplitude Analysis ◽  
Glacier Surface ◽  
Alpine Glacier ◽  
Glacier Terminus ◽  
Ground Penetrating

Abstract Studying subglacial drainage networks is important for understanding the potential relationship between channel dynamics and rapid glacier recession as well as the role of subglacial channels in subglacial sediment evacuation. In order to delineate the planform geometry of snout marginal subglacial channels, densely spaced ground-penetrating radar (GPR) measurements at a frequency of ~70 MHz were carried out over the snout marginal zones of two temperate glaciers in the southwestern Swiss Alps, the Haut Glacier d'Arolla and the Glacier d'Otemma. Three-dimensional (3-D) data processing and amplitude analysis of the GPR reflection along the glacier bed was used to map the channels. At the Haut Glacier d'Arolla, two relatively straight channels of several meters in width were identified. The positions of these channels correspond well with the locations of channel outlets at the glacier terminus, as well as with fractures appearing on the glacier surface one month after the GPR data acquisition. The latter are believed to represent the beginning of ice collapse above the subglacial channels. At the Glacier d'Otemma, a major subglacial conduit was detected with similar dimensions to those identified at the Haut Glacier d'Arolla, but greater sinuosity. The position of this channel was confirmed by drone-based imagery acquired after glacier margin collapse. Our results confirm that high-density 3-D GPR surveys can be used to map subglacial channels near temperate alpine glacier margins.

scholarly journals Unlocking annual firn layer water equivalents from ground-penetrating radar data on an Alpine glacier

2015 ◽  
Vol 9 (3) ◽  
pp. 1075-1087 ◽  
Author(s):  
L. Sold ◽  
M. Huss ◽  
A. Eichler ◽  
M. Schwikowski ◽  
M. Hoelzle
Keyword(s):  
Time Series ◽  
Mass Balance ◽  
Ground Penetrating Radar ◽  
Spatial Representation ◽  
Radar Data ◽  
Glacier Mass Balance ◽  
Accumulation Rates ◽  
Alpine Glacier ◽  
Ground Penetrating ◽  
Over Time

Abstract. The spatial representation of accumulation measurements is a major limitation for current glacier mass balance monitoring approaches. Here, we present a method for estimating annual accumulation rates on a temperate Alpine glacier based on the interpretation of internal reflection horizons (IRHs) in helicopter-borne ground-penetrating radar (GPR) data. For each individual GPR measurement, the signal travel time is combined with a simple model for firn densification and refreezing of meltwater. The model is calibrated at locations where GPR repeat measurements are available in two subsequent years and the densification can be tracked over time. Two 10.5 m long firn cores provide a reference for the density and chronology of firn layers. Thereby, IRHs correspond to density maxima, but not exclusively to former summer glacier surfaces. Along GPR profile sections from across the accumulation area we obtain the water equivalent (w.e.) of several annual firn layers. Because deeper IRHs could be tracked over shorter distances, the total length of analysed profile sections varies from 7.3 km for the uppermost accumulation layer (2011) to 0.1 km for the deepest (i.e. oldest) layer (2006). According to model results, refreezing accounts for 10% of the density increase over time and depth, and for 2% of the water equivalent. The strongest limitation to our method is the dependence on layer chronology assumptions. We show that GPR can be used not only to complement existing mass balance monitoring programmes on temperate glaciers but also to retrospectively extend newly initiated time series.

Reconstructing Properties of Subsurface from Ground-Penetrating Radar Data

PIERS Online ◽  
2006 ◽  
Vol 2 (6) ◽  
pp. 567-572
Author(s):  
Hui Zhou ◽  
Dongling Qiu ◽  
Takashi Takenaka
Keyword(s):  
Ground Penetrating Radar ◽  
Radar Data ◽  
Ground Penetrating

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.

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