Subglacial Constructions and Investigations At Bondhusbreen, Norway

1979 ◽  
Vol 23 (89) ◽  
pp. 363-379 ◽  
Author(s):  
B. Wold ◽  
G. Østrem
Keyword(s):  
Drainage System ◽  
Hot Water ◽  
Electric Power Station ◽  
Water Drainage ◽  
Diversion Tunnel ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Ice Cap ◽  
System A ◽  
Tunnel System

Abstract For the construction of a hydro-electric power station in western Norway, a diversion tunnel was made to collect subglacial melt water under an outlet glacier from the Folgefonni ice cap. Many investigations were carried out by glaciologists and engineers before the project could begin, and several unexpected problems arose during the completion of the project. This paper deals with some of the problems and how they were solved. To avoid coarse glacier-carried material from being flushed into the water-collecting tunnel system, a large sedimentation chamber was constructed in the bedrock under the glacier. The dimensions of this huge chamber were decided from sediment-transport studies in the glacier stream and from studies of old bottom deposits in a lake close to the glacier front. Ice-velocity measurements were made on the glacier surface and similar studies were attempted in sub-glacial ice caves made by spraying hot water near the glacier bed, where the ice is 170 m thick. The subglacial water-drainage system was studied from a horizontal tunnel constructed in the bedrock under the glacier. Some preliminary conclusions are drawn from these studies. In future, it will still be possible to undertake subglacial studies because inspection tunnels have been left in the bedrock, and the accessibility is relatively good.

scholarly journals Subglacial Constructions and Investigations At Bondhusbreen, Norway

1979 ◽  
Vol 23 (89) ◽  
pp. 363-379 ◽  
Author(s):  
B. Wold ◽  
G. Østrem
Keyword(s):  
Drainage System ◽  
Hot Water ◽  
Electric Power Station ◽  
Water Drainage ◽  
Diversion Tunnel ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Ice Cap ◽  
System A ◽  
Tunnel System

AbstractFor the construction of a hydro-electric power station in western Norway, a diversion tunnel was made to collect subglacial melt water under an outlet glacier from the Folgefonni ice cap. Many investigations were carried out by glaciologists and engineers before the project could begin, and several unexpected problems arose during the completion of the project. This paper deals with some of the problems and how they were solved.To avoid coarse glacier-carried material from being flushed into the water-collecting tunnel system, a large sedimentation chamber was constructed in the bedrock under the glacier. The dimensions of this huge chamber were decided from sediment-transport studies in the glacier stream and from studies of old bottom deposits in a lake close to the glacier front.Ice-velocity measurements were made on the glacier surface and similar studies were attempted in sub-glacial ice caves made by spraying hot water near the glacier bed, where the ice is 170 m thick.The subglacial water-drainage system was studied from a horizontal tunnel constructed in the bedrock under the glacier. Some preliminary conclusions are drawn from these studies.In future, it will still be possible to undertake subglacial studies because inspection tunnels have been left in the bedrock, and the accessibility is relatively good.

scholarly journals The use of salt injection and conductivity monitoring to infer near-margin hydrological conditions on Vestari-Hagafellsjökull, Iceland

2005 ◽  
Vol 40 ◽  
pp. 83-88 ◽  
Author(s):  
Natalie S. Eyre ◽  
Antony J. Payne ◽  
Duncan J. Baldwin ◽  
Helgi Björnsson
Keyword(s):  
Large Fraction ◽  
Drainage System ◽  
Water Source ◽  
Hot Water ◽  
Outlet Glacier ◽  
Near Surface ◽  
Ice Cap ◽  
Water Head ◽  
A New Technique ◽  
Subglacial Drainage

AbstractVestari-Hagafellsjökull is a surge-type outlet glacier from the Langjökull ice cap, Iceland. Intensive hydrological investigations were carried out during non-surge conditions in the summers of 1999 and 2000, and 14 boreholes were drilled using pressurized hot water over an area 800 m from the margin and approximately 5000 m2 in size, where ice thickness ranged from 60 to 70 m. Initial investigations showed that a large fraction of the boreholes drilled to the bed did not drain and were assumed not to connect to the subglacial drainage system. Subsequently, we investigated the hypothesis that boreholes which remain full may do so as a consequence of a balance between englacial inflow and basal drainage rather than the standard assumption that such boreholes are simply unconnected. In testing this hypothesis, we developed a new technique for measuring water motion within the borehole by monitoring the passage of a saline solution down the borehole’s water column. The technique allows rates of motion to be established, as well as allowing the quantification of net addition and loss of water from the borehole. Observations based on the motion of saline plumes within the boreholes lead us to the conclusion that some boreholes do indeed remain full as a consequence of a balance between englacial inflow and subglacial drainage. The abrupt dilution that occurs at the top of these boreholes suggests inflow from a near-surface englacial water source, while the descent of the saline plumes implies that water is being lost at the base to the subglacial system. The system appears to be driven by excess water head in the boreholes over flotation and implies that the borehole/bedrock interface can be ‘leaky’.

scholarly journals Impact of dust deposition on the albedo of Vatnajökull ice cap, Iceland

2017 ◽  
Vol 11 (2) ◽  
pp. 741-754 ◽  
Author(s):  
Monika Wittmann ◽  
Christine Dorothea Groot Zwaaftink ◽  
Louise Steffensen Schmidt ◽  
Sverrir Guðmundsson ◽  
Finnur Pálsson ◽  
...  
Keyword(s):  
Mass Balance ◽  
Radiative Forcing ◽  
Climate Model ◽  
Dispersion Model ◽  
Dust Deposition ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Ice Cap ◽  
Weather Stations ◽  
Dust Events

Abstract. Deposition of small amounts of airborne dust on glaciers causes positive radiative forcing and enhanced melting due to the reduction of surface albedo. To study the effects of dust deposition on the mass balance of Brúarjökull, an outlet glacier of the largest ice cap in Iceland, Vatnajökull, a study of dust deposition events in the year 2012 was carried out. The dust-mobilisation module FLEXDUST was used to calculate spatio-temporally resolved dust emissions from Iceland and the dispersion model FLEXPART was used to simulate atmospheric dust dispersion and deposition. We used albedo measurements at two automatic weather stations on Brúarjökull to evaluate the dust impacts. Both stations are situated in the accumulation area of the glacier, but the lower station is close to the equilibrium line. For this site ( ∼  1210 m a.s.l.), the dispersion model produced 10 major dust deposition events and a total annual deposition of 20.5 g m−2. At the station located higher on the glacier ( ∼  1525 m a.s.l.), the model produced nine dust events, with one single event causing  ∼  5 g m−2 of dust deposition and a total deposition of  ∼  10 g m−2 yr−1. The main dust source was found to be the Dyngjusandur floodplain north of Vatnajökull; northerly winds prevailed 80 % of the time at the lower station when dust events occurred. In all of the simulated dust events, a corresponding albedo drop was observed at the weather stations. The influence of the dust on the albedo was estimated using the regional climate model HIRHAM5 to simulate the albedo of a clean glacier surface without dust. By comparing the measured albedo to the modelled albedo, we determine the influence of dust events on the snow albedo and the surface energy balance. We estimate that the dust deposition caused an additional 1.1 m w.e. (water equivalent) of snowmelt (or 42 % of the 2.8 m w.e. total melt) compared to a hypothetical clean glacier surface at the lower station, and 0.6 m w.e. more melt (or 38 % of the 1.6 m w.e. melt in total) at the station located further upglacier. Our findings show that dust has a strong influence on the mass balance of glaciers in Iceland.

scholarly journals Applied Glacier Research for Planning Hydro-Electric Power, Ilulissat/Jakobshavn, West Greenland

1989 ◽  
Vol 13 ◽  
pp. 257-261 ◽  
Author(s):  
H.H. Thomsen ◽  
L. Thorning ◽  
O.B. Olesen
Keyword(s):  
Electric Power ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Hot Water ◽  
Electric Power Station ◽  
Water Drainage ◽  
Drainage Pattern ◽  
Drainage Basins ◽  
Model Calculations ◽  
Radio Echo Sounding

Glaciological investigations were carried out on the Greenland ice sheet to help develop plans for a hydro-electric power station to supply energy to Ilulissat/Jakobshavn. The investigations required research on supraglacial and subglacial melt-water drainage in order to delineate water-drainage basins. This involved repeated detailed photogrammetric mapping, radio echo-sounding, hot-water drilling, and mathematical modelling of subglacial drainage. Repeated mappings combine to show an overall stability in the supraglacial drainage pattern, while model calculations for the subglacial conditions show a limited sensitivity in the predicted drainage areas to changes in hydraulic conditions. The investigations provide the basis for setting safer limits for planning hydro-electric power in the area, and give a general understanding of glacier hydrology for a continuous ice cover such as the Greenland ice sheet.

scholarly journals Ground-water intrusions in a mine beneath Høganesbreen, Svalbard: assessing the possibility of evacuating water subglacially

2003 ◽  
Vol 37 ◽  
pp. 269-274 ◽  
Author(s):  
Kjetil Melvold ◽  
Thomas Schuler ◽  
Gaute Lappegard
Keyword(s):  
Ground Water ◽  
Drainage System ◽  
Hot Water ◽  
Measured Temperature ◽  
System A ◽  
Basal Ice ◽  
Global Positioning ◽  
Pressure Melting ◽  
Ground Penetrating ◽  
The Given

AbstractEvacuation of the ground-water intruding into a coal mine beneath Høganesbreen, Svalbard, is difficult and expensive. To solve this problem, it was proposed that the mine be connected to the ice–bedrock interface. Pumping hot water from the mine should establish a flow path along the glacier bed where the ground-water would drain gravitationally. In this paper, we assess the requirements for maintaining such a drainage system in open-channel conditions. To obtain the bedrock topography, we determined the ice thickness by ground-penetrating radar and subtracted it from the surface elevation measured by global positioning system. A measured temperature profile at the site where the mine should connect to the glacier bed (140m depth) revealed that the basal ice is below the pressure-melting point. The locations of major subglacial conduits were estimated using a hydraulic-potential approach. We adopted a model oftime-dependent discharge through a Röthlisberger channel to calculate a set of scenarios using different flow-law parameters. Results of the simulations suggest that for the given conditions, water flow would be pressurized, thereby inhibiting the gravitational drainage of the mine.

scholarly journals Glaciological observations of Brúarjökull, Iceland, using synthetic aperture radar and thematic mapper satellite data

1995 ◽  
Vol 21 ◽  
pp. 271-276 ◽  
Author(s):  
Dorothy K. Hall ◽  
Richard S. Williams ◽  
Oddur Sigurdsson
Keyword(s):  
Synthetic Aperture Radar ◽  
Thematic Mapper ◽  
Synthetic Aperture ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Near Surface ◽  
Ice Cap ◽  
Scatter Coefficient ◽  
History Of ◽  
Aperture Radar

The first European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) images offer opportunities for studying glacier surface properties and near-surface features. Analysis of back-scatter values from digital SAR data from 18 January, 7 June, 1 September and 25 October 1993 of Brúarjökull, an outlet glacier on the northeastern margin of the Vatnajökull ice cap, Iceland, that has a history of episodic surges, reveals several back-scatter boundaries that may relate to glacier facies and, inferentially, to mass balance. For example, a strong back-scatter boundary on the 18 January image of the snow-covered glacier, representing a back-scatter coefficient, σ°, difference of 4.34dB, appears to coincide with the position of the transient snow line at the end of the 1990–91 budget year. The boundary is visible on the 7 September 1991 Landsat thematic mapper (TM) image. The terminus is very difficult to define because of back-wasting from the last surge (1963–64) but is most easily delineated on the 1 September 1993 SAR and the 7 September 1991 TM images, in part due to the presence of ice-margin lakes.

scholarly journals Automated detection of basal icequakes and discrimination from surface crevassing

2019 ◽  
Vol 60 (79) ◽  
pp. 167-181 ◽  
Author(s):  
Thomas S. Hudson ◽  
Jonathan Smith ◽  
Alex M. Brisbourne ◽  
Robert S. White
Keyword(s):  
Seismic Energy ◽  
Automated Detection ◽  
Ice Streams ◽  
Glacier Surface ◽  
Ice Dynamics ◽  
Outlet Glacier ◽  
Ice Cap ◽  
Basal Sliding ◽  
Dynamics Models ◽  
Critical Process

ABSTRACTIcequakes at or near the bed of a glacier have the potential to allow us to investigate the interaction of ice with the underlying till or bedrock. Understanding this interaction is important for studying basal sliding of glaciers and ice streams, a critical process in ice dynamics models used to constrain future sea-level rise projections. However, seismic observations on glaciers can be dominated by seismic energy from surface crevassing. We present a method of automatically detecting basal icequakes and discriminating them from surface crevassing, comparing this method to a commonly used spectrum-based method of detecting icequakes. We use data from Skeidararjökull, an outlet glacier of the Vatnajökull Ice Cap, South-East Iceland, to demonstrate that our method outperforms the commonly used spectrum-based method. Our method detects a higher number of basal icequakes, has a lower rate of incorrectly identifying crevassing as basal icequakes and detects an additional, spatially independent basal icequake cluster. We also show independently that the icequakes do not originate from near the glacier surface. We conclude that the method described here is more effective than currently implemented methods for detecting and discriminating basal icequakes from surface crevassing.

scholarly journals Analyses of a surging outlet glacier of Vatnajökull ice cap, Iceland

2005 ◽  
Vol 42 ◽  
pp. 23-28 ◽  
Author(s):  
Guðfinna Aðalgeirsdóttir ◽  
Helgi Björnsson ◽  
Finnur Pálsson ◽  
Eyjolfur Magnússon
Keyword(s):  
Mass Balance ◽  
Glacier Surface ◽  
Measured Velocity ◽  
Outlet Glacier ◽  
Ice Cap ◽  
Elevation Changes ◽  
History Of ◽  
Northern Side ◽  
The Difference ◽  
Approximation Type

AbstractMany of the large outlet glaciers of Vatnajökull ice cap, Iceland, have a history of regular surges. The mass transport during surges can be up to 25% of the total ice flux. This is a considerable amount that affects the whole ice cap, the location of the ice divides, the flow field and the size and shape of the ice cap. Data from the surging outlet Dyngjujökull, on the northern side of Vatnajökull, which surged during the period 1998-2000, are presented: surface elevation changes, displacement and total mass tr ansport. The total gain in ice volume in the receiving area, due to the surge, is considerably smaller than the loss in the reservoir area. The difference is mainly due to enhanced melting rates on the larger surface area of the crevassed glacier surface, and increased turbulent fluxes above the surface, but also due to increased frictional melting at the bed during the surge. A two-dimensional vertically integrated numerical flow model, of standard shallow-ice approximation type, is used to show that a modeled glacier that is similar in size to Dyngjujökull and subject to the same mass balance has three times higher velocities than the measured velocity during the quiescent phase. Adding surges in the numerical model, by periodically increasing the sliding velocity, causes the glacier to retreat and oscillate around a smaller state when subject to the same mass-balance regime. Lowering the equilibrium line by 50 m lets the modeled surging glacier oscillate around a size similar to that of the present glacier, indicating that surging is an efficient long-term ablation mechanism.

Drainage Basins on Vatnajökull Mapped by Radio Echo Soundings

1982 ◽  
Vol 13 (4) ◽  
pp. 213-232 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Drainage Basin ◽  
Water Drainage ◽  
Drainage Basins ◽  
Glacier Surface ◽  
Ice Cap ◽  
Ice Surface ◽  
Surface Maps

Maps are presented for the glacier surface and the bedrock of two areas on Vatnajökull - Tungnárjökull and Sylgjujökull in the western ice cap and Eyjabakkajökull in the northeast. The ice surface maps are obtained by precision barometric altimeter. They form the basis for delimitation of ice drainage basins. The bedrock maps are the results of radio echo soundings. Both maps are used for defining the water drainage basin which is estimated 121 km2 for the river Tungná, 85 km2 for the rivers from Sylgjujökull and 117 km2 for the rivers from Eyjabakkajökull.

scholarly journals Structural controls on englacial esker sedimentation: Skeiðarárjökull, Iceland

2009 ◽  
Vol 50 (51) ◽  
pp. 85-92 ◽  
Author(s):  
Matthew J. Burke ◽  
John Woodward ◽  
Andrew J. Russell ◽  
P. Jay Fleisher
Keyword(s):  
Structural Control ◽  
Preferential Flow ◽  
High Amplitude ◽  
Glacier Surface ◽  
Outlet Glacier ◽  
Structural Controls ◽  
Ice Cap ◽  
Accommodation Space ◽  
Glacier Ice ◽  
Ground Penetrating

AbstractWe have used ground-penetrating radar (GPR) to observe englacial structural control upon the development of an esker formed during a high-magnitude outburst flood (jökulhlaup). The surge-type Skeiðarárjökull, an outlet glacier of the Vatnajökull ice cap, Iceland, is a frequent source of jökulhlaups. The rising-stage waters of the November 1996 jökulhlaup travelled through a dense network of interconnected fractures that perforated the margin of the glacier. Subsequent discharge focused upon a small number of conduit outlets. Recent ice-marginal retreat has exposed a large englacial esker associated with one of these outlets. We investigated structural controls on esker genesis in April 2006, by collecting >2.5km of GPR profiles on the glacier surface up-glacier of where the esker ridge has been exposed by meltout. In lines closest to the exposed esker ridge, we interpret areas of englacial horizons up to ~30m wide and ~10–15m high as an up-glacier continuation of the esker sediments. High-amplitude, dipping horizons define the base of esker materials across many lines. Similar dipping surfaces deeper in the profiles suggest that: (1) the dipping surfaces beneath the esker are englacial tephera bands; (2) floodwaters were initially discharged along structurally controlled englacial surfaces (tephra bands); (3) the rapid increase in discharge resulted in hydrofracturing; (4) establishment of preferential flow paths resulted in conduit development along the tephra bands due to localized excavation of surrounding glacier ice; and (5) sedimentation took place within the new accommodation space to form the englacial structure melting out to produce the esker.

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