scholarly journals Development of a subglacial lake monitored with radio-echo sounding: case study from the eastern Skaftá cauldron in the Vatnajökull ice cap, Iceland

2021 ◽  
Vol 15 (8) ◽  
pp. 3731-3749
Author(s):  
Eyjólfur Magnússon ◽  
Finnur Pálsson ◽  
Magnús T. Gudmundsson ◽  
Thórdís Högnadóttir ◽  
Cristian Rossi ◽  
...  
Keyword(s):  
Lake Area ◽  
Subglacial Lake ◽  
Ice Cap ◽  
Lake Volume ◽  
Digital Elevation ◽  
Geothermal Activity ◽  
Radio Echo Sounding ◽  
Water Volumes ◽  
Elevation Model ◽  
Echo Sounding

Abstract. We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the eastern Skaftá cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is a ∼ 3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ∼ 1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a subglacial lake and is released semi-regularly in jökulhlaups. The RES record consists of annual surveys conducted at the beginning of every summer during the period 2014–2020. Comparison of the RES surveys reveals variable lake area (0.5–4.1 km2) and enables traced reflections from the lake roof to be distinguished from bedrock reflections. This allows construction of a digital elevation model (DEM) of the bedrock in the area, further constrained by two borehole measurements at the cauldron centre. It also allows creation of lake thickness maps and an estimate of lake volume at the time of each survey, which we compare with lowering patterns and released water volumes obtained from pre- and post-jökulhlaup surface DEMs. The estimated lake volume was 250 GL (gigalitres = 106 m3) in June 2015, but 320 ± 20 GL drained from the ESC in October 2015. In June 2018, RES profiles revealed a lake volume of 185 GL, while 220 ± 30 GL were released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10 %–20 % uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected.

scholarly journals Development of a subglacial lake monitored with radio-echo sounding: Case study from the Eastern Skaftá Cauldron in the Vatnajökull ice cap, Iceland

2021 ◽  
Author(s):  
Eyjólfur Magnússon ◽  
Finnur Pálsson ◽  
Magnús T. Gudmundsson ◽  
Thórdís Högnadóttir ◽  
Cristian Rossi ◽  
...  
Keyword(s):  
Lake Area ◽  
Ice Cap ◽  
Lake Volume ◽  
Digital Elevation ◽  
Geothermal Activity ◽  
Before And After ◽  
Radio Echo Sounding ◽  
Water Volumes ◽  
Elevation Model ◽  
Echo Sounding

Abstract. We present repeated radio-echo sounding (RES, 5 MHz) on a profile grid over the Eastern Skaftá Cauldron (ESC) in Vatnajökull ice cap, Iceland. The ESC is ~3 km wide and 50–150 m deep ice cauldron created and maintained by subglacial geothermal activity of ~1 GW. Beneath the cauldron and 200–400 m thick ice, water accumulates in a lake and is released semi-regularly in jökulhlaups. The RES record consists of annual surveys with 200–400 m between profiles in early summers of 2014–2020. Comparison of the RES surveys (2D migrated profiles) reveals variable lake area (0.5–4.1 km2) and enables traced reflections from the lake roof to be distinguished from bedrock reflections. This allows construction of a digital elevation model (DEM) of the bedrock in the area, further constrained by two borehole measurements at the cauldron centre. It also allows creation of lake thickness maps and an estimate of lake volume at the time of each survey, which we compare with lowering patterns and released water volumes obtained from surface DEMs obtained before and after jökulhlaups. The estimated lake volume is 250 × 106 m3 in June 2015 but 320 ± 20 × 106 m3 drained from the cauldron in October 2015. In June 2018, RES profiles reveal a lake volume of 185 × 106 m3 while 220 ± 30 × 106 m3 was released in a jökulhlaup in August 2018. Considering the water accumulation over the periods between RES surveys and jökulhlaups, this indicates 10–20 % uncertainty in the RES-derived volumes at times when significant jökulhlaups may be expected.

The development of a subglacial lake monitored with radio echo sounding and comparison with water volumes released during jökulhlaups: Case study from the Eastern Skaftá Cauldron in the Vatnajökull ice cap, Iceland

2020 ◽  
Author(s):  
Eyjolfur Magnusson ◽  
Finnur Pálsson ◽  
Magnús T. Gudmundsson ◽  
Thórdís Högnadóttir ◽  
Christian Rossi ◽  
...  
Keyword(s):  
Minimum Size ◽  
Water Volume ◽  
Potential Hazard ◽  
Volume Estimate ◽  
Lake Volume ◽  
Geothermal Activity ◽  
Before And After ◽  
Radio Echo Sounding ◽  
Water Volumes ◽  
Echo Sounding

<p>We present a 6 year record of repeated radio echo sounding (RES) on a profile grid (200-400 m between profiles) surveyed over the Eastern Skaftá Cauldron (ESC). ESC is an ice cauldron produced and maintained by powerful geothermal activity (~1 GW) at the glacier bed. Beneath the cauldron and 200-400 m of ice, water accumulates in a lake and is regularly released in jökulhlaups. The maximum discharge in the river Skaftá exceeded 3000 m<sup>3</sup> s<sup>-1</sup> in the most recent ones in 2015 and 2018. The record starts in 2014 and consists of annual measurements, obtained in June each year; the last on June 2019. Comparison of the repeated RES profiles (2D migrated) reveals the margin of the lake at different times and enables a classifying of traced reflections into lake and bedrock measurements. The bedrock measurements were obtained with the lake close to its minimum size in 2016, 2017 and 2019 (£~1 km<sup>2</sup> compared to 4.0 km<sup>2</sup> in 2015), hence it is possible to obtain fairly accurate digital elevation model (DEM) of the glacier/lake bed. This DEM is further constrained by two borehole measurements of the lake bed elevation at its centre. The traced lake reflections and comparison with the bedrock DEM enables creation of a lake thickness maps and an estimate of the lake volume for each survey. The lake thickness maps and volumes in June 2015 and 2018 are compared with the surface lowering pattern and water volumes drained in the jökulhlaups in October 2015 and August 2018. The drained water volume was derived by integrating the surface lowering during the jökulhlaups and adding estimated volume of crevasses formed in the events. The lowering in the 2015 jökulhlaup was obtained from TanDEM-X DEMs of September 23<sup>rd</sup> and October 10<sup>th</sup>, shortly before and after the jökulhlaup. The lowering in the 2018 jökulhlaup was derived from dense set of airborne altimetry profiles acquired on August 9<sup>th</sup>, a few days after the jökulhlaup, compared with a DEM in June 2018 (ArcticDEM in July 2017 corrected with dense GNSS profiles in June 2018). The lake volume estimate from the RES data is 240x10<sup>6</sup> m<sup>3</sup> in June 2015 but 320±20x10<sup>6</sup> m<sup>3</sup> drained from the cauldron in October. In June 2018 a relatively dense RES profile grid (~200 m between profiles) reveals a lake volume of 180x10<sup>6</sup> m<sup>3</sup> while 210±30x10<sup>6</sup> m<sup>3</sup> drained from the cauldron in August. This comparison demonstrates the applicability of our survey approach to monitor the water accumulation in the lake and thus better constrain potential hazard in jökulhlaups.</p>

scholarly journals Forty-seven new subglacial lakes in the 0–110° E sector of East Antarctica

2007 ◽  
Vol 53 (181) ◽  
pp. 289-297 ◽  
Author(s):  
Sergey V. Popov ◽  
Valery N. Masolov
Keyword(s):  
Heat Flux ◽  
Scientific Work ◽  
East Antarctica ◽  
Lake Area ◽  
Geothermal Heat ◽  
Subglacial Lake ◽  
Deep Faults ◽  
Radio Echo Sounding ◽  
Subglacial Lakes ◽  
Echo Sounding

AbstractDuring the summer field seasons of 1987–91, studies of central East Antarctica by airborne radio-echo sounding commenced. This scientific work continued in the 1990s in the Vostok Subglacial Lake area and along the traverse route from Mirny, and led to the discovery of 16 new subglacial water cavities in the areas of Domes Fuji and Argus and the Prince Charles Mountains. Twenty-nine subglacial water cavities were revealed in the area near Vostok, along with a feature we believe to be a subglacial river. Two subglacial lakes were discovered along the Mirny–Vostok traverse route. These are located 50 km north of Komsomolskaya station and under Pionerskaya station. We find high geothermal heat flux in the vicinity of the largest of the subglacial lakes, and suggest this may be due to their location over deep faults where additional mantle heat is available.

A 1976 radio echo sounding expedition to the Vatnajökull ice cap, Iceland

Polar Record ◽  
1977 ◽  
Vol 18 (115) ◽  
pp. 375-377 ◽  
Author(s):  
H. Björnsson ◽  
R. L. Ferrari ◽  
K. J. Miller ◽  
G. Owen
Keyword(s):  
Ice Thickness ◽  
First Year ◽  
Detailed Knowledge ◽  
Polar Regions ◽  
Related Data ◽  
Ice Cap ◽  
Geothermal Activity ◽  
Radio Echo Sounding ◽  
Depth Sounding ◽  
Echo Sounding

This brief report describes the first year of a joint Cambridge University—Iceland University two-year project to develop radio echo depth-sounding apparatus suitable for the temperate ice of the Vatnajökull ice cap. There is much interest in obtaining detailed ice thickness measurements for the 8 400 km2 Vatnajökull area, where only limited ice-depth surveys, using bore-hole and seismxic techniques, have been carried out in the past. A line of volcanic and geothermal activity extends through the western regions of the ice and creates a sub-glacial lake, Grimsvotn, which collapses every five years or so giving rise to the jökulhlaups, a catastrophic flooding which affects considerable areas of the Icelandic coast to the south of Vatnajökull. Proper understanding of the jökulhlaups phenomena can only be achieved if detailed knowledge of ice thickness and related data are available. Established radio echo sounding techniques which have been successfully applied in the polar regions do not work in water-laden ice such as is to be found in the Vatnajökull area.

Estimating the ice thickness of the Müller Ice Cap using an inversion of the shallow ice approximation

2021 ◽  
Author(s):  
Ann-Sofie Priergaard Zinck ◽  
Aslak Grinsted
Keyword(s):  
Remote Sensing Data ◽  
The Arctic ◽  
Ice Thickness ◽  
Potential Contribution ◽  
Mean Squared Errors ◽  
Ice Caps ◽  
Ice Cap ◽  
Regression Parameters ◽  
Digital Elevation ◽  
Elevation Model

<p><span>The ice thickness of the Müller Ice Cap, Arctic Canada, is estimated using regression parameters obtained from an inversion of the shallow ice approximation by the use of a single Operation IceBridge flight line in combination with the glacier outline, surface slope, and elevation. The model is compared with an iterative inverse method of estimating the bedrock topography using PISM as a forward model. In both models the surface elevation is given by the Arctic Digital Elevation Model. The root mean squared errors of the ice thickness on the ice cap is 131 m and 139 m for the shallow ice inversion and the PISM model, respectively. Including the outlet glaciers increases the root mean squared errors to 136 m and 396 m, respectively. </span></p><p><span>The simplicity of the shallow ice inversion model, combined with the good results and the fact that only remote sensing data is needed, means that there is a possibility of applying this model in a global glacier thickness estimate by using the Randolph Glacier Inventory. Most global glacier estimates only provide the volume and not the ice thickness of the glaciers. Hence, global ice thickness models is of great importance in quantifying the potential contribution of sea level rise from the glaciers and ice caps around the globe. </span></p>

scholarly journals Results from the Radio Echo-Sounding on Parts of the Jostedalsbreen Ice Cap, Norway

1986 ◽  
Vol 8 ◽  
pp. 156-158 ◽  
Author(s):  
Arne Chr. Saetrang ◽  
Bjørn Wold
Keyword(s):  
Ice Thickness ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Subglacial Topography ◽  
Echo Sounding

The paper describes instrumentation, navigation methods, and interpretation problems from radio echo-sounding on parts of Jostedalsbreen. A map of the subglacial topography is presented. Ice thickness ranges from 60 m to 600 m with most sections between 150 m and 300 m.

scholarly journals Topography and dynamics of Austfonna, Nordaustlandet, Svalbard, from SAR interferometry

1997 ◽  
Vol 24 ◽  
pp. 403-408 ◽  
Author(s):  
Beverley Unwin ◽  
Duncan Wingham
Keyword(s):  
Sar Interferometry ◽  
Synthetic Aperture ◽  
Drainage Basins ◽  
Ice Caps ◽  
Radar Images ◽  
Differential Interferometry ◽  
Digital Elevation ◽  
Radio Echo Sounding ◽  
Velocity Information ◽  
Elevation Model

The ice caps of Nordaustlandet, Svalbard, represent one of the largest glaciated areas outside of Antarctica and Greenland. They demonstrate a variety of different flow regimes within a comparatively compact area. We report on the first interferometrically derived elevation models and velocity visualisations of Austfonna. This initial investigation had three purposes: to determine whether the coherence and velocity characteristics of the region permitted interferometric survey; to determine the accuracy of derived elevations; and to assess the possibility of investigating time-variant flow of the more dynamic ice bodies using differential interferometry. A trio of coherent synthetic aperture radar images from ERS-1 ’s First Ice Phase was identified. The images were combined to separate the topographic and velocity components of the resultant interferograms. The topographic phase difference was used to produce a digital elevation model of Austfonna. Its accuracy relative to radio-echo-sounding derived tie-points is 8 m and its resolution 40 m. We also present synoptic views of the velocity field of three of Austfonna’s drainage basins, and comment on the extraction of useful velocity information.

scholarly journals Ice-volume changes (1936–1990) and structure of Aldegondabreen, Spitsbergen

2005 ◽  
Vol 42 ◽  
pp. 158-162 ◽  
Author(s):  
F.J. Navarro ◽  
A.F. Glazovsky ◽  
Yu.Ya. Macheret ◽  
E.V. Vasilenko ◽  
M.I. Corcuera ◽  
...  
Keyword(s):  
Radar Data ◽  
Ice Age ◽  
Aerial Photographs ◽  
Joint Analysis ◽  
Topographic Map ◽  
Ice Volume ◽  
Radio Echo Sounding ◽  
Loss Of Mass ◽  
Elevation Model ◽  
Echo Sounding

AbstractAldegondabreen is a small valley glacier, ending on land, located in the Grønfjorden area of Spitsbergen, Svalbard. Airborne radio-echo sounding in 1974/75, using a 440 MHz radar, revealed a polythermal two-layered structure, which has been confirmed by detailed ground-based radio-echo sounding done in 1999 using a 15 MHz monopulse radar. The 1999 radar data reveal an upper cold layer extending down to 90m depth in the southern part of the glacier, where the thickest ice (216 m) was also found. A repeated pattern of diffractions from the southern part of the glacier, at depths of 50–80 m and dipping down-glacier, has been interpreted as an englacial channel which originates in the temperate ice. From joint analysis of the 1936 topographic map, a digital elevation model constructed from 1990 aerial photographs and the subglacial topography determined from radar data, a severe loss of mass during the period 1936–90 has been estimated: a glacier tongue retreat of 930 m, a decrease in area from 8.9 to 7.6 km2, in average ice thickness from 101 to 73 m and in ice volume from 0.950 to 0.558 km3, which are equivalent to an average annual balance of –0.7 mw.e. This is comparable with the only available data of net mass balance for Aldegondabreen (–1.1 and –1.35m w.e. for the balance years 1976/77 and 2002/03) and consistent with the 0.27˚C increase in mean summer air temperature in this zone during 1936–90, as well as the warming in Spitsbergen following the end of the Little Ice Age (LIA), and the general glacier recession trend observed in this region.

scholarly journals Results from the Radio Echo-Sounding on Parts of the Jostedalsbreen Ice Cap, Norway

1986 ◽  
Vol 8 ◽  
pp. 156-158 ◽  
Author(s):  
Arne Chr. Saetrang ◽  
Bjørn Wold
Keyword(s):  
Ice Thickness ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Subglacial Topography ◽  
Echo Sounding

The paper describes instrumentation, navigation methods, and interpretation problems from radio echo-sounding on parts of Jostedalsbreen. A map of the subglacial topography is presented. Ice thickness ranges from 60 m to 600 m with most sections between 150 m and 300 m.

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