Surface and Bedrock Topography of Ice Caps in Iceland, Mapped by Radio Echo-Sounding

1986 ◽  
Vol 8 ◽  
pp. 11-18 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Surface Elevation ◽  
Ice Thickness ◽  
Volcanic Complex ◽  
Glacier Surface ◽  
Ice Caps ◽  
Ice Cap ◽  
North East ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Echo Sounding

Since 1977, large areas on western Vatnajökull have been surveyed by ground-based, radio echo-sounding and the whole ice cap, HofsjökuIl, was surveyed in 1983. Detailed maps of the glacier-surface elevation and the sub-ice bedrock have been compiled. The instrumentation includes a 2–5 MHz, mono-pulse echo-sounder, for continuous profiling, a satellite geoceiver and Loran-C equipment, for navigation, and a precision pressure altimeter. The maps of western Vatnajökull cover about 1500 km2 and are compiled from 1500 km-long sounding lines, which yielded about 50 000 data points for ice thickness and 20 000 points for ice-surface elevation. The maps of HofsjökuIl cover 923 km2, the sounding lines were 1350 km long; 42 000 points were used for determining ice thickness and 30 000 for surface elevation. The maps obtained from these data are the first ones of the ice caps with surface elevation of known accuracy. The bedrock map of western Vatnajökull shows details of volcanic ridges and subglacial valleys, running north-east to south-west, as well as the central, volcanic complexes, Hamarinn, Bárdarbunga, and Grimsvtön and the related fissure swarms. The map of Hofsjökull reveals a large volcanic complex, with a 650 m deep caldera. The landforms in southern Hofsjökull are predominantly aligned from north to south, but those in the northern ice cap run north by 25° east.

scholarly journals Surface and Bedrock Topography of Ice Caps in Iceland, Mapped by Radio Echo-Sounding

1986 ◽  
Vol 8 ◽  
pp. 11-18 ◽  
Author(s):  
Helgi Björnsson
Keyword(s):  
Surface Elevation ◽  
Ice Thickness ◽  
Volcanic Complex ◽  
Glacier Surface ◽  
Ice Caps ◽  
Ice Cap ◽  
North East ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Echo Sounding

Since 1977, large areas on western Vatnajökull have been surveyed by ground-based, radio echo-sounding and the whole ice cap, HofsjökuIl, was surveyed in 1983. Detailed maps of the glacier-surface elevation and the sub-ice bedrock have been compiled. The instrumentation includes a 2–5 MHz, mono-pulse echo-sounder, for continuous profiling, a satellite geoceiver and Loran-C equipment, for navigation, and a precision pressure altimeter. The maps of western Vatnajökull cover about 1500 km2 and are compiled from 1500 km-long sounding lines, which yielded about 50 000 data points for ice thickness and 20 000 points for ice-surface elevation. The maps of HofsjökuIl cover 923 km2, the sounding lines were 1350 km long; 42 000 points were used for determining ice thickness and 30 000 for surface elevation. The maps obtained from these data are the first ones of the ice caps with surface elevation of known accuracy. The bedrock map of western Vatnajökull shows details of volcanic ridges and subglacial valleys, running north-east to south-west, as well as the central, volcanic complexes, Hamarinn, Bárdarbunga, and Grimsvtön and the related fissure swarms. The map of Hofsjökull reveals a large volcanic complex, with a 650 m deep caldera. The landforms in southern Hofsjökull are predominantly aligned from north to south, but those in the northern ice cap run north by 25° east.

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 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 Radio Echo-Sounding of Spitsbergen Glaciers: Problems in the Interpretation of Layer and Bottom Returns

1984 ◽  
Vol 30 (104) ◽  
pp. 16-21 ◽  
Author(s):  
J. A. Dowdeswell ◽  
D.J. Drewry ◽  
O. Liestøl ◽  
O. Orheim
Keyword(s):  
Melting Point ◽  
Water Content ◽  
Ice Thickness ◽  
Drill Core ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Pressure Melting ◽  
Radio Frequencies ◽  
Similar Depth ◽  
Echo Sounding

AbstractAirborne radio echo-sounding of Spitsbergen glaciers during 1980 used 60 MHz SPR1 Mk IV equipment. On several glaciers results showed unambiguous bottom returns at depths 2–3 times those reported in previous Soviet echo-sounding at 440 and 620 MHz. Comparison of 60 MHZ records and independent gravity-surveyed ice thickness for two glaciers agreed to within 10%, whereas Soviet ice thicknesses were only 30–60% of gravity depths. Soviet bed echoes often coincided closely with an internal reflecting horizon recorded by the SPRI Mk IV system, and it is shown that Soviet U.H.F. equipment failed to penetrate to the true glacier bed on a number of ice masses (e.g. Finsterwalderbreen, Kongsvegen, Negribreen). This was probably due to increased absorption and scattering at higher radio frequencies, related to the inhomogeneous nature of Spitsbergen glaciers, which are often at or near the pressure-melting point. Both 60 MHz and U.H.F. equipment seldom recorded bed echoes in ice-cap accumulation areas (e.g. Isachsenfonna), where firn soaking during summer and 10 m temperatures of zero degrees have been observed. An isolated internal reflecting horizon was recorded on many glaciers. It is unlikely to be a moraine layer, but may be related to ice with a water content of 1–2% observed at a similar depth (115 m) in a drill core from Fridtjovbreen.

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.

scholarly journals Digital Mapping of the Nordaustlandet Ice Caps from Airborne Geophysical Investigations

1986 ◽  
Vol 8 ◽  
pp. 51-58 ◽  
Author(s):  
J.A. Dowdeswell ◽  
D.J. Drewry ◽  
A.P.R. Cooper ◽  
M.R. Gorman ◽  
O. Liestøl ◽  
...  
Keyword(s):  
Magnetic Energy ◽  
Direct Access ◽  
Ice Thickness ◽  
Ice Caps ◽  
Digital Mapping ◽  
Ice Surface ◽  
Radio Echo Sounding ◽  
Geophysical Investigations ◽  
Data Source ◽  
Electro Magnetic

Airborne geophysical investigations of the previously tittle-studied Nordaustlandet ice caps (11 150 km2) took place in 1983, using SPRI 60 MHz radio echo-sounding (RES) equipment of 160 dB system performance. RES and navigational data were recorded digitally. Navigation used a ranging system (accurate to ±30 m) from aircraft to ground-based transponders, located by satellite geoceivers, supplemented by the aircraft’s navigational instruments and timed crossings of known features. Ice surface and bedrock elevations were measured, using aircraft pressure altitude, terrain clearance, and ice thickness data. The mean error of 251 crossing points on Austfonna was 11 m. The reduced geophysical data are stored on a direct-access computer database. During 3400 km of flying, Austfonna (8105 km2) was covered by traverses a nominal 5 km apart, whereas a 15 km-spaced grid was flown over Vestfonna (2510 km2). Maps of ice surface morphology and subglacial, bedrock topography were produced for Austfonna and Vestfonna, along with an ice thickness map of Austfonna, Austfonna reaches a maximum surface elevation of 791 m and ice thickness of 583 m. 28% of the bedrock area beneath Austfonna lies below sea level. RES yielded bedrock echoes for 91% of track over Austfonna, but only 52% over Vestfonna. This was probably due to warmer conditions on Vestfonna, resulting in greater absorption and scattering of electro-magnetic energy. Ice surface elevations are a principal data source in the revision of official Norwegian maps of Nordaustlandet.

scholarly journals Miniature high-power impulse transmitter for radio-echo sounding

1994 ◽  
Vol 40 (134) ◽  
pp. 190-194 ◽  
Author(s):  
B. Barry Narod ◽  
Garry K.C. Clarke
Keyword(s):  
High Power ◽  
Yukon Territory ◽  
Ice Thickness ◽  
Maximum Dimension ◽  
Pulse Generators ◽  
Ice Cap ◽  
Bering Glacier ◽  
Radio Echo Sounding ◽  
Towed Arrays ◽  
Echo Sounding

AbstractWe have developed a miniature high-power impulse transmitter for radio-echo sounding of glaciers. It features two synchronous second break-down pulse generators operating in a differential configuration. Specifications include bipolar 550 V pulses having rise times less than 2 ns, 512 Hz repetition rate, 180 mA at 10-14 V d.c. operating power, 5 mA standby current and maximum dimension of 12 cm. Because of its small size and low power consumption, the transmitter is suitable for back-portable systems and for towed arrays. The transmitter first saw service in 1990 on Trapridge Glacier, Yukon Territory. Subsequent copies have been used on Agassiz Ice Cap, Northwest Territories, Bering Glacier, Alaska and elsewhere. To date, the maximum ice thickness measured using this transmitter is 825 m, on temperate Bering Glacier.

Glaciological investigations of surging ice caps in Nordaustlandet, Svalbard, 1983

Polar Record ◽  
1985 ◽  
Vol 22 (139) ◽  
pp. 359-378 ◽  
Author(s):  
D. J. Drewry ◽  
O. Liestøl
Keyword(s):  
Digital System ◽  
Svalbard Archipelago ◽  
Ice Caps ◽  
Ice Cap ◽  
Radio Echo Sounding ◽  
Polar Research Institute ◽  
Echo Sounding ◽  
Research Institute

AbstractDuring spring 1983 a joint British-Norwegian expedition from the Scott Polar Research Institute (SPRI) and the Norsk Polarinstitutt (NP) undertook a programme of glaciological research in the Svalbard archipelago. Work focussed on obtaining airborne radio echo sounding measurements using a newly-constructed digital system and some reconnaissance observations (temperatures, net mass budgets and ice velocities) on the ice caps of Nordaustlandet for the investigation of their surging behaviour. Valley glaciers in Spitsbergen and the ice cap on Kvitøya were also sounded from the air.

scholarly journals Hurd Peninsula glaciers, Livingston Island, Antarctica, as indicators of regional warming: ice-volume changes during the period 1956–2000

2007 ◽  
Vol 46 ◽  
pp. 43-49 ◽  
Author(s):  
C. Molina ◽  
F.J. Navarro ◽  
J. Calvet ◽  
D. García-Sellés ◽  
J.J. Lapazaran
Keyword(s):  
Aerial Photographs ◽  
South Shetland Islands ◽  
Ice Thickness ◽  
Glacier Surface ◽  
Regional Warming ◽  
Ice Volume ◽  
Ice Cap ◽  
Livingston Island ◽  
Radio Echo Sounding ◽  
Volume Estimates

AbstractJohnsons and Hurd Glaciers are the two main glacier units of Hurd Peninsula ice cap, Livingston Island, South Shetland Islands, Antarctica. They presently cover an area of about 10 km2. Johnsons is a tidewater glacier, while Hurd Glacier ends on emerged land. In this paper, we estimate the changes in ice volume during the period 1956–2000, and compare them with the regional meteorological records. The volume-change estimates are based on the comparison of digital terrain models for the glacier surface, constructed from aerial photographs taken by the British Antarctic Survey in 1956 and from our geodetic measurements in 1999/2000. The total volume estimates are based on an ice-thickness map constructed from radio-echo sounding profiles (18–25 MHz) done in 1999–2001, showing maximum ice thickness of about 200 m. We estimate the changes in ice volume during the period 1956–2000 to be –0.108±0.048km3, which represents a 10.0±4.5% decrease from the 1956 total volume of 1.076±0.055km3 and is equivalent to an average annual mass balance of –0.23±0.10mw.e. during 1956–2000. Ice-thickness changes range from –40 to +20 m, averaging –5.5±4.4 m. Most areas show ice thinning; the thickening is limited to a small area within Johnsons Glacier. All glacier fronts, except Johnsons’ calving front, show retreat. These changes are consistent with the regional meteorological records for mean summer temperature, which show a trend of +0.023±0.005˚Ca–1 during the period 1956–2000.

scholarly journals Miniature high-power impulse transmitter for radio-echo sounding

1994 ◽  
Vol 40 (134) ◽  
pp. 190-194 ◽  
Author(s):  
B. Barry Narod ◽  
Garry K.C. Clarke
Keyword(s):  
High Power ◽  
Yukon Territory ◽  
Ice Thickness ◽  
Maximum Dimension ◽  
Pulse Generators ◽  
Ice Cap ◽  
Bering Glacier ◽  
Radio Echo Sounding ◽  
Towed Arrays ◽  
Echo Sounding

AbstractWe have developed a miniature high-power impulse transmitter for radio-echo sounding of glaciers. It features two synchronous second break-down pulse generators operating in a differential configuration. Specifications include bipolar 550 V pulses having rise times less than 2 ns, 512 Hz repetition rate, 180 mA at 10-14 V d.c. operating power, 5 mA standby current and maximum dimension of 12 cm. Because of its small size and low power consumption, the transmitter is suitable for back-portable systems and for towed arrays. The transmitter first saw service in 1990 on Trapridge Glacier, Yukon Territory. Subsequent copies have been used on Agassiz Ice Cap, Northwest Territories, Bering Glacier, Alaska and elsewhere. To date, the maximum ice thickness measured using this transmitter is 825 m, on temperate Bering Glacier.

Sign in / Sign up

Export Citation Format

Share Document