Bottom Topography and Internal Layers in East Dronning Maud Land, East Antarctica, from 179 MHz Radio Echo-Sounding

Extensive echo-sounding was carried out in east Dronning Maud Land during the 1984 field season. A 179 MHz radar with separate transmitting and receiving antennae was used and the echoes were recorded by a digital system to detect minute reflections. The results gave cross-sections of the ice sheet along traverse routes from lat. 69 °S. to 75°S, Detailed observations on the ground at Mizuho station showed that there was elliptical polarization in the internally reflected echoes when two antennae, kept in parallel with each other, were rotated horizontally. The internal echoes were most clearly distinguished when the antenna azimuth was oriented perpendicular to the flow line of the ice sheet. The internal echoes with a high reflection coefficient were detected at depths of 500–700 m and 1000–1500 m at Mizuho station. Since a distinct internal echo at a depth of 500 m coincides with a 5 cm thick volcanic ash-laden ice layer found in the 700 m ice core taken near the observation site, these echoes may correspond to the acidic ice layers formed by past volcanic events in east Dronning Maud Land.

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Geophysical investigations of ice-sheet internal layering and deformation in the Dome C region of central East Antarctica

Journal of Glaciology ◽

10.3189/172756500781833223 ◽

2000 ◽

Vol 46 (152) ◽

pp. 161-166 ◽

Cited By ~ 11

Author(s):

Richard Hodgkins ◽

Martin J. Siegert ◽

Julian A. Dowdeswell

Keyword(s):

Cross Sections ◽

Ice Core ◽

Three Dimensional ◽

Ice Sheet ◽

Aerosol Deposition ◽

East Antarctica ◽

Internal Layers ◽

Radio Echo Sounding ◽

Geophysical Investigations ◽

The One

AbstractNew maps are presented of three internal ice-sheet radio-echo sounding (RES) layers in the region 73.5–75.75° S, 120–127° E (56 000 km2) around Dome C, central East Antarctica. These layers represent horizons of enhanced acidity resulting from volcanic aerosol deposition, identified from analogue RES data. They are continuous over the entire mapped area, and constitute deformation markers in the ice column. Internal RES layers were initially identified from discrete radar power reflection coefficient profiles and subsequently digitized directly from prints of ice-sheet cross-sections, acquired by continuous RES profiling. Georeferenced vector data are used to generate a 5 km gridcell raster of depth for each internal RES layer, as a basis for contour mapping. Ice deformation in the Dome C region is significant because this is the location of the European Project for Ice Coring in Antarctica. Since internal layers are isochronous, the one-dimensional ice-core data at Dome C can be correlated over the survey area to produce a three-dimensional context.

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Internal structure of the ice sheet between Kohnen station and Dome Fuji, Antarctica, revealed by airborne radio-echo sounding

Annals of Glaciology ◽

10.3189/2013aog64a113 ◽

2013 ◽

Vol 54 (64) ◽

pp. 163-167 ◽

Cited By ~ 9

Author(s):

Daniel Steinhage ◽

Sepp Kipfstuhl ◽

Uwe Nixdorf ◽

Heinz Miller

Keyword(s):

Internal Structure ◽

Accumulation Rate ◽

Ice Core ◽

Ice Sheet ◽

Ice Cores ◽

Internal Layers ◽

Radio Echo Sounding ◽

Depth Scale ◽

Echo Sounding

Abstract This study aims to demonstrate that deep ice cores can be synchronized using internal horizons in the ice between the drill sites revealed by airborne radio-echo sounding (RES) over a distance of >1000km, despite significant variations in glaciological parameters, such as accumulation rate between the sites. In 2002/03 a profile between the Kohnen station and Dome Fuji deep ice-core drill sites, Antarctica, was completed using airborne RES. The survey reveals several continuous internal horizons in the RES section over a length of 1217 km. The layers allow direct comparison of the deep ice cores drilled at the two stations. In particular, the counterpart of a visible layer observed in the Kohnen station (EDML) ice core at 1054 m depth has been identified in the Dome Fuji ice core at 575 m depth using internal RES horizons. Thus the two ice cores can be synchronized, i.e. the ice at 1560 m depth (at the bottom of the 2003 EDML drilling) is ∼49ka old according to the Dome Fuji age/depth scale, using the traced internal layers presented in this study.

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Distribution of Reflected Power From the Bed by Radio Echo-Sounding in the Shirase Glacier Drainage Area, East Dronning Maud Land, Antarctica

Annals of Glaciology ◽

10.3189/s0260305500007072 ◽

1989 ◽

Vol 12 ◽

pp. 124-126

Author(s):

Hirokazu Ohmae ◽

Fumihiko Nishio ◽

Shinji Mae

Keyword(s):

Drainage Basin ◽

Ice Sheet ◽

Ice Flow ◽

Boundary Area ◽

Radio Echo Sounding ◽

Dronning Maud Land ◽

Reflected Power ◽

Basal Shear ◽

Reflection Intensity ◽

Echo Sounding

A large part of the area of the Shirase Glacier drainage basin has been surveyed by airborne (operating frequency: 179 MHz) and ground-based (60 MHz) radio echo-sounding to define the bedrock topography and to investigate the condition of bed/ice interface since 1982.It is shown that the reflection intensity from the bed, which is corrected for attenuation in the ice sheet, has a higher value for reflection intensity in the down-stream area of Shirase Glacier than in the up-stream area. The area of strongest intensity of reflection from the bed coincides with the area for which the calculated temperature at the bed is above −1°C. The boundary area between the highest and lowest values of corrected reflected intensity corresponds to the area of decreasing basal shear stress. It is found that the distribution of high corrected reflection intensity corresponds to the area of thinning of the ice sheet, which has been measured by ice-flow observation in the Shirase Glacier drainage basin.

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Relation between ice sheet internal radio-echo reflections and ice fabric at Mizuho Station, Antarctica

Annals of Glaciology ◽

10.3189/s0260305500012957 ◽

1993 ◽

Vol 17 ◽

pp. 269-275 ◽

Cited By ~ 4

Author(s):

Shuji Fujita ◽

Shinji Mae

Keyword(s):

Dielectric Permittivity ◽

Flow Line ◽

Ice Core ◽

Ice Sheet ◽

Permittivity Tensor ◽

Observation Data ◽

Dielectric Permittivity Tensor ◽

Radio Echo Sounding ◽

Oriented Parallel ◽

Transmitting Antenna

The relationship between ice fabric and the internal radio-echo reflections was investigated using observation data collected at Mizuho Station, Antarctica. The data were obtained by 179 MHz radio-echo sounding and the ice fabric was measured from 700 m Mizuho ice core. The dielectric permittivity tensor at given depths in the ice sheet was calculated from the ice fabric.The calculated dielectric permittivity tensor showed that the ice sheet at Mizuho Station is a uniaxially birefringent medium. The symmetrical axis of rotation was the same as the flow line. In such a medium, theory predicts that the electric field vectors are allowed only in the two directions parallel and perpendicular to the flow line. The prediction coincided well with the observation: a strong signal was observed only when the transmitting antenna and the receiving antenna, kept parallel to one another, were oriented parallel or perpendicular to the flow line. However, the observed signal strength in these two directions differed from one another at each depth.It is also shown that the power reflection coefficient due to the variation of ice fabric with depth is of approximately the same order as that due to the density change and is large enough to produce the predominant internal radio-echo reflections.

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Distribution of Reflected Power From the Bed by Radio Echo-Sounding in the Shirase Glacier Drainage Area, East Dronning Maud Land, Antarctica

Annals of Glaciology ◽

10.1017/s0260305500007072 ◽

1989 ◽

Vol 12 ◽

pp. 124-126 ◽

Cited By ~ 1

Author(s):

Hirokazu Ohmae ◽

Fumihiko Nishio ◽

Shinji Mae

Keyword(s):

Drainage Basin ◽

Ice Sheet ◽

Ice Flow ◽

Boundary Area ◽

Radio Echo Sounding ◽

Dronning Maud Land ◽

Reflected Power ◽

Basal Shear ◽

Reflection Intensity ◽

Echo Sounding

A large part of the area of the Shirase Glacier drainage basin has been surveyed by airborne (operating frequency: 179 MHz) and ground-based (60 MHz) radio echo-sounding to define the bedrock topography and to investigate the condition of bed/ice interface since 1982. It is shown that the reflection intensity from the bed, which is corrected for attenuation in the ice sheet, has a higher value for reflection intensity in the down-stream area of Shirase Glacier than in the up-stream area. The area of strongest intensity of reflection from the bed coincides with the area for which the calculated temperature at the bed is above −1°C. The boundary area between the highest and lowest values of corrected reflected intensity corresponds to the area of decreasing basal shear stress. It is found that the distribution of high corrected reflection intensity corresponds to the area of thinning of the ice sheet, which has been measured by ice-flow observation in the Shirase Glacier drainage basin.

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Tracing the depth of the Holocene ice in North Greenland from radio-echo sounding data

Annals of Glaciology ◽

10.3189/2013aog64a057 ◽

2013 ◽

Vol 54 (64) ◽

pp. 44-50 ◽

Cited By ~ 25

Author(s):

Nanna B. Karlsson ◽

Dorthe Dahl-Jensen ◽

S. Prasad Gogineni ◽

John D. Paden

Keyword(s):

Ice Core ◽

Ice Sheet ◽

Greenland Ice Sheet ◽

Ice Cores ◽

The Holocene ◽

Fitting Method ◽

Radio Echo Sounding ◽

North Greenland ◽

Echo Sounding

Abstract Radio-echo sounding surveys over the Greenland ice sheet show clear, extensive internal layering, and comparisons with age–depth scales from deep ice cores allow for dating of the layering along the ice divide. We present one of the first attempts to extend the dated layers beyond the ice core drill sites by locating the depth of the Bølling–Allerød transition in >400 flight-lines using an automated fitting method. Results show that the transition is located in the upper one-third of the ice column in the central part of North Greenland, while the transition lowers towards the margin. This pattern mirrors the present surface accumulation, and also indicates that a substantial amount of pre-Holocene ice must be present in central North Greenland.

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Improved method to determine radio-echo sounding reflector depths from ice-core profiles of permittivity and conductivity

Journal of Glaciology ◽

10.3189/172756506781828674 ◽

2006 ◽

Vol 52 (177) ◽

pp. 299-310 ◽

Cited By ~ 37

Author(s):

Olaf Eisen ◽

Frank Wilhelms ◽

Daniel Steinhage ◽

Jakob Schwander

Keyword(s):

Wave Propagation ◽

Wave Speed ◽

Ice Core ◽

Synthetic Data ◽

Ice Cores ◽

Radio Echo Sounding ◽

Dronning Maud Land ◽

Clear Identification ◽

Cross Correlations ◽

Echo Sounding

AbstractWe present a technique that modifies and extends down-hole target methods to provide absolute measures of uncertainty in radar-reflector depth of origin. We use ice-core profiles to model wave propagation and reflection, and then cross-correlate the model results with radio-echo sounding (RES) data to identify the depth of reflector events. Stacked traces recorded with RES near the EPICA drill site in Dronning Maud Land, Antarctica, provide reference radargrams, and dielectric properties along the deep ice core form the input data to a forward model of wave propagation that produces synthetic radargrams. Cross-correlations between synthetic and RES radargrams identify differences in propagation wave speed. They are attributed to uncertainties in pure-ice permittivity and are used for calibration. Removing conductivity peaks results in the disappearance of related synthetic reflections and enables the unambiguous relation of electric signatures to RES features. We find that (i) density measurements with g-attenuation or dielectric profiling are too noisy below the firn–ice transition to allow clear identification of reflections, (ii) single conductivity peaks less than 0.5 m wide cause the majority of prominent reflections beyond a travel time of about 10 µs (~900m depth) and (iii) some closely spaced conductivity peaks within a range of 1–2m cannot be resolved within the RES or synthetic data. Our results provide a depth accuracy to allow synchronization of age–depth profiles of ice cores by RES, modeling of isochronous internal structures, and determination of wave speed and of pure-ice properties. The technique successfully operates with dielectric profiling and electrical conductivity measurements, suggesting that it can be applied at other ice cores and drill sites.

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Characteristics of Ice Flow in Marie Byrd Land, Antarctica

Journal of Glaciology ◽

10.3189/s0022143000014659 ◽

1979 ◽

Vol 24 (90) ◽

pp. 63-75 ◽

Cited By ~ 2

Author(s):

K. E. Rose

Keyword(s):

Flow Line ◽

Landsat Imagery ◽

Ice Sheet ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Flow ◽

Ross Ice Shelf ◽

Radio Echo Sounding ◽

Echo Sounding

AbstractExtensive radio echo-sounding has mapped the part of West Antarctica between Byrd Station, the Whitmore Mountains, the Transantarctic Mountains, and the Ross Ice Shelf. The ice sheet in this area is dominated by five major sub-parallel ice streams (A–E), which are up to 100 km wide and extend inland from the grounding line of the Ross Ice Shelf for about 400 km. Their positions have been determined by crevassing seen on radio echo-sounding records, trimetrogon photographs, and Landsat imagery. The ice streams are characterized by their flat transverse cross-sections, while the intervening ice sheet exhibits domes and ridges. Ice flow lines are defined from the ice-surface contour pattern and the trend of the ice streams. It is apparent from this work that the flow line passing through Byrd Station joins ice stream D.The bedrock of the area is relatively smooth near the Ross Ice Shelf, becoming rougher near Byrd Station and especially so near the Whitmore Mountains. Bedrock troughs, which control the positions of the ice streams, are believed to have a tectonic origin.In this paper the role of the ice streams in the glaciological regime of West Antarctica is investigated from radio-echo data and estimates of balance velocity, basal shear stress, and basal temperatures.

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Characteristics of Ice Flow in Marie Byrd Land, Antarctica

Journal of Glaciology ◽

10.1017/s0022143000014659 ◽

1979 ◽

Vol 24 (90) ◽

pp. 63-75 ◽

Cited By ~ 188

Author(s):

K. E. Rose

Keyword(s):

Flow Line ◽

Landsat Imagery ◽

Ice Sheet ◽

West Antarctica ◽

Ice Shelf ◽

Ice Streams ◽

Ice Flow ◽

Ross Ice Shelf ◽

Radio Echo Sounding ◽

Echo Sounding

AbstractExtensive radio echo-sounding has mapped the part of West Antarctica between Byrd Station, the Whitmore Mountains, the Transantarctic Mountains, and the Ross Ice Shelf. The ice sheet in this area is dominated by five major sub-parallel ice streams (A–E), which are up to 100 km wide and extend inland from the grounding line of the Ross Ice Shelf for about 400 km. Their positions have been determined by crevassing seen on radio echo-sounding records, trimetrogon photographs, and Landsat imagery. The ice streams are characterized by their flat transverse cross-sections, while the intervening ice sheet exhibits domes and ridges. Ice flow lines are defined from the ice-surface contour pattern and the trend of the ice streams. It is apparent from this work that the flow line passing through Byrd Station joins ice stream D.The bedrock of the area is relatively smooth near the Ross Ice Shelf, becoming rougher near Byrd Station and especially so near the Whitmore Mountains. Bedrock troughs, which control the positions of the ice streams, are believed to have a tectonic origin.In this paper the role of the ice streams in the glaciological regime of West Antarctica is investigated from radio-echo data and estimates of balance velocity, basal shear stress, and basal temperatures.

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