Mapping subglacial surfaces of temperate valley glaciers by two-pass migration of a radio-echo sounding survey

AbstractHigh-resolution maps of the glacier bed are developed through a pseudo-three-dimensional migration of a dense array of radio-echo sounding profiles. Resolution of three-dimensional maps of subglacial surfaces is determined by the radio-echo sounding wavelength, data sparing in the field, and migration. Based on synthetic radio-echo sounding profile experiments, the maximum resolution of the final map cannot exceed one half-wavelength. A methodology of field and processing techniques is outlined to develop a maximum-resolution map of the glacier bed. The field and processing techniques are used to develop a map of the glacier bed below part of Worthington Glacier, a temperate valley glacier in south-central Alaska. The field techniques and the processing steps used on the glacier result in a map of 20 m x 20 m resolution.

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Radio Echo Sounding on a Valley Glacier in East Greenland

Journal of Glaciology ◽

10.3189/s0022143000022723 ◽

1973 ◽

Vol 12 (64) ◽

pp. 87-91 ◽

Cited By ~ 1

Author(s):

J. L. Davis ◽

J. S. Halliday ◽

K. J. Miller

Keyword(s):

The Arctic ◽

Radio Waves ◽

Polar Ice ◽

East Greenland ◽

High Attenuation ◽

Valley Glacier ◽

Radio Echo Sounding ◽

Improved Performance ◽

Temperature Water ◽

Echo Sounding

AbstractAlthough radio echo sounding equipment has been used with success for measuring the thickness of ice sheets in the Arctic and Antarctic, a valley glacier poses the additional problems of echoes from the valley walls, which may obscure the bottom echoes, and a high attenuation of radio waves in the ice. During July and August 1970, a study was carried out on Roslin Gletscher in Stauning Alper, East Greenland, to investigate the problems of radio echo sounding on a valley glacier. Results show that reflections from the valley walls are minimized by using sufficiently directional antennae, but attenuation of the signal in the ice is higher than that in polar ice at the same temperature. Water in and on the ice probably accounts for much of the attenuation, and the use of a lower frequency or measurements before the melt commences should give improved performance.

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New maps of the ice thickness and subglacial topography in Dronning Maud Land, Antarctica, determined by means of airborne radio-echo sounding

Annals of Glaciology ◽

10.3189/172756499781821409 ◽

1999 ◽

Vol 29 ◽

pp. 267-272 ◽

Cited By ~ 29

Author(s):

D. Steinhage ◽

U. Nixdorf ◽

U. Meyer ◽

H. Miller

Keyword(s):

Three Dimensional ◽

Austral Summer ◽

Ice Thickness ◽

Ice Volume ◽

Site Survey ◽

Radio Echo Sounding ◽

First Results ◽

Dronning Maud Land ◽

Subglacial Topography ◽

Echo Sounding

AbstractSince the austral summer of 1994-95 the Alfred Wegener Institute has carried out airborne radio-echo sounding (RES) measurements in Antarctica with its newly designed RES system. Since 1995-96 an ongoing pre-site survey for an ice-coring drill site in Dronning Maud Land has been carried out as part of the European Project for Ice Goring in Antarctica. The survey covers an area of 948 000 km2, with >49 500 km of airborne RES obtained from >200 hours of flight operation flown during the period 1994-97. In this paper, first results of the airborne RES survey are graphically summarized as newly derived maps of the ice thickness and subglacial topography, as well as a three-dimensional view of surface and subglacial bed and outcrop topography, revealing a total ice volume of 1.48 x 106 km3.

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Constraining past accumulation in the central Pine Island Glacier basin, West Antarctica, using radio-echo sounding

Journal of Glaciology ◽

10.3189/2014jog13j180 ◽

2014 ◽

Vol 60 (221) ◽

pp. 553-562 ◽

Cited By ~ 6

Author(s):

Nanna B. Karlsson ◽

Robert G. Bingham ◽

David M. Rippin ◽

Richard C.A. Hindmarsh ◽

Hugh F.J. Corr ◽

...

Keyword(s):

Ice Core ◽

Three Dimensional ◽

Dynamical Instability ◽

West Antarctica ◽

Last Glacial Period ◽

Accumulation Pattern ◽

West Antarctic Ice Sheet ◽

West Antarctic ◽

Radio Echo Sounding ◽

Echo Sounding

AbstractThe potential for future dynamical instability of Pine Island Glacier, West Antarctica, has been addressed in a number of studies, but information on its past remains limited. In this study we use airborne radio-echo sounding (RES) data acquired over Pine Island Glacier to investigate past variations in accumulation pattern. In the dataset a distinctive pattern of layers was identified in the central part of the glacier basin. We use these layers as chronological identifiers in order to construct elevation maps of the internal stratigraphy. The observed internal layer stratigraphy is then compared to calculated stratigraphy from a three-dimensional ice-flow model that has been forced with different accumulation scenarios. The model results indicate that the accumulation pattern is likely to have changed at least twice since the deposition of the deepest identified layer. Additional RES data linked to the Byrd ice core provide an approximate timescale. This timescale suggests that the layers were deposited at the beginning of or during the Holocene period. Thus the widespread changes occurring in the coastal extent of the West Antarctic ice sheet at the end of the last glacial period could have been accompanied by changes in accumulation pattern.

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Past and present accumulation rate reconstruction along the Dome Fuji–Kohnen radio-echo sounding profile, Dronning Maud Land, East Antarctica

Annals of Glaciology ◽

10.3189/172756409789097513 ◽

2009 ◽

Vol 50 (51) ◽

pp. 112-120 ◽

Cited By ~ 20

Author(s):

Philippe Huybrechts ◽

Oleg Rybak ◽

Daniel Steinhage ◽

Frank Pattyn

Keyword(s):

Accumulation Rate ◽

Inversion Layer ◽

Three Dimensional ◽

East Antarctica ◽

Condensation Temperature ◽

Accumulation Rates ◽

Thermomechanical Model ◽

Radio Echo Sounding ◽

Dronning Maud Land ◽

Echo Sounding

AbstractWe used internal ice layers from a radio-echo sounding profile between the Kohnen and Dome Fuji deep drilling sites to infer the spatio-temporal pattern of accumulation rate in this sector of Dronning Maud Land, East Antarctica. Continuous internal reflection horizons can be traced to about half of the ice thickness and have a maximum age of approximately 72.7 ka BP. To infer palaeo-accumulation rates from the dated layers, we derived the thinning functions from a flow calculation with a high-resolution higher-order model of Dronning Maud Land embedded into a three-dimensional thermomechanical model of the Antarctic ice sheet. The method takes into account complex ice-flow dynamics and advection effects that cannot be dealt with using traditional local approaches. We selected seven time intervals over which we determine the average accumulation rate and average surface temperature at the place and time of origin of the layer particles. Our results show lower accumulation rates along eastern parts of the profile for the late Holocene (0–5 ka BP) than are shown by existing maps, which had no surface control points. During the last glacial period we find a substantially lower accumulation rate than predicted by the usual approach linking palaeo-accumulation rates to the condensation temperature above the surface inversion layer. These findings were used to fine-tune the relation between accumulation rate and temperature.

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Radio Echo Sounding on a Valley Glacier in East Greenland

Journal of Glaciology ◽

10.1017/s0022143000022723 ◽

1973 ◽

Vol 12 (64) ◽

pp. 87-91 ◽

Cited By ~ 20

Author(s):

J. L. Davis ◽

J. S. Halliday ◽

K. J. Miller

Keyword(s):

The Arctic ◽

Radio Waves ◽

Polar Ice ◽

East Greenland ◽

High Attenuation ◽

Valley Glacier ◽

Radio Echo Sounding ◽

Improved Performance ◽

Temperature Water ◽

Echo Sounding

AbstractAlthough radio echo sounding equipment has been used with success for measuring the thickness of ice sheets in the Arctic and Antarctic, a valley glacier poses the additional problems of echoes from the valley walls, which may obscure the bottom echoes, and a high attenuation of radio waves in the ice. During July and August 1970, a study was carried out on Roslin Gletscher in Stauning Alper, East Greenland, to investigate the problems of radio echo sounding on a valley glacier. Results show that reflections from the valley walls are minimized by using sufficiently directional antennae, but attenuation of the signal in the ice is higher than that in polar ice at the same temperature. Water in and on the ice probably accounts for much of the attenuation, and the use of a lower frequency or measurements before the melt commences should give improved performance.

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ImpDAR: an open-source impulse radar processor

Annals of Glaciology ◽

10.1017/aog.2020.44 ◽

2020 ◽

Vol 61 (81) ◽

pp. 114-123 ◽

Cited By ~ 1

Author(s):

David A. Lilien ◽

Benjamin H. Hills ◽

Joshua Driscol ◽

Robert Jacobel ◽

Knut Christianson

Keyword(s):

Open Source ◽

Data Archives ◽

Radio Echo Sounding ◽

Cross Platform ◽

Time Correction ◽

And Migration ◽

Ground Penetrating ◽

Full Utilization ◽

Processing Steps ◽

Standard Software

AbstractDespite widespread use of radio-echo sounding (RES) in glaciology and broad distribution of processed radar products, the glaciological community has no standard software for processing impulse RES data. Dependable, fast and collection-system/platform-independent processing flows could facilitate comparison between datasets and allow full utilization of large impulse RES data archives and new data. Here, we present ImpDAR, an open-source, cross-platform, impulse radar processor and interpreter, written primarily in Python. The utility of this software lies in its collection of established tools into a single, open-source framework. ImpDAR aims to provide a versatile standard that is accessible to radar-processing novices and useful to specialists. It can read data from common commercial ground-penetrating radars (GPRs) and some custom-built RES systems. It performs all the standard processing steps, including bandpass and horizontal filtering, time correction for antenna spacing, geolocation and migration. After processing data, ImpDAR's interpreter includes several plotting functions, digitization of reflecting horizons, calculation of reflector strength and export of interpreted layers. We demonstrate these capabilities on two datasets: deep (~3000 m depth) data collected with a custom (3 MHz) system in northeast Greenland and shallow (<100 m depth, 500 MHz) data collected with a commercial GPR on South Cascade Glacier in Washington.

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Using internal layers from the Greenland ice sheet, identified from radio-echo sounding data, with numerical models

Annals of Glaciology ◽

10.3189/172756403781815438 ◽

2003 ◽

Vol 37 ◽

pp. 325-330 ◽

Cited By ~ 10

Author(s):

Duncan J. Baldwin ◽

Jonathan L. Bamber ◽

Antony J. Payne ◽

Russel L. Layberry

Keyword(s):

Velocity Field ◽

Numerical Models ◽

Accumulation Rate ◽

Three Dimensional ◽

Ice Sheet ◽

Internal Layers ◽

Accumulation Rates ◽

Radio Echo Sounding ◽

North Greenland ◽

Echo Sounding

AbstractSpatially extensive internal layers have been traced in airborne radio-echo sounding (RES) data collected over Greenland during the late 1990s. By linking internal layers within individual flight-lines at crossover points, it is possible to identify spatially continuous layers that are interpreted as isochronous surfaces. Several of the survey lines pass over the GRIP core site, and this allows us to use the published GRIP age–depth relationship to accurately date these surfaces. Two layers, with ages of 3891 and 6956 years BP, have been traced over a large part of North Greenland. Accurately dated and spatially continuous isochrones are valuable for both assimilation within, and verification of, numerical models. For example, comparison of isochronous surfaces from a numerical simulation with those layers observed in RES data can be used to inform the choice of parameters (e.g. rheology) and climate history used to force a numerical model. To demonstrate the potential of the RES data, two layers for North Greenland were used to determine palaeo-accumulation rates. The inversion from layer depth to accumulation rate requires a three-dimensional velocity field. This velocity field is constructed by combining a two-dimensional balance-velocity field with an assumed vertical structure for the horizontal velocity. The isochronous-layer derived accumulation rates were compared with the Bales and others (2001) rates. A larger east–west gradient was found across the central ice divide for the derived accumulation rate, suggesting a trend in the Holocene accumulation rates for this region. The layers were also compared with isochronous surfaces derived from simulations of a three-dimensional thermodynamic ice-sheet model. Using the isochronous-layer derived accumulation rates to force the model improved the match between modelled and observed layers.

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Three-Dimensional Structure of Rotavirus-Fab Complex

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100179944 ◽

1990 ◽

Vol 48 (1) ◽

pp. 238-239

Author(s):

B.V.V. Prasad ◽

E. Marietta ◽

J.W. Burns ◽

M.K. Estes ◽

W. Chiu

Keyword(s):

Image Processing ◽

Smooth Surface ◽

Three Dimensional ◽

Outer Shell ◽

Dimensional Structure ◽

Structural Studies ◽

Cell Penetration ◽

Electron Cryomicroscopy ◽

Image Processing Techniques ◽

Processing Techniques

Rotaviruses are spherical, double-shelled particles. They have been identified as a major cause of infantile gastroenteritis worldwide. In our earlier studies we determined the three-dimensional structures of double-and single-shelled simian rotavirus embedded in vitreous ice using electron cryomicroscopy and image processing techniques to a resolution of 40Å. A distinctive feature of the rotavirus structure is the presence of 132 large channels spanning across both the shells at all 5- and 6-coordinated positions of a T=13ℓ icosahedral lattice. The outer shell has 60 spikes emanating from its relatively smooth surface. The inner shell, in contrast, exhibits a bristly surface made of 260 morphological units at all local and strict 3-fold axes (Fig.l).The outer shell of rotavirus is made up of two proteins, VP4 and VP7. VP7, a glycoprotein and a neutralization antigen, is the major component. VP4 has been implicated in several important functions such as cell penetration, hemagglutination, neutralization and virulence. From our earlier studies we had proposed that the spikes correspond to VP4 and the rest of the surface is composed of VP7. Our recent structural studies, using the same techniques, with monoclonal antibodies specific to VP4 have established that surface spikes are made up of VP4.

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Characteristics of relocated hypocenters of the 2018 M6.7 Hokkaido Eastern Iburi earthquake and its aftershocks with a three-dimensional seismic velocity structure

Earth Planets and Space ◽

10.1186/s40623-019-1100-0 ◽

2019 ◽

Vol 71 (1) ◽

Cited By ~ 1

Author(s):

Saeko Kita

Keyword(s):

Seismic Velocity ◽

Three Dimensional ◽

Double Difference ◽

Earthquake Catalog ◽

Seismic Structure ◽

Depth Limit ◽

High Attenuation ◽

South Central ◽

Collision Zone ◽

Hidaka Collision Zone

AbstractI relocated the hypocenters of the 2018 M6.7 Hokkaido Eastern Iburi earthquake and its surrounding area, using a three-dimensional seismic structure, the double-difference relocation method, and the JMA earthquake catalog. After relocation, the focal depth of the mainshock became 35.4 km. As previous studies show, in south-central Hokkaido, the Hidaka collision zone is formed, and anomalous deep and thickened forearc crust material is subducting at depths of less than 70 km. The mainshock and its aftershocks are located at depths of approximately 10 to 40 km within the lower crust of the anomalous deep and thickened curst near the uppermost mantle material intrusions in the northwestern edge of this Hidaka collision zone. Like the two previous large events, the aftershocks of this event incline steeply eastward and appear to be distributed in the deeper extension of the Ishikari-teichi-toen fault zone. The highly inclined fault in the present study is consistent with a fault model by a geodetic analysis with InSAR. The aftershocks at depths of 10 to 20 km are located at the western edge of the high-attenuation (low-Qp) zone. These kinds of relationships between hypocenters and materials are the same as the 1970 and 1982 events in the Hidaka collision zone. The anomalous large focal depths of these large events compared with the average depth limit of inland earthquakes in Japan could be caused by the locally lower temperature in south-central Hokkaido. This event is one of the approximately M7 large inland earthquakes that occurred repeatedly at a recurrence interval of approximately 40 years and is important in the collision process in the Hidaka collision zone.

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