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

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.

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

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.

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

1987 ◽  
Vol 9 ◽  
pp. 221-224 ◽  
Author(s):  
Minoru Yoshida ◽  
Kazunobu Yamashita ◽  
Shinji Mae
Keyword(s):  
Cross Sections ◽  
Flow Line ◽  
Bottom Topography ◽  
Ice Core ◽  
Ice Sheet ◽  
Internal Layers ◽  
Radio Echo Sounding ◽  
Dronning Maud Land ◽  
Field Season ◽  
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.

scholarly journals Airborne Radio Echo-Sounding in Shirase Glacier Drainage Basin, Antarctica

1987 ◽  
Vol 9 ◽  
pp. 160-165
Author(s):  
S. Mae ◽  
M. Yoshida
Keyword(s):  
Main Part ◽  
Drainage Basin ◽  
Ice Sheet ◽  
Main Flow ◽  
Ice Thickness ◽  
Echo Intensity ◽  
Flow Area ◽  
Bedrock Topography ◽  
Radio Echo Sounding ◽  
Echo Sounding

Airborne radio echo-sounding was carried out in order to measure the thickness of the ice sheet in the Shirase Glacier drainage basin and map the bedrock topography. It was found that the elevation of bedrock was approximately at sea-level from Shirase Glacier to 100 km up-stream of the glacier and thereafter it was 500–100 m higher. Investigation of the echo intensity reflected from the bedrock indicates that at ice thicknesses less than 1000 m absorption was about 5.2 dB/100 m, but at greater ice thicknesses echo intensity did not depend upon the ice thickness but became approximately constant. Where ice thicknesses were greater than 1000 m in the main flow area of the Shirase Glacier drainage basin, the reflection strengths of about 9 dB were greater than outside the basin. Since the increase in echo intensity was considered to be due to the existence of water, the strong echo observed in the main part of the basin supported an hypothesis that the base of the basin was wet and the ice sheet was sliding on the bedrock.

scholarly journals Characteristics of Ice Flow in Marie Byrd Land, Antarctica

1979 ◽  
Vol 24 (90) ◽  
pp. 63-75 ◽  
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.

scholarly journals Characteristics of Ice Flow in Marie Byrd Land, Antarctica

1979 ◽  
Vol 24 (90) ◽  
pp. 63-75 ◽  
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.

scholarly journals Airborne Radio Echo-Sounding in Shirase Glacier Drainage Basin, Antarctica

1987 ◽  
Vol 9 ◽  
pp. 160-165 ◽  
Author(s):  
S. Mae ◽  
M. Yoshida
Keyword(s):  
Main Part ◽  
Drainage Basin ◽  
Ice Sheet ◽  
Main Flow ◽  
Ice Thickness ◽  
Echo Intensity ◽  
Flow Area ◽  
Bedrock Topography ◽  
Radio Echo Sounding ◽  
Echo Sounding

Airborne radio echo-sounding was carried out in order to measure the thickness of the ice sheet in the Shirase Glacier drainage basin and map the bedrock topography. It was found that the elevation of bedrock was approximately at sea-level from Shirase Glacier to 100 km up-stream of the glacier and thereafter it was 500–100 m higher. Investigation of the echo intensity reflected from the bedrock indicates that at ice thicknesses less than 1000 m absorption was about 5.2 dB/100 m, but at greater ice thicknesses echo intensity did not depend upon the ice thickness but became approximately constant. Where ice thicknesses were greater than 1000 m in the main flow area of the Shirase Glacier drainage basin, the reflection strengths of about 9 dB were greater than outside the basin. Since the increase in echo intensity was considered to be due to the existence of water, the strong echo observed in the main part of the basin supported an hypothesis that the base of the basin was wet and the ice sheet was sliding on the bedrock.

scholarly journals Detecting and Searching for subglacial lakes through airborne radio-echo sounding in Princess Elizabeth Land (PEL), Antarctica

2020 ◽  
Vol 163 ◽  
pp. 04002
Author(s):  
Xiangbin Cui ◽  
Shinan Lang ◽  
Jingxue Guo ◽  
Bo Sun
Keyword(s):  
Remote Sensing ◽  
Ice Sheet ◽  
Extreme Environment ◽  
Ice Flow ◽  
Preliminary Results ◽  
Lake Vostok ◽  
Subglacial Lake ◽  
Radio Echo Sounding ◽  
Subglacial Lakes ◽  
Echo Sounding

Over 400 subglacial lakes were discovered in Antarctica through radio-echo sounding (RES) method and remote sensing. Subglacial lakes have significance in lubricating ice-bedrock interface and enhancing ice flow. Moreover, ancient lives may exist in the extreme environment. Since 2015, the “Snow Eagle 601” BT-67 airborne platform has been deployed and applied to map ice sheet and bedrock of Princess Elizabeth Land. One of great motivations of airborne surveys is to detect and search for subglacial lakes in the region. In this paper, we provided preliminary results of RES over both old and new discovered lakes, including Lake Vostok, a potential second large subglacial lake and other lakes beneath interior of the ice sheet in Antarctica.

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

1987 ◽  
Vol 9 ◽  
pp. 221-224
Author(s):  
Minoru Yoshida ◽  
Kazunobu Yamashita ◽  
Shinji Mae
Keyword(s):  
Cross Sections ◽  
Flow Line ◽  
Bottom Topography ◽  
Ice Core ◽  
Ice Sheet ◽  
Internal Layers ◽  
Radio Echo Sounding ◽  
Dronning Maud Land ◽  
Field Season ◽  
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.

scholarly journals Glaciodynamic context of subglacial bedform generation and preservation

1999 ◽  
Vol 28 ◽  
pp. 23-32 ◽  
Author(s):  
Chris D. Clark
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Shear Stresses ◽  
Morphometric Characteristics ◽  
Glacial Cycle ◽  
Sheet Flow ◽  
Ice Flow ◽  
Ice Stream ◽  
Highly Sensitive ◽  
Basal Shear

AbstractSubglacially-produced drift lineations provide spatially extensive evidence of ice flow that can be used to aid reconstructions of the evolution of former ice sheets. Such reconstructions, however, are highly sensitive to assumptions made about the glaciodynamic context of lineament generation; when during the glacial cycle and where within the ice sheet were they produced. A range of glaciodynamic contexts are explored which include: sheet-flow submarginally restricted; sheet-flow pervasive; sheet- flow patch; ice stream; and surge or re-advance. Examples of each are provided. The crux of deciphering the appropriate context is whether lineations were laid down time-trans-gressively or isochronously. It is proposed that spatial and morphometric characteristics of lineations, and their association with other landforms, can be used as objective criteria to help distinguish between these cases.A logically complete ice-sheet reconstruction must also account for the observed patches of older lineations and other relict surfaces and deposits that have survived erasure by subsequent ice flow. A range of potential preservation mechanisms are explored, including: cold- based ice; low basal-shear stresses; shallowing of the deforming layer; and basal uncoupling.

scholarly journals Precise altimetric topography in ice-sheet flow studies

1993 ◽  
Vol 17 ◽  
pp. 195-200 ◽  
Author(s):  
F. Remy ◽  
J.F. Minster
Keyword(s):  
Activation Energy ◽  
Flow Direction ◽  
Ice Sheet ◽  
Rheological Parameters ◽  
Least Squares Regression ◽  
Sheet Flow ◽  
Ice Flow ◽  
Flow Models ◽  
Altimetric Data ◽  
Basal Shear

The precision of radar altimetry above an ice sheet can improve glaciological studies such as mass balance surveys or ice-sheet flow models, the first by comparing altimetric data at different times (see this issue), the second by testing or constraining models with data. This paper is a first step towards the latter. From a precise topography deduced by inversion of altimetric data (Remy and others, 1989), we calculate ice-flow direction, balance velocity and basal shear stress. The rheological parameters involved in the relation linking velocity, stress and temperature are then derived by least-squares regression. Ice flow is well represented by setting the Glen parameter,nto 1 ± 0.25 and the activation energy as 70 ± 10 kJ mol−1.

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