scholarly journals Study of Deformations within Ice Sheets due to Bottom Undulations by Means of Radio Echo-Sounding

1979 ◽  
Vol 24 (90) ◽  
pp. 513 ◽  
Author(s):  
S. Overgaard ◽  
K. Rasmussen
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Flow Lines ◽  
Radio Echo Sounding ◽  
Abstract Data ◽  
Surface Profiles ◽  
Technical University ◽  
Glacier Flow ◽  
Echo Sounding

Abstract In order to test the theory of glacier flow over bedrock undulations presented by S. J. Johnsen, K. Rasmussen, and N.Reeh in the accompanying abstract, data from the E.G.I.G. and the Dye-3 flow lines on the Greenland ice sheet have been analysed. The data comprise surface profiles measured by conventional techniques, and ice thicknesses and depths of internal isochronic layers obtained by the Technical University of Denmark by means of radio echo-soundings.

scholarly journals Study of Deformations within Ice Sheets due to Bottom Undulations by Means of Radio Echo-Sounding

1979 ◽  
Vol 24 (90) ◽  
pp. 513-513
Author(s):  
S. Overgaard ◽  
K. Rasmussen
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Flow Lines ◽  
Radio Echo Sounding ◽  
Abstract Data ◽  
Surface Profiles ◽  
Technical University ◽  
Glacier Flow ◽  
Echo Sounding

AbstractIn order to test the theory of glacier flow over bedrock undulations presented by S. J. Johnsen, K. Rasmussen, and N.Reeh in the accompanying abstract, data from the E.G.I.G. and the Dye-3 flow lines on the Greenland ice sheet have been analysed. The data comprise surface profiles measured by conventional techniques, and ice thicknesses and depths of internal isochronic layers obtained by the Technical University of Denmark by means of radio echo-soundings.

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

2013 ◽  
Vol 54 (64) ◽  
pp. 44-50 ◽  
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.

scholarly journals Isochronous information in a Greenland ice sheet radio echo sounding data set

2014 ◽  
Vol 41 (5) ◽  
pp. 1593-1599 ◽  
Author(s):  
Louise C. Sime ◽  
Nanna B. Karlsson ◽  
John D. Paden ◽  
S. Prasad Gogineni
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Data Set ◽  
Radio Echo Sounding ◽  
Echo Sounding

Four decades of radar-echo sounding: The past, present, and future of radar applications for understanding subglacial environments 

2021 ◽  
Author(s):  
Winnie Chu
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Thermal Conditions ◽  
Machine Learning Algorithms ◽  
Polar Ice Sheets ◽  
Radar Echo ◽  
Radar Applications ◽  
Bed Roughness ◽  
Subglacial Environments ◽  
Echo Sounding

<p>Airborne radar sounding observations have been instrumental in understanding subglacial environments and basal processes of ice sheets. Since the advent of analog radar-echo sounding (RES) system in the early 1970s, there have been tremendous innovations in both RES hardware and signal processing techniques. These technological advancements have provided high-resolution ice thickness measurements, improved detection and characterization of subglacial hydrology, as well as improved understanding of basal thermal conditions, bed roughness and geomorphology, and other processes that govern the basal boundary of the polar ice sheets. In this talk, I will provide an overview of the recent developments in radar processing approaches and system designs and highlight some of the new understanding of ice sheet subglacial processes that emerge from these breakthroughs. I will end by discussing areas where future radar applications and discoveries may be possible, including the utilization of machine learning algorithms, space-borne radar missions, and ground-based passive radar platforms to provide long-term monitoring of ice sheet subglacial environments.</p>

scholarly journals Last Interglacial climate and sea-level evolution from a coupled ice sheet–climate model

2016 ◽  
Vol 12 (12) ◽  
pp. 2195-2213 ◽  
Author(s):  
Heiko Goelzer ◽  
Philippe Huybrechts ◽  
Marie-France Loutre ◽  
Thierry Fichefet
Keyword(s):  
Surface Temperature ◽  
Sea Level ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Last Interglacial ◽  
A Minor ◽  
The Antarctic ◽  
The Impact ◽  
And Sea Level

Abstract. As the most recent warm period in Earth's history with a sea-level stand higher than present, the Last Interglacial (LIG,  ∼  130 to 115 kyr BP) is often considered a prime example to study the impact of a warmer climate on the two polar ice sheets remaining today. Here we simulate the Last Interglacial climate, ice sheet, and sea-level evolution with the Earth system model of intermediate complexity LOVECLIM v.1.3, which includes dynamic and fully coupled components representing the atmosphere, the ocean and sea ice, the terrestrial biosphere, and the Greenland and Antarctic ice sheets. In this setup, sea-level evolution and climate–ice sheet interactions are modelled in a consistent framework.Surface mass balance change governed by changes in surface meltwater runoff is the dominant forcing for the Greenland ice sheet, which shows a peak sea-level contribution of 1.4 m at 123 kyr BP in the reference experiment. Our results indicate that ice sheet–climate feedbacks play an important role to amplify climate and sea-level changes in the Northern Hemisphere. The sensitivity of the Greenland ice sheet to surface temperature changes considerably increases when interactive albedo changes are considered. Southern Hemisphere polar and sub-polar ocean warming is limited throughout the Last Interglacial, and surface and sub-shelf melting exerts only a minor control on the Antarctic sea-level contribution with a peak of 4.4 m at 125 kyr BP. Retreat of the Antarctic ice sheet at the onset of the LIG is mainly forced by rising sea level and to a lesser extent by reduced ice shelf viscosity as the surface temperature increases. Global sea level shows a peak of 5.3 m at 124.5 kyr BP, which includes a minor contribution of 0.35 m from oceanic thermal expansion. Neither the individual contributions nor the total modelled sea-level stand show fast multi-millennial timescale variations as indicated by some reconstructions.

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 The Mathematical Model of Ice Sheets and the Calculation of the Evolution of the Greenland Ice Sheet

1985 ◽  
Vol 31 (109) ◽  
pp. 281-292 ◽  
Author(s):  
S.S Grigoryan ◽  
S.A Buyanov ◽  
M.S Krass ◽  
P.A Shumskiy
Keyword(s):  
Mathematical Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Numerical Data ◽  
Climatic Conditions ◽  
The Mathematical Model

AbstractAn evolutionary mathematical model of ice sheets is presented. The model takes into account the basic climatic and geophysical parameters, with temperature parameterization. Some numerical data derived from experiments on the Greenland ice sheet are received. At present the Greenland ice sheet is found to be in a state essentially different from a stationary one corresponding to modern climatic conditions.

scholarly journals Applied Glacier Research for Planning Hydro-Electric Power, Ilulissat/Jakobshavn, West Greenland

1989 ◽  
Vol 13 ◽  
pp. 257-261 ◽  
Author(s):  
H.H. Thomsen ◽  
L. Thorning ◽  
O.B. Olesen
Keyword(s):  
Electric Power ◽  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
Hot Water ◽  
Electric Power Station ◽  
Water Drainage ◽  
Drainage Pattern ◽  
Drainage Basins ◽  
Model Calculations ◽  
Radio Echo Sounding

Glaciological investigations were carried out on the Greenland ice sheet to help develop plans for a hydro-electric power station to supply energy to Ilulissat/Jakobshavn. The investigations required research on supraglacial and subglacial melt-water drainage in order to delineate water-drainage basins. This involved repeated detailed photogrammetric mapping, radio echo-sounding, hot-water drilling, and mathematical modelling of subglacial drainage. Repeated mappings combine to show an overall stability in the supraglacial drainage pattern, while model calculations for the subglacial conditions show a limited sensitivity in the predicted drainage areas to changes in hydraulic conditions. The investigations provide the basis for setting safer limits for planning hydro-electric power in the area, and give a general understanding of glacier hydrology for a continuous ice cover such as the Greenland ice sheet.

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.

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