scholarly journals Results From The Amery Ice Shelf Project

1982 ◽  
Vol 3 ◽  
pp. 36-41 ◽  
Author(s):  
W. F. Budd ◽  
M. J. Corry ◽  
T. H. Jacka
Keyword(s):  
High Strain ◽  
Ice Core ◽  
Snow Accumulation ◽  
Ice Thickness ◽  
Surface Slope ◽  
Ice Shelf ◽  
Substantial Growth ◽  
Basal Ice ◽  
Amery Ice Shelf ◽  
Comprehensive Study

The major results from a comprehensive study of the Amery Ice Shelf are presented, following the work of a wintering expedition in 1968 and supplemented by further measurements during the summer seasons of 1969 to 1971. The Programme included ice-core drilling, oversnow surveys for ice movement and optical levelling, ice-thickness sounding, and measurements of snow accumulation. The new data obtained provide the basis for a more accurate assessment of the mass balance and dynamics of the ice shelf than was possible from the earlier surveys.The results indicate a substantial growth of basal ice under the ice shelf inland where the ice thickness is greater than 450 m. Further towards the ice front the high strain thinning is approximately balanced by the horizontal ice advection.The velocity distribution over the ice shelf is primarily governed by a substantial surface slope towards the ice front and high restraining shear stress along the sides.

scholarly journals Results From The Amery Ice Shelf Project

1982 ◽  
Vol 3 ◽  
pp. 36-41 ◽  
Author(s):  
W. F. Budd ◽  
M. J. Corry ◽  
T. H. Jacka
Keyword(s):  
High Strain ◽  
Ice Core ◽  
Snow Accumulation ◽  
Ice Thickness ◽  
Surface Slope ◽  
Ice Shelf ◽  
Substantial Growth ◽  
Basal Ice ◽  
Amery Ice Shelf ◽  
Comprehensive Study

The major results from a comprehensive study of the Amery Ice Shelf are presented, following the work of a wintering expedition in 1968 and supplemented by further measurements during the summer seasons of 1969 to 1971. The Programme included ice-core drilling, oversnow surveys for ice movement and optical levelling, ice-thickness sounding, and measurements of snow accumulation. The new data obtained provide the basis for a more accurate assessment of the mass balance and dynamics of the ice shelf than was possible from the earlier surveys. The results indicate a substantial growth of basal ice under the ice shelf inland where the ice thickness is greater than 450 m. Further towards the ice front the high strain thinning is approximately balanced by the horizontal ice advection. The velocity distribution over the ice shelf is primarily governed by a substantial surface slope towards the ice front and high restraining shear stress along the sides.

scholarly journals Numerical Models of Steady-State Thickness and Basal Ice Configurations of the Central Ronne Ice Shelf, Antarctica

1988 ◽  
Vol 11 ◽  
pp. 64-70 ◽  
Author(s):  
M. A. Lange ◽  
D. R. MacAyeal
Keyword(s):  
Numerical Models ◽  
Accumulation Rate ◽  
Basal Layer ◽  
Snow Accumulation ◽  
Time Dependent ◽  
Ice Thickness ◽  
Residence Times ◽  
Ice Shelf ◽  
Basal Ice ◽  
Two Factors

Radar ice-thickness surveys and bore-hole measurements suggest that the central part of Ronne Ice Shelf possesses a lobe-shaped basal layer of undetermined nature (probably saline ice). This layer is characterized by high radio-wave absorbtivity and by thicknesses up to approximately 300 m. We reconstruct this basal layer and the associated ice-shelf thickness and flow distributions, using a time-dependent ice-shelf model forced with prescribed basal freezing rates. Characteristics of the basal layer are controlled by two factors: (i) long ice-column residence times in the unventilated pocket between Henry and Korff ice rises and Doake Ice Rumples, and (ii) basal freezing rates in this pocket that exceed the snow-accumulation rate (currently averaging 0.35 m/a ice equivalent across the ice shelf).

scholarly journals Numerical Models of Steady-State Thickness and Basal Ice Configurations of the Central Ronne Ice Shelf, Antarctica

1988 ◽  
Vol 11 ◽  
pp. 64-70 ◽  
Author(s):  
M. A. Lange ◽  
D. R. MacAyeal
Keyword(s):  
Numerical Models ◽  
Accumulation Rate ◽  
Basal Layer ◽  
Snow Accumulation ◽  
Time Dependent ◽  
Ice Thickness ◽  
Residence Times ◽  
Ice Shelf ◽  
Basal Ice ◽  
Two Factors

Radar ice-thickness surveys and bore-hole measurements suggest that the central part of Ronne Ice Shelf possesses a lobe-shaped basal layer of undetermined nature (probably saline ice). This layer is characterized by high radio-wave absorbtivity and by thicknesses up to approximately 300 m. We reconstruct this basal layer and the associated ice-shelf thickness and flow distributions, using a time-dependent ice-shelf model forced with prescribed basal freezing rates. Characteristics of the basal layer are controlled by two factors: (i) long ice-column residence times in the unventilated pocket between Henry and Korff ice rises and Doake Ice Rumples, and (ii) basal freezing rates in this pocket that exceed the snow-accumulation rate (currently averaging 0.35 m/a ice equivalent across the ice shelf).

scholarly journals Radio-echo sounding of the lambert glacier basin

1975 ◽  
Vol 15 (73) ◽  
pp. 103-111 ◽  
Author(s):  
V. I. Morgan ◽  
W. F. Budd
Keyword(s):  
Surface Topography ◽  
Sea Level ◽  
Drainage Basin ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Deep Trench ◽  
Glacier System ◽  
Amery Ice Shelf ◽  
Lambert Glacier ◽  
Echo Sounding

AbstractSeveral seasons of aerial ice-thickness soundings over the region of the Prince Charles Mountains, the Lambert Glacier system, the Amery Ice Shelf, and their drainage basin in east Antarctica have now been completed. The measurements provide detailed maps of surface topography and ice thickness over an area of about 2 X 105 km2. The equipment used consisted of a 100 MHz echo sounder designed and constructed by Antarctic Division and carried in a Pilatus Porter aircraft. ERTS imagery provides a valuable background for portraying the echo-sounding results. These results show that an extensive, deep subglacial valley system forms the basis of the large drainage basin with concave ice surface topography which channels the ice flow into the Amery Ice Shelf. Deep glacial streams penetrate a long way into the ice-sheet basin. The rock relief is considerable, varying from 3 000 m above (present) sea-level to 2 000 m below sea-level. A very deep subglacial trench exists in the region of the confluence of the Fisher, Mellor, and Lambert Glaciers where the ice thickness reaches 2 500 m. The low surface slope and high ice velocity are suggestive of high melt production in this region. The strong echo, together with the high bedrock back-slope, suggests that the deep trench may contain a basal melt lake.

scholarly journals Geometry and ice dynamics of the Darwin–Hatherton glacial system, Transantarctic Mountains

2017 ◽  
Vol 63 (242) ◽  
pp. 959-972
Author(s):  
METTE K. GILLESPIE ◽  
WENDY LAWSON ◽  
WOLFGANG RACK ◽  
BRIAN ANDERSON ◽  
DONALD D. BLANKENSHIP ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ice Dynamics ◽  
Ross Ice Shelf ◽  
Basal Ice ◽  
Grounding Line ◽  
Ice Flows ◽  
Ice Velocity ◽  
The Mean

ABSTRACTThe Darwin–Hatherton Glacial system (DHGS) connects the East Antarctic Ice Sheet (EAIS) with the Ross Ice Shelf and is a key area for understanding past variations in ice thickness of surrounding ice masses. Here we present the first detailed measurements of ice thickness and grounding zone characteristics of the DHGS as well as new measurements of ice velocity. The results illustrate the changes that occur in glacier geometry and ice flux as ice flows from the polar plateau and into the Ross Ice Shelf. The ice discharge and the mean basal ice shelf melt for the first 8.5 km downstream of the grounding line amount to 0.24 ± 0.05 km3 a−1 and 0.3 ± 0.1 m a−1, respectively. As the ice begins to float, ice thickness decreases rapidly and basal terraces develop. Constructed maps of glacier geometry suggest that ice drainage from the EAIS into the Darwin Glacier occurs primarily through a deep subglacial canyon. By contrast, ice thins to <200 m at the head of the much slower flowing Hatherton Glacier. The glaciological field study establishes an improved basis for the interpretation of glacial drift sheets at the link between the EAIS and the Ross Ice Sheet.

scholarly journals Investigation of the 18O Content of a 100 m Ice Core From the Ronne Ice Shelf, Antarctica

1988 ◽  
Vol 10 ◽  
pp. 43-47 ◽  
Author(s):  
W. Graf ◽  
O. Reinwarth ◽  
H. Moser ◽  
W. Stichler
Keyword(s):  
Flow Model ◽  
Accumulation Rate ◽  
Ice Core ◽  
Snow Accumulation ◽  
Two Dimensional ◽  
Ice Shelf ◽  
Short Term ◽  
The Core ◽  
Two Dimensional Flow ◽  
Field Season

A 100 m ice core from the Ronne Ice Shelf, drilled during the 1983-84 field season, was dated by isotopic stratigraphy, using the well-known seasonal variation in the 18O content in firn and ice; the layers at a depth of 89 m are probably 400 years old. Layer thicknesses deduced from the 18O profile indicate short-term variations of the snow-accumulation rate over the last 400 years. The area of deposition of the material recovered with the core is estimated by a two-dimensional flow model and by the 18O content of the core, which decreases from –27.5‰ in the upper part of the core to –32.0‰ at 89 m depth.

scholarly journals Thinning and Grounding-Line Retreat on Ross Ice Shelf, Antarctica

1988 ◽  
Vol 11 ◽  
pp. 165-172 ◽  
Author(s):  
R. H. Thomas ◽  
S. N. Stephenson ◽  
R. A. Bindschadler ◽  
S. Shabtaie ◽  
C. R. Bentley
Keyword(s):  
Snow Accumulation ◽  
Gravity Potential ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Ross Ice Shelf ◽  
Major Activity ◽  
Ice Stream ◽  
Grounding Line ◽  
Ice Stream B ◽  
Basal Melting

Detailed measurements of surface topography, ice motion, snow accumulation, and ice thickness were made in January 1974 and again in December 1984, along an 8 km stake network extending from the ice sheet, across the grounding line, and on to floating ice shelf in the mouth of slow-moving Ice Stream C, which flows into the eastern side of Ross Ice Shelf, Antarctica. During the 11 years between surveys, the grounding line retreated by approximately 300 m. This was caused by net thinning of the ice shelf, which we believe to be a response to the comparatively recent, major decrease in ice discharge from Ice Stream C. Farther inland, snow accumulation is not balanced by ice discharge, and the ice stream is growing progressively thicker.There is evidence that the adjacent Ice Stream B has slowed significantly over the last decade, and this may be an early indication that this fast-moving ice stream is about to enter a period of stagnation similar to that of Ice Stream C. Indeed, these large ice streams flowing from West Antarctica into Ross Ice Shelf may oscillate between periods of relative stagnation and major activity. During active periods, large areas of ice shelf thicken and run aground on seabed to form extensive “ice plains” in the mouth of the ice stream. Ultimately, these become too large to be pushed seaward by the ice stream, which then slows down and enters a period of stagnation. During this period, the grounding line of the ice plain retreats, as we observe today in the mouth of Ice Stream C, because nearby ice shelf, no longer compressed by ice-stream motion, progressively thins. At the same time, water within the deformable till beneath the ice starts to freeze on to the base of the ice stream, and snow accumulation progressively increases the ice thickness. A new phase of activity would be initiated when the increasing gravity potential of the ice stream exceeds the total resistance of the shrinking ice plain and the thinning layer of deformable till at the bed. This could occur rapidly if the effects of the shrinking ice plain outweigh those of the thinning (and therefore stiffening) till. Otherwise, the till layer would finally become completely frozen, and the ice stream would have to thicken sufficiently to initiate significant heating by internal deformation, followed by basal melting and finally saturation of an adequate thickness of till; this could take some thousands of years.

scholarly journals Ice thickness over the southern limit of the Amery Ice Shelf, East Antarctica, and reassessment of the mass balance of the central portion of the Lambert Glacier-Amery Ice Shelf system

2014 ◽  
Vol 55 (66) ◽  
pp. 81-86 ◽  
Author(s):  
Jiahong Wen ◽  
Long Huang ◽  
Weili Wang ◽  
T.H. Jacka ◽  
V. Damm ◽  
...  
Keyword(s):  
Mass Balance ◽  
Atmospheric Modeling ◽  
East Antarctica ◽  
Central Portion ◽  
Ice Thickness ◽  
Ice Shelf ◽  
Southern Limit ◽  
Surface Mass ◽  
Amery Ice Shelf ◽  
Lambert Glacier

AbstractWe combine radio-echo sounding ice thickness data from the BEDMAP Project database and the PCMEGA (Prince Charles Mountains Expedition of Germany and Australia) dataset to generate a new ice thickness grid for the southern limit region of the Amery Ice Shelf, East Antarctica. We then reassess the mass balance of the central portion of the Lambert-Amery system, incorporating flow information derived from synthetic aperture radar interferometry (InSAR) and a modeled surface mass-balance dataset based on regional atmospheric modeling. Our analysis reveals that Mellor and Fisher Glaciers are approximately in balance to the level of our measurement uncertainty, while Lambert Glacier has a positive imbalance of 4.2 ±2.3 Gta1. The mass budget for the whole Lambert Glacier basin is approximately in balance, and the average basal melt rate in the downstream section of the ice shelf is 5.1 ± 3.0 m a-1. Our results differ substantially from other recent estimates using hydrostatically derived ice thickness data.

scholarly journals Topographic control of regional accumulation rate variability at South Pole and implications for ice-core interpretation

2004 ◽  
Vol 39 ◽  
pp. 214-218 ◽  
Author(s):  
Gordon S. Hamilton
Keyword(s):  
Accumulation Rate ◽  
Ice Core ◽  
Ice Sheet ◽  
Ice Cores ◽  
Snow Accumulation ◽  
Topographic Effects ◽  
South Pole ◽  
Accumulation Rates ◽  
Surface Slope ◽  
Ice Dynamics

AbstractSnow-accumulation rates are known to be sensitive to local changes in ice-sheet surface slope because of the effect of katabatic winds. These topographic effects can be preserved in ice cores that are collected at non-ice-divide locations. The trajectory of an ice-core site at South Pole is reconstructed using measurements of ice-sheet motion to show that snow was probably deposited at places of different surface slope during the past 1000 years. Recent accumulation rates, derived from shallow firn cores, vary along this trajectory according to surface topography, so that on a relatively steep flank mean annual accumulation is ∼18% smaller than on a nearby topographic depression. These modern accumulation rates are used to reinterpret the cause of accumulation rate variability with time in the long ice-core record as an ice-dynamics effect and not a climate-change signal. The results highlight the importance of conducting ancillary ice-dynamics measurements as part of ice-coring programs so that topographic effects can be deconvolved from potential climate signals.

scholarly journals A comparative study of changes in the Lambert Glacier/Amery Ice Shelf system, East Antarctica, during 2004–2008 using gravity and surface elevation observations

2016 ◽  
Vol 62 (235) ◽  
pp. 888-904 ◽  
Author(s):  
HUAN XIE ◽  
RONGXING LI ◽  
XIAOHUA TONG ◽  
XIAOLEI JU ◽  
JUN LIU ◽  
...  
Keyword(s):  
Comparative Study ◽  
Flow Speed ◽  
Snow Accumulation ◽  
Mass Change ◽  
Spatial Density ◽  
Positive Trend ◽  
Positive Mass ◽  
Ice Shelf ◽  
Amery Ice Shelf ◽  
Lambert Glacier

ABSTRACTWe present results of a regional comparative study of surface mass changes from 2004 to 2008 based on Gravity Recovery and Climate Experiment (GRACE), The Ice, Cloud and Land Elevation Satellite (ICESat) and CHINARE observations over the Lambert Glacier/Amery Ice Shelf system (LAS). Estimation of the ICESat mass change rates benefitted from the density measurements along the CHINARE traverse and a spatial density adjustment method for reducing the effect of spatial density variations. In the high-elevation inland region, a positive trend was estimated from both ICESat and GRACE data, which is in line with the CHINARE accumulation measurements. In the coastal region, there were areas with high level accumulations in both ICESat and GRACE trend maps. In many high flow-speed glacier areas, negative mass change rates may be caused by dynamic ice flow discharges that have surpassed the snow accumulation. Overall, the mass change rate estimate in the LAS of 2004–2008 from the GRACE, ICESat and CHINARE data is 5.41 ± 4.59 Gt a−1, indicating a balanced to slightly positive mass trend. Along with other published results, this suggests that a longer-term positive mass trend in the LAS may have slowed in recent years.

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