scholarly journals Vlf Surface-impedance Measurements for Ice-defth Mapping in the Antarctic

1989 ◽  
Vol 35 (120) ◽  
pp. 197-200 ◽  
Author(s):  
David V. Thiel ◽  
Fiona Neall
Keyword(s):  
Surface Impedance ◽  
Computer Modelling ◽  
Ice Sheet ◽  
Impedance Measurements ◽  
Depth Data ◽  
Impedance Data ◽  
Single Person ◽  
The Antarctic ◽  
Ice Radar ◽  
Data Surface

Abstract VLF surface-impedance measurements were made along four traverses on the Antarctic ice sheet in the vicinity of Casey base. Computer modelling of the surface-impedance data allowed ice-depth predictions to be made; predictions which are almost independent of ice temperature for ice depths less than 800 m. Results agree with ice-radar and other ice-depth data. Surface-impedance anomalies were observed close to moraines and crevasses in the ice sheet. The technique is fast and the instrumentation sufficiently portable for single-person operation.

scholarly journals Evidence Against and Factors Preventing Major Surges of the Antarctic Ice Sheet

1979 ◽  
Vol 24 (90) ◽  
pp. 485-487 ◽  
Author(s):  
G. de Q. Robin
Keyword(s):  
Steady State ◽  
Computer Modelling ◽  
Ice Sheet ◽  
List Type ◽  
Flow Lines ◽  
Antarctic Ice Sheet ◽  
Depth Profiles ◽  
The Past ◽  
The Antarctic ◽  
Temperature Depth

Abstract Although computer modelling using realistic flow parameters can simulate surging of the Antarctic ice sheet, the present model does not take into account certain factors that make surging less probable. Before discussing these factors, knowledge of the Antarctic ice sheet that might indicate the occurrence of former surging is reviewed. The following studies appear relevant (a) Observed temperature–depth profiles approximate to steady-state solutions, whereas a major surge within the last 10 000 to 20000 years would have produced markedly different temperature–depth profiles at Byrd and Vostok Stations. (b) Isotopic profiles are estimated for steady-state and for surging behaviour of the Antarctic ice sheet. When these are compared with observed profiles no convincing evidence of surging over the past 10 000 to 50 000 years is seen. (c) Studies of flow lines in and around the Ross Ice Shelf do not reveal any surging of discharge glaciers in the past I 000 to 2 000 years. (d) Although mass-balance calculations and balance-velocity calculations on the Antarctic ice sheet are not accurate, ice discharge is generally estimated to be within a factor of two of the total mass accumulation. Three stabilizing factors that have not been included in computer models and need consideration are (1) It appears unlikely that a surge will be propagated up-stream of any substantial bedrock slope that opposes the ice motion. (2) The very high effective viscosity of great thicknesses of ice at very low temperatures adds considerable rigidity to the ice sheet at the lateral boundaries of any incipient surge. (3) Strong convergence of flow lines towards ice streams and major trunk glaciers apparently provides a stabilizing factor.

scholarly journals Evidence Against and Factors Preventing Major Surges of the Antarctic Ice Sheet

1979 ◽  
Vol 24 (90) ◽  
pp. 485-487
Author(s):  
G. de Q. Robin
Keyword(s):  
Steady State ◽  
Computer Modelling ◽  
Ice Sheet ◽  
List Type ◽  
Flow Lines ◽  
Antarctic Ice Sheet ◽  
Depth Profiles ◽  
The Past ◽  
The Antarctic ◽  
Temperature Depth

AbstractAlthough computer modelling using realistic flow parameters can simulate surging of the Antarctic ice sheet, the present model does not take into account certain factors that make surging less probable. Before discussing these factors, knowledge of the Antarctic ice sheet that might indicate the occurrence of former surging is reviewed. The following studies appear relevant (a)Observed temperature–depth profiles approximate to steady-state solutions, whereas a major surge within the last 10 000 to 20000 years would have produced markedly different temperature–depth profiles at Byrd and Vostok Stations.(b)Isotopic profiles are estimated for steady-state and for surging behaviour of the Antarctic ice sheet. When these are compared with observed profiles no convincing evidence of surging over the past 10 000 to 50 000 years is seen.(c)Studies of flow lines in and around the Ross Ice Shelf do not reveal any surging of discharge glaciers in the past I 000 to 2 000 years.(d)Although mass-balance calculations and balance-velocity calculations on the Antarctic ice sheet are not accurate, ice discharge is generally estimated to be within a factor of two of the total mass accumulation.Three stabilizing factors that have not been included in computer models and need consideration are (1)It appears unlikely that a surge will be propagated up-stream of any substantial bedrock slope that opposes the ice motion.(2)The very high effective viscosity of great thicknesses of ice at very low temperatures adds considerable rigidity to the ice sheet at the lateral boundaries of any incipient surge.(3)Strong convergence of flow lines towards ice streams and major trunk glaciers apparently provides a stabilizing factor.

scholarly journals Complex Principal Component Analysis of Antarctic Ice Sheet Mass Balance

2021 ◽  
Vol 13 (3) ◽  
pp. 480
Author(s):  
Jingang Zhan ◽  
Hongling Shi ◽  
Yong Wang ◽  
Yixin Yao
Keyword(s):  
Principal Component Analysis ◽  
Ice Sheet ◽  
Low Frequency ◽  
Principal Component ◽  
Equatorial Pacific ◽  
Mass Change ◽  
Frequency Variation ◽  
Periodic Signal ◽  
Time Frequency ◽  
The Antarctic

Ice sheet changes of the Antarctic are the result of interactions among the ocean, atmosphere, and ice sheet. Studying the ice sheet mass variations helps us to understand the possible reasons for these changes. We used 164 months of Gravity Recovery and Climate Experiment (GRACE) satellite time-varying solutions to study the principal components (PCs) of the Antarctic ice sheet mass change and their time-frequency variation. This assessment was based on complex principal component analysis (CPCA) and the wavelet amplitude-period spectrum (WAPS) method to study the PCs and their time-frequency information. The CPCA results revealed the PCs that affect the ice sheet balance, and the wavelet analysis exposed the time-frequency variation of the quasi-periodic signal in each component. The results show that the first PC, which has a linear term and low-frequency signals with periods greater than five years, dominates the variation trend of ice sheet in the Antarctic. The ratio of its variance to the total variance shows that the first PC explains 83.73% of the mass change in the ice sheet. Similar low-frequency signals are also found in the meridional wind at 700 hPa in the South Pacific and the sea surface temperature anomaly (SSTA) in the equatorial Pacific, with the correlation between the low-frequency periodic signal of SSTA in the equatorial Pacific and the first PC of the ice sheet mass change in Antarctica found to be 0.73. The phase signals in the mass change of West Antarctica indicate the upstream propagation of mass loss information over time from the ocean–ice interface to the southward upslope, which mainly reflects ocean-driven factors such as enhanced ice–ocean interaction and the intrusion of warm saline water into the cavities under ice shelves associated with ice sheets which sit on retrograde slopes. Meanwhile, the phase signals in the mass change of East Antarctica indicate the downstream propagation of mass increase information from the South Pole toward Dronning Maud Land, which mainly reflects atmospheric factors such as precipitation accumulation.

scholarly journals A Joint Inversion Estimate of Antarctic Ice Sheet Mass Balance Using Multi-Geodetic Data Sets

2019 ◽  
Vol 11 (6) ◽  
pp. 653 ◽  
Author(s):  
Chunchun Gao ◽  
Yang Lu ◽  
Zizhan Zhang ◽  
Hongling Shi
Keyword(s):  
Mass Balance ◽  
Joint Inversion ◽  
Ice Sheet ◽  
Mass Change ◽  
West Antarctica ◽  
Amundsen Sea ◽  
Antarctic Ice Sheet ◽  
Forward Models ◽  
Uplift Rates ◽  
The Antarctic

Many recent mass balance estimates using the Gravity Recovery and Climate Experiment (GRACE) and satellite altimetry (including two kinds of sensors of radar and laser) show that the ice mass of the Antarctic ice sheet (AIS) is in overall decline. However, there are still large differences among previously published estimates of the total mass change, even in the same observed periods. The considerable error sources mainly arise from the forward models (e.g., glacial isostatic adjustment [GIA] and firn compaction) that may be uncertain but indispensable to simulate some processes not directly measured or obtained by these observations. To minimize the use of these forward models, we estimate the mass change of ice sheet and present-day GIA using multi-geodetic observations, including GRACE and Ice, Cloud and land Elevation Satellite (ICESat), as well as Global Positioning System (GPS), by an improved method of joint inversion estimate (JIE), which enables us to solve simultaneously for the Antarctic GIA and ice mass trends. The GIA uplift rates generated from our JIE method show a good agreement with the elastic-corrected GPS uplift rates, and the total GIA-induced mass change estimate for the AIS is 54 ± 27 Gt/yr, which is in line with many recent GPS calibrated GIA estimates. Our GIA result displays the presence of significant uplift rates in the Amundsen Sea Embayment of West Antarctica, where strong uplift has been observed by GPS. Over the period February 2003 to October 2009, the entire AIS changed in mass by −84 ± 31 Gt/yr (West Antarctica: −69 ± 24, East Antarctica: 12 ± 16 and the Antarctic Peninsula: −27 ± 8), greater than the GRACE-only estimates obtained from three Mascon solutions (CSR: −50 ± 30, JPL: −71 ± 30, and GSFC: −51 ± 33 Gt/yr) for the same period. This may imply that single GRACE data tend to underestimate ice mass loss due to the signal leakage and attenuation errors of ice discharge are often worse than that of surface mass balance over the AIS.

scholarly journals Glaciological and Geomorphological Reconnaissance in the Antarctic in 1956

1957 ◽  
Vol 3 (21) ◽  
pp. 54-61 ◽  
Author(s):  
P. A. Shumskiy
Keyword(s):  
Ice Sheet ◽  
Preliminary Account ◽  
Antarctic Expedition ◽  
Ice Regime ◽  
Academy Of Sciences ◽  
The Antarctic

Abstract This paper presents a preliminary account of the glaciological observations made by the Antarctic Expedition of the U.S.S.R. Academy of Sciences in Kaiser Wilhelm II Land, Queen Mary Land and Knox Coast in 1956. The topography of the edge of the ice sheet is described, and the ice regime is discussed, particularly in relation to the existence of ice-free areas such as “Bunger’s oasis”.

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