scholarly journals A three-dimensional calving model: numerical experiments on Johnsons Glacier, Livingston Island, Antarctica

2010 ◽  
Vol 56 (196) ◽  
pp. 200-214 ◽  
Author(s):  
Jaime Otero ◽  
Francisco J. Navarro ◽  
Carlos Martin ◽  
Maria L. Cuadrado ◽  
Maria I. Corcuera
Keyword(s):  
Three Dimensional ◽  
Ice Sheets ◽  
Prognostic Models ◽  
Current Position ◽  
Polar Ice ◽  
Ice Dynamics ◽  
Ice Shelves ◽  
Tidewater Glaciers ◽  
Livingston Island ◽  
Polar Ice Sheets

AbstractCalving from tidewater glaciers and ice shelves accounts for around half the mass loss from both polar ice sheets, yet the process is not well represented in prognostic models of ice dynamics. Benn and others proposed a calving criterion appropriate for both grounded and floating glacier tongues or ice shelves, based on the penetration depth of transverse crevasses near the calving front, computed using Nye’s formula. The criterion is readily incorporated into glacier and ice-sheet models, but has not been fully validated with observations. We apply a three-dimensional extension of Benn and others’ criterion, incorporated into a full-Stokes model of glacier dynamics, to estimate the current position of the calving front of Johnsons Glacier, Antarctica. We find that two improvements to the original model are necessary to accurately reproduce the observed calving front: (1) computation of the tensile deviatoric stress opening the crevasse using the full-stress solution and (2) consideration of such a tensile stress as a function of depth. Our modelling results also suggest that Johnsons Glacier has a polythermal structure, rather than the temperate structure suggested by earlier studies.

Development of a Vertically Stabilized Thermal Probe for Studies in and Below Ice Sheets

1970 ◽  
Vol 92 (2) ◽  
pp. 263-268 ◽  
Author(s):  
H. W. C. Aamot
Keyword(s):  
Ice Sheets ◽  
Heat Transfer Analysis ◽  
Polar Ice ◽  
Thermal Probe ◽  
Ice Shelves ◽  
Polar Ice Sheets ◽  
Remote Measurements ◽  
Vertical Probe ◽  
Melt Penetration ◽  
The Antarctic

The pendulum probe is described. It is an instrumented device that penetrates polar ice sheets for remote measurements of geophysical parameters. It can only move downward by melt penetration; its instrumentation is permanently installed, sealed in the ice. The power requirements and operating costs are derived from the heat transfer analysis. The pendulum steering principle, which assures a vertical probe attitude and course, also explains its performance flexibility. The results from the first trials verify the probe’s feasibility and supply additional design information. The probe offers a unique opportunity for access to, and study of, the Antarctic Ocean waters under the Ross and Filchner ice shelves.

Shallow-Layers-Detection Ice Sounding Radar for Mapping of Polar Ice Sheets

2021 ◽  
pp. 1-10
Author(s):  
Bo Zhao ◽  
Yueyi Zhang ◽  
Shinan Lang ◽  
Yan Liu ◽  
Feng Zhang ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Polar Ice ◽  
Polar Ice Sheets

scholarly journals The response of fabric variations to simple shear and migration recrystallization

2015 ◽  
Vol 61 (227) ◽  
pp. 537-550 ◽  
Author(s):  
Joseph H. Kennedy ◽  
Erin C. Pettit
Keyword(s):  
Thermal Activation ◽  
Nearest Neighbor ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Polar Ice ◽  
Climatic Variations ◽  
Fabric Evolution ◽  
Polar Ice Sheets ◽  
Low Levels ◽  
And Migration

AbstractThe observable microstructures in ice are the result of many dynamic and competing processes. These processes are influenced by climate variables in the firn. Layers deposited in different climate regimes may show variations in fabric which can persist deep into the ice sheet; fabric may ‘remember’ these past climate regimes. We model the evolution of fabric variations below the firn–ice transition and show that the addition of shear to compressive-stress regimes preserves the modeled fabric variations longer than compression-only regimes, because shear drives a positive feedback between crystal rotation and deformation. Even without shear, the modeled ice retains memory of the fabric variation for 200 ka in typical polar ice-sheet conditions. Our model shows that temperature affects how long the fabric variation is preserved, but only affects the strain-integrated fabric evolution profile when comparing results straddling the thermal-activation-energy threshold (∼−10°C). Even at high temperatures, migration recrystallization does not eliminate the modeled fabric’s memory under most conditions. High levels of nearest-neighbor interactions will, however, eliminate the modeled fabric’s memory more quickly than low levels of nearest-neighbor interactions. Ultimately, our model predicts that fabrics will retain memory of past climatic variations when subject to a wide variety of conditions found in polar ice sheets.

scholarly journals Marine Ice Sheet Instability and Ice Shelf Buttressing Influenced Deglaciation of the Minch Ice Stream, Northwest Scotland

2018 ◽  
Author(s):  
Niall Gandy ◽  
Lauren J. Gregoire ◽  
Jeremy C. Ely ◽  
Christopher D. Clark ◽  
David M. Hodgson ◽  
...  
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Last Deglaciation ◽  
Ice Shelf ◽  
Dynamical Processes ◽  
Ice Dynamics ◽  
Surface Mass ◽  
Ice Shelves ◽  
Ice Stream ◽  
The Last Deglaciation

Abstract. Uncertainties in future sea level projections are dominated by our limited understanding of the dynamical processes that control instabilities of marine ice sheets. A valuable case to examine these processes is the last deglaciation of the British-Irish Ice Sheet. The Minch Ice Stream, which drained a large proportion of ice from the northwest sector of the British-Irish Ice Sheet during the last deglaciation, is well constrained, with abundant empirical data which could be used to inform, validate and analyse numerical ice sheet simulations. We use BISICLES, a higher-order ice sheet model, to examine the dynamical processes that controlled the retreat of the Minch Ice Stream. We simulate retreat from the shelf edge under constant "warm" surface mass balance and subshelf melt, to isolate the role of internal ice dynamics from external forcings. The model simulates a slowdown of retreat as the ice stream becomes laterally confined at a "pinning-point" between mainland Scotland and the Isle of Lewis. At this stage, the presence of ice shelves became a major control on deglaciation, providing buttressing to upstream ice. Subsequently, the presence of a reverse slope inside the Minch Strait produces an acceleration in retreat, leading to a "collapsed" state, even when the climate returns to the initial "cold" conditions. Our simulations demonstrate the importance of the Marine Ice Sheet Instability and ice shelf buttressing during the deglaciation of parts of the British-Irish Ice Sheet. Thus, geological data could be used to constrain these processes in ice sheet models used for projecting the future of our contemporary ice sheets.

New Space Observation of the Global Cryosphere

2021 ◽  
Author(s):  
Zhitong Yu ◽  
Luojia Hu ◽  
Yan Huang ◽  
Rong Ma ◽  
Peng Xiao ◽  
...  
Keyword(s):  
Sea Ice ◽  
Sea Level ◽  
Rapid Change ◽  
Ice Sheets ◽  
Dynamic Monitoring ◽  
Observation System ◽  
Polar Ice ◽  
Polar Ice Sheets ◽  
New Space ◽  
Wide Swath

<p>Quantifying changes in Earth’s ice sheets and identifying the climate drivers are central to improving sea level projections. But it is a pity that the future sea level is difficult to predicted. Space observation can provide global multiscale long-term continuous monitoring data. And it is very important for understanding intrinsic mechanisms, improve models and projections and analyze the impacts on human civilization.</p><p>Several satellites are applied for Global Cryosphere Watch, including sea ice extent and concentration, ice sheet elevation, glacier area and velocity. Although there are many variable can be measured by satellite sensors. But several variables need to improve the observing capability and developing new methods. Such as snow depth on ice, ice sheets thickness, and permafrost parameters. China has established high-resolution earth observation system to realize stereopsis and dynamic monitoring of the lands, the oceans and the atmosphere.</p><p>Currently, Qian Xuesen Laboratory working together with Sun Yat-sen University, is trying to design a new space observation system to support Three Poles Environment and Climate Changes project. We are conceptualizing two series satellites including FluxSats and BingSats for carbon/water cycle and cryosphere observations, respectively. To clarify the mechanism of the cryosphere carbon release and carbon sink effects of the oceans and ecosystems. We are developing a new lidar system for detecting the concentration and wind speed, and then atmospheric boundary layer flux exchange can be estimated. To understand the rapid change of the sea ice, such as drift, fragmentation and freeze. We need a short revisit and wide swath system capabilities. InSAR technology gives the digitial elevation of the ice surface. And temporal difference InSAR (DInSAR) shows the changes of elevation. BingSAT-Tomographic Observation of Polar Ice Sheets (TOPIS) achieves the tomographic observation of polar ice sheets with a wide swath and short revisit time. Over the polar regions, the CubeSats form a large cross-track baseline with the master satellite to realize the high two-dimensional spatial resolution with the along-track synthetic aperture. The MirrorSAR technology is utilized in BingSat-TOPIS to achieve time and phase synchronization more economically than the traditional bistatic radar. Sparse array and digital beamforming are also considered to significantly reduce the number of microsatellites, and achieve tomographic images of polar ice sheets.</p>

Modeling the Interconnectivity of Non-stationary Polar Ice Sheets

2021 ◽  
Author(s):  
Luke Jackson ◽  
Katarina Juselius ◽  
Andrew Martinez ◽  
Felix Pretis
Keyword(s):  
Ice Sheets ◽  
Polar Ice ◽  
Polar Ice Sheets

scholarly journals Layer echoes in polar ice sheets

1975 ◽  
Vol 15 (73) ◽  
pp. 95-101 ◽  
Author(s):  
Gudmandsen Preben
Keyword(s):  
Stable Isotope ◽  
Ice Sheets ◽  
Polar Ice ◽  
Last Glaciation ◽  
Polar Ice Sheets ◽  
Isotope Profile

AbstractA multitude of extensive layers have been observed by radio-echo soundings in Greenland. By comparison with the stable isotope profile from Camp Century it is found that layering in the lop of the ice has been formed in the period since the last glaciation. Radio-echo layers observed at greater depths in central Greenland may have been created in the period of the interstadials and further down possibly in the period prior to the last glaciation. Further investigations are needed to prove this.

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