scholarly journals Modeling the Antarctic ice sheet

1997 ◽  
Vol 25 ◽  
pp. 259-268 ◽  
Author(s):  
Mikhail Verbitsky ◽  
Barry Saltzman
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Antarctic Ice Sheet ◽  
Thermodynamic Equation ◽  
Last Glacial ◽  
West Antarctic ◽  
Ice Stream ◽  
The Antarctic ◽  
The Last Glacial

A three-dimensional (3-D), high-resolution, non-linearly viscous, non-isothermal ice-sheet model is employed to calculate the “present-day” equilibrium regime of the Antarctic ice sheet and its evolution during the last glacial cycle. The model is augmented by an approximate formula for ice-sheet basal temperature, based on a scaling of the thermodynamic equation for the ice flow. Steady-state solutions for both the shape and extent of the areas of basal melting (or freezing) are shown to be in good agreement with those obtained from the solution of the full 3-D thermodynamic equation. The solution for the basal temperature field of the West Antarctic Siple Coast produces areas at the pressure-melting point separated by strips of frozen-to-bed ice, the structure of which is reminiscent of Ice Streams A–E. This configuration appears to be robust, preserving its features in spite of climatic changes during the last glacial cycle. Ice Stream C seems to be more vulnerable to stagnation, switching to a passive mode at least once during the penultimate interglacial. We conjecture that the peculiarities of local topography determine the unique behavior of Ice Stream C: reduced basal stress and, consequently, relatively weak warming due to internal friction and basal sliding is not able to counteract the advective cooling during the periods of increased snowfall rate.

scholarly journals Modeling the Antarctic ice sheet

1997 ◽  
Vol 25 ◽  
pp. 259-268 ◽  
Author(s):  
Mikhail Verbitsky ◽  
Barry Saltzman
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Antarctic Ice Sheet ◽  
Thermodynamic Equation ◽  
Last Glacial ◽  
Ice Stream ◽  
Basal Melting ◽  
The Antarctic ◽  
The Last Glacial

A three-dimensional (3-D), high-resolution, non-linearly viscous, non-isothermal ice-sheet model is employed to calculate the “present-day” equilibrium regime of the Antarctic ice sheet and its evolution during the last glacial cycle. The model is augmented by an approximate formula for ice-sheet basal temperature, based on a scaling of the thermodynamic equation for the ice flow. Steady-state solutions for both the shape and extent of the areas of basal melting (or freezing) are shown to be in good agreement with those obtained from the solution of the full 3-D thermodynamic equation. The solution for the basal temperature field of the West Antaretie Siple Coast produces areas at the pressure-melting point separated by strips of frozen-to-bed ice, the structure of which is reminiscent of Ice Streams A–E. This configuration appears to be robust, preserving its features in spite of climatic changes during the last glacial cycle. Ice Stream C seems to be more vulnerable to stagnation, switching to a passive mode at least once during the penultimate interglacial. We conjecture that the peculiarities of local topography determine the unique behavior of Ice Stream C: reduced basal stress and, consequently, relatively weak warming due to internal friction and basal sliding is not able to counteract the advective cooling during the periods of increased snowfall rate.

scholarly journals A comparison of different ways of dealing with isostasy: examples from modelling the Antarctic ice sheet during the last glacial cycle

1996 ◽  
Vol 23 ◽  
pp. 309-317 ◽  
Author(s):  
Emmanuel Le Meur ◽  
Philippe Huybrechts
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Earth Model ◽  
Glacial Cycle ◽  
Complex Deformation ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
The Antarctic ◽  
Strong Control ◽  
The Last Glacial

The bedrock isostatic response exerts a strong control on ice-sheet dynamics and is therefore always taken into account in ice-sheet models. This paper reviews the various methods normally used in the ice-sheet modelling community to deal with the bedrock response and compares these with a more sophisticated full-Earth model. Each of these bedrock treatments, five in total, is coupled with a three-dimensional thermomechanical ice-sheet model under the same forcing conditions to simulate the Antarctic ice sheet during the last glacial cycle. The outputs of the simulations are compared on the basis of the time-dependent behaviour for the total ice volume and the mean bedrock elevation during the cycle and of the present rate of uplift over Antarctica. This comparison confirms the necessity of accounting for the elastic bending of the lithosphere in order to yield realistic bedrock patterns. It furthermore demonstrates the deficiencies inherent to the diffusion equation in modelling the complex deformation within the mantle. Nevertheless, when characteristic parameters are varied within their range of uncertainty, differences within one single method are often of the same order as those between the various methods. This overview finally attempts to point out the main advantages and drawbacks of each of these methods and to determine which one is most appropriate depending on the specific modelling requirements.

scholarly journals A comparison of different ways of dealing with isostasy: examples from modelling the Antarctic ice sheet during the last glacial cycle

1996 ◽  
Vol 23 ◽  
pp. 309-317 ◽  
Author(s):  
Emmanuel Le Meur ◽  
Philippe Huybrechts
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Earth Model ◽  
Glacial Cycle ◽  
Complex Deformation ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
The Antarctic ◽  
Strong Control ◽  
The Last Glacial

The bedrock isostatic response exerts a strong control on ice-sheet dynamics and is therefore always taken into account in ice-sheet models. This paper reviews the various methods normally used in the ice-sheet modelling community to deal with the bedrock response and compares these with a more sophisticated full-Earth model. Each of these bedrock treatments, five in total, is coupled with a three-dimensional thermomechanical ice-sheet model under the same forcing conditions to simulate the Antarctic ice sheet during the last glacial cycle. The outputs of the simulations are compared on the basis of the time-dependent behaviour for the total ice volume and the mean bedrock elevation during the cycle and of the present rate of uplift over Antarctica. This comparison confirms the necessity of accounting for the elastic bending of the lithosphere in order to yield realistic bedrock patterns. It furthermore demonstrates the deficiencies inherent to the diffusion equation in modelling the complex deformation within the mantle. Nevertheless, when characteristic parameters are varied within their range of uncertainty, differences within one single method are often of the same order as those between the various methods. This overview finally attempts to point out the main advantages and drawbacks of each of these methods and to determine which one is most appropriate depending on the specific modelling requirements.

The effect of the GIA feedback loop on the evolution of the Antarctic Ice sheet over the last glacial cycle using a coupled 3D GIA – Ice Dynamic model

2021 ◽  
Author(s):  
Caroline van Calcar ◽  
Bas de Boer ◽  
Bas Blank ◽  
Roderik van de Wal ◽  
Wouter van der Wal
Keyword(s):  
Feedback Loop ◽  
Ice Sheet ◽  
Line Position ◽  
Glacial Cycle ◽  
Antarctic Ice Sheet ◽  
Last Glacial ◽  
Grounding Line ◽  
The Antarctic ◽  
Lateral Variations ◽  
The Last Glacial

<p>The Earth’s surface and interior deform due to a changing load of the Antarctic Ice Sheet (AIS) during the last glacial cycle, called Glacial Isostatic Adjustment (GIA). This deformation changes the surface height of the ice sheet and indirectly the groundling line position. These changes in surface height and grounding line position influence the evolution of the AIS and consequently, again the load on the Earth’s surface. As a result, GIA operates as a negative feedback loop and could stabilize the evolution of the AIS. This feedback maybe particularly relevant for relatively low viscosities of the mantle in West Antarctica which lead to a relatively fast response time of the bedrock due to changes in the West Antarctic Ice Sheet loading. Most studies capture this process by ignoring lateral variations in the viscosity of the mantle and the stabilizing GIA feedback loop. Here we present a new method to couple an ice sheet model to a GIA model at a variable timestep in the order of a thousand years. Several experiments have been done using different radial and lateral varying rheologies for simulations of the last glacial cycle. It is shown that the effect of including lateral variations and accounting for the stabilizing GIA feedback is up to 80 kilometers for the grounding line position and 400 meters for the ice thickness. The largest differences are observed close to the grounding line of the Ronne ice shelf and at several locations in East Antarctica. The total ice volume of the AIS increases by 0.5 percent over 5000 years when including the 3D GIA feedback loops in the coupled model. These results quantify the local importance of including GIA feedback effects in ice dynamic models when simulating the Antarctic Ice Sheet evolution over the full glacial cycle.  </p>

scholarly journals The Antarctic Ice Sheet During the Last Glacial-Interglacial Cycle: A Three-Dimensional Experiment

1990 ◽  
Vol 14 ◽  
pp. 115-119 ◽  
Author(s):  
Philippe Huybrechts
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Weddell Sea ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Last Glacial ◽  
West Antarctic ◽  
The Last Glacial

A complete three-dimensional thermo-mechanical ice-shect model for the entire Antarctic ice sheet, including an ice shelf, grounding line-dynamics and isostatic bed adjustment, is employed to simulate the response of the ice sheet during the last glacial-interglacial cycle with respect to changing environmental conditions. To do this, the Vostok temperature signal is used to force changes in surface temperature and accumulation rate and sea level prescribed by a piecewise linear sawtooth function. Model calculations started at 160 ka B.P. In line with glacial geological evidence, the most pronounced fluctuations are found in the West Antarctic ice sheet and appear to be essentially controlled by changes in eustatic sea level. Grounding occurs more readily in the Weddell Sea than in the Ross Sea and, due to the long time scales involved, the ice sheet does not reach its full glacial extent until 16 ka B.p. The concomitant disintegration of the West Antarctic ice sheet is triggered by a rise in sea level and takes around 6000 years to complete. The ice sheet then halts close to the present state and no collapse takes place. This Holocene deglaciation appears to have added 6–8 million km3 of ice to the world oceans, corresponding with an Antarctic contribution to world-wide sea level of 12–15 m.

scholarly journals The Antarctic Ice Sheet During the Last Glacial-Interglacial Cycle: A Three-Dimensional Experiment

1990 ◽  
Vol 14 ◽  
pp. 115-119 ◽  
Author(s):  
Philippe Huybrechts
Keyword(s):  
Sea Level ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Weddell Sea ◽  
The West ◽  
Antarctic Ice Sheet ◽  
West Antarctic Ice Sheet ◽  
Last Glacial ◽  
West Antarctic ◽  
The Last Glacial

A complete three-dimensional thermo-mechanical ice-shect model for the entire Antarctic ice sheet, including an ice shelf, grounding line-dynamics and isostatic bed adjustment, is employed to simulate the response of the ice sheet during the last glacial-interglacial cycle with respect to changing environmental conditions. To do this, the Vostok temperature signal is used to force changes in surface temperature and accumulation rate and sea level prescribed by a piecewise linear sawtooth function. Model calculations started at 160 ka B.P. In line with glacial geological evidence, the most pronounced fluctuations are found in the West Antarctic ice sheet and appear to be essentially controlled by changes in eustatic sea level. Grounding occurs more readily in the Weddell Sea than in the Ross Sea and, due to the long time scales involved, the ice sheet does not reach its full glacial extent until 16 ka B.p. The concomitant disintegration of the West Antarctic ice sheet is triggered by a rise in sea level and takes around 6000 years to complete. The ice sheet then halts close to the present state and no collapse takes place. This Holocene deglaciation appears to have added 6–8 million km3 of ice to the world oceans, corresponding with an Antarctic contribution to world-wide sea level of 12–15 m.

Asynchronous instability of NE ice streams of the Laurentide Ice Sheet recorded in the marine sediments of Labrador Sea during the last glacial cycle

2020 ◽  
Author(s):  
Harunur Rashid ◽  
Mary Smith ◽  
Min Zeng ◽  
Yang Wang ◽  
Julie Drapeau ◽  
...  
Keyword(s):  
Ice Sheet ◽  
Laurentide Ice Sheet ◽  
Labrador Sea ◽  
Glacial Cycle ◽  
Ice Streams ◽  
Last Glacial ◽  
Ice Stream ◽  
Cumberland Sound ◽  
Detrital Carbonate ◽  
The Last Glacial

<p>Hughes et al. (1977) hypothesized of a pan-Arctic Ice Sheet that behaved as a single dynamic system during the Last Glacial Maximum. Moreover, the authors suggested a nearly grounded ice shelf in Davis Strait implying that little or no exchange between Baffin Island and the Labrador Sea. Here we present data at 1-cm (<100 years) resolution between ~12 ka and 45 ka that shed light on the discharge from Hudson Strait and Lancaster Sound ice streams of the Late Pleistocene Laurentide Ice Sheet. A reference sediment core at 938 m water depth on the SE Baffin Slope was investigated with new oxygen isotope stratigraphy, X-ray fluorescence geochemistry, and 18 14C-AMS dates and correlated to 14 regional deep-water cores. Detrital carbonate-rich sediment layers H0-H4 were derived principally from Hudson Strait. Shortly after H2 and H3, the shelf-crossing Cumberland Sound ice stream supplied dark brown ice-proximal stratified sediments but no glacigenic debris-flow deposits. The counterparts of H3, H4, and (?)H5 events in the deep Labrador basin are 4–10 m thick units of thin-bedded carbonate-rich mud turbidites from glacigenic debris flows on the Hudson Strait slope. The behavior of the Hudson Strait ice stream changed through the last glacial cycle. The Hudson Strait ice stream remained at the shelf break in H3-H5 but retreated rapidly across the shelf in H0-H2 and did not deglaciate Hudson Bay. During this time, Cumberland Sound ice twice reached the shelf edge. In H3–H5, it remained at the shelf break long enough to supply thick turbidites. Minor supply of carbonate-rich sediment from Baffin Bay allows chronologic integration of the Baffin Bay and Labrador Sea detrital carbonate records, which is diachronous with respect to Heinrich events. The asynchrony of the carbonate events implies an open seaway through Davis Strait. Our data suggest that the maximum extent of ice streams in Hudson Strait, Cumberland Sound, and Lancaster Sound was neither synchronous.</p>

scholarly journals Siple Coast Ice Streams in a General Antarctic Ice Sheet Model

2005 ◽  
Vol 18 (13) ◽  
pp. 2194-2198 ◽  
Author(s):  
Mikhail Verbitsky
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Sensitivity Study ◽  
Temperature Pattern ◽  
Ice Streams ◽  
Antarctic Ice Sheet ◽  
West Antarctic ◽  
Pressure Melting ◽  
Basal Melting ◽  
The Antarctic

Abstract In an earlier paper by Verbitsky and Saltzman, a vertically integrated, high-resolution, nonlinearly viscous, nonisothermal ice sheet model was presented to calculate the “present-day” equilibrium regime of the Antarctic ice sheet. Steady-state solutions for the ice topography and thermodynamics, represented by the extent of the areas of basal melting, were shown to be in good agreement with both observations and results obtained from other three-dimensional thermodynamical equations. The solution for the basal temperature field of the West Antarctic Siple Coast produced areas at the pressure melting point separated by strips of frozen-to-bed ice, the structure of which looks very similar to ice streams A–E. Since the possible response of the Siple Coast basal temperature pattern to global warming and to associated changes in the snowfall rate is not obvious, a special sensitivity study was conducted. Results of such a study suggest that increased precipitation rate and associated intensification of ice advection can effectively “shut down” West Antarctic ice streams.

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