Introduction

1998 ◽  
Vol 10 (3) ◽  
pp. 225-226
Author(s):  
Ian D. Goodwin ◽  
Carol J. Pudsey
Keyword(s):  
Regional Differences ◽  
Late Quaternary ◽  
Ice Sheet ◽  
List Type ◽  
Glacial Cycle ◽  
The Holocene ◽  
Last Glacial ◽  
Glacial Stage ◽  
The Antarctic ◽  
The Last Glacial

This issue contains a group of papers selected from those presented at the 1st workshop of the SCAR-GLOCHANT and IGBP-PAGES cosponsored programme on the Late Quaternary Sedimentary Record of the Antarctic Ice Margin Evolution (ANTIME), held in Hobart, 6-1 1 July 1997. ANTIME is focused on the circurn Antarctic reconstruction of palaeoclimate, palaeoenvironment, and ice sheet palaeogeography throughout the last glacial cycle. There were 65 participants from Australia, USA, UK, Italy, Spain, Japan, Sweden, Germany and Russia at the workshop. The participants included representatives of PAGES, IMAGES, and INQUA. The workshop included three scientific sessions on: Extent, timing and regional differences during Glacial Stage 2 (10–30 kyr BP) in Antarctica, from the terrestrial and marine records;Climatic, environmental and glacial events during the Holocene;Late Quaternary geochronological problems in Antarctica.

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 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.

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 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 Investigating the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle

2009 ◽  
Vol 5 (3) ◽  
pp. 329-345 ◽  
Author(s):  
S. Bonelli ◽  
S. Charbit ◽  
M. Kageyama ◽  
M.-N. Woillez ◽  
G. Ramstein ◽  
...  
Keyword(s):  
Northern Hemisphere ◽  
Climate Model ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Glacial Cycle ◽  
Last Glacial ◽  
Atmospheric Co2 Concentration ◽  
The Last Glacial

Abstract. A 2.5-dimensional climate model of intermediate complexity, CLIMBER-2, fully coupled with the GREMLINS 3-D thermo-mechanical ice sheet model is used to simulate the evolution of major Northern Hemisphere ice sheets during the last glacial-interglacial cycle and to investigate the ice sheets responses to both insolation and atmospheric CO2 concentration. This model reproduces the main phases of advance and retreat of Northern Hemisphere ice sheets during the last glacial cycle, although the amplitude of these variations is less pronounced than those based on sea level reconstructions. At the last glacial maximum, the simulated ice volume is 52.5×1015 m3 and the spatial distribution of both the American and Eurasian ice complexes is in reasonable agreement with observations, with the exception of the marine parts of these former ice sheets. A set of sensitivity studies has also been performed to assess the sensitivity of the Northern Hemisphere ice sheets to both insolation and atmospheric CO2. Our results suggest that the decrease of summer insolation is the main factor responsible for the early build up of the North American ice sheet around 120 kyr BP, in agreement with benthic foraminifera δ18O signals. In contrast, low insolation and low atmospheric CO2 concentration are both necessary to trigger a long-lasting glaciation over Eurasia.

scholarly journals Influence of ablation-related processes in the built-up of simulated Northern Hemisphere ice sheets during the last glacial cycle

2012 ◽  
Vol 6 (6) ◽  
pp. 4897-4938 ◽  
Author(s):  
S. Charbit ◽  
C. Dumas ◽  
M. Kageyama ◽  
D. M. Roche ◽  
C. Ritz
Keyword(s):  
Northern Hemisphere ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Glacial Cycle ◽  
Satisfactory Description ◽  
Last Glacial ◽  
Transient Simulations ◽  
Main Driver ◽  
The Impact ◽  
The Last Glacial

Abstract. Since the original formulation of the positive-degree-day (PDD) method, different PDD calibrations have been proposed in the literature in response to the increasing number of observations. Although these formulations provide a satisfactory description of the present-day Greenland geometry, they have not all been tested for paleo ice sheets. Using the climate-ice sheet model CLIMBER-GRISLI coupled with different PDD models, we evaluate how the parameterization of the ablation may affect the evolution of Northern Hemisphere ice sheets in the transient simulations of the last glacial cycle. Results from fully coupled simulations are compared to time-slice experiments carried out at different key periods of the last glacial period. We find large differences in the simulated ice sheets according to the chosen PDD model. These differences occur as soon as the onset of glaciation, therefore affecting the subsequent evolution of the ice system. To further investigate how the PDD method controls this evolution, special attention is given to the role of each PDD parameter. We show that glacial inception is critically dependent on the representation of the impact of the temperature variability from the daily to the inter-annual time scale, whose effect is modulated by the refreezing scheme. Finally, an additional set of sensitivity experiments has been carried out to assess the relative importance of melt processes with respect to initial ice sheet configuration in the construction and the evolution of past Northern Hemisphere ice sheets. Our analysis reveals that the impacts of the initial ice sheet condition may range from quite negligible to explaining about half of the LGM ice volume depending on the representation of stochastic temperature variations which remain the main driver of the evolution of the ice system.

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