scholarly journals The Dynamics of the Antarctic Ice Sheet

1989 ◽  
Vol 12 ◽  
pp. 16-22 ◽  
Author(s):  
W.F. Budd ◽  
D. Jenssen
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Accumulation Rate ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Surface Velocity ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Past ◽  
The Antarctic

A three-dimensional dynamic, thermodynamic ice-sheet model has been developed to simulate the past, present, and future behaviour of the Antarctic ice sheet. The present ice velocities depend on the deep ice temperatures which in turn depend on the past changes of the ice sheet, including surface temperature, accumulation rate, and ice thickness. The basal temperatures are also strongly dependent on the geothermal heat flux. The model has therefore been used to study the effect on the basal temperatures, of changes to the geothermal heat flux, as well as the past changes of surface temperature and accumulation rate based on results obtained from the Vostok deep ice core. The model is also used to compute the distribution of surface velocity required to balance the present accumulation rate and the dynamics velocity based on the stress, temperature, and flow properties of ice, for the internal deformation, plus a component due to ice sliding. These velocities are compared to observed surface velocities in East Antarctica to assess the state of balance and the performance of the dynamics formulation.

scholarly journals The Dynamics of the Antarctic Ice Sheet

1989 ◽  
Vol 12 ◽  
pp. 16-22 ◽  
Author(s):  
W.F. Budd ◽  
D. Jenssen
Keyword(s):  
Heat Flux ◽  
Surface Temperature ◽  
Accumulation Rate ◽  
Three Dimensional ◽  
Ice Sheet ◽  
Surface Velocity ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Past ◽  
The Antarctic

A three-dimensional dynamic, thermodynamic ice-sheet model has been developed to simulate the past, present, and future behaviour of the Antarctic ice sheet. The present ice velocities depend on the deep ice temperatures which in turn depend on the past changes of the ice sheet, including surface temperature, accumulation rate, and ice thickness. The basal temperatures are also strongly dependent on the geothermal heat flux. The model has therefore been used to study the effect on the basal temperatures, of changes to the geothermal heat flux, as well as the past changes of surface temperature and accumulation rate based on results obtained from the Vostok deep ice core. The model is also used to compute the distribution of surface velocity required to balance the present accumulation rate and the dynamics velocity based on the stress, temperature, and flow properties of ice, for the internal deformation, plus a component due to ice sliding. These velocities are compared to observed surface velocities in East Antarctica to assess the state of balance and the performance of the dynamics formulation.

scholarly journals Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

1996 ◽  
Vol 23 ◽  
pp. 382-387 ◽  
Author(s):  
I. Hansen ◽  
R. Greve
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Ice Sheet ◽  
Physical Parameters ◽  
Water Mixture ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Real ◽  
Thermomechanical Behaviour ◽  
The Antarctic

An approach to simulate the present Antarctic ice sheet with reaped to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important because an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice water mixture. Measurements indicate that the geothermal heat flux below the Antarctic ice sheet appears to be remarkably higher than the standard value of 42 m W m−2 that is usually applied for Precambrian shields in ice-sheet modelling. Since the extent of temperate ice at the base is highly dependent on this heat input from the lithosphere, an adequate choice is crucial for realistic simulations. We shall present a series of steady-state results with varied geothermal heat flux and demonstrate that the real ice-sheet topography can be reproduced fairly well with a value in the range 50–60 m W m−2. Thus, the physical parameters of ice (especially the enhancement factor in Glen’s flow law) as used by Greve (1995) for polythermal Greenland ice-sheet simulations can be adopted without any change. The remaining disagreements may he explained by the neglected influence of the ice shelves, the rather coarse horizontal resolution (100 km), the steady-state assumption and possible shortcomings in the parameterization of the surface mass balance.

scholarly journals Polythermal modelling of steady states of the Antarctic ice sheet in comparison with the real world

1996 ◽  
Vol 23 ◽  
pp. 382-387 ◽  
Author(s):  
I. Hansen ◽  
R. Greve
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Ice Sheet ◽  
Physical Parameters ◽  
Water Mixture ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Real ◽  
Thermomechanical Behaviour ◽  
The Antarctic

An approach to simulate the present Antarctic ice sheet with reaped to its thermomechanical behaviour and the resulting features is made with the three-dimensional polythermal ice-sheet model designed by Greve and Hutter. It treats zones of cold and temperate ice as different materials with their own properties and dynamics. This is important because an underlying layer of temperate ice can influence the ice sheet as a whole, e.g. the cold ice may slide upon the less viscous binary ice water mixture.Measurements indicate that the geothermal heat flux below the Antarctic ice sheet appears to be remarkably higher than the standard value of 42 m W m−2 that is usually applied for Precambrian shields in ice-sheet modelling. Since the extent of temperate ice at the base is highly dependent on this heat input from the lithosphere, an adequate choice is crucial for realistic simulations. We shall present a series of steady-state results with varied geothermal heat flux and demonstrate that the real ice-sheet topography can be reproduced fairly well with a value in the range 50–60 m W m−2. Thus, the physical parameters of ice (especially the enhancement factor in Glen’s flow law) as used by Greve (1995) for polythermal Greenland ice-sheet simulations can be adopted without any change. The remaining disagreements may he explained by the neglected influence of the ice shelves, the rather coarse horizontal resolution (100 km), the steady-state assumption and possible shortcomings in the parameterization of the surface mass balance.

scholarly journals Geothermal flux beneath the Antarctic Ice Sheet derived from measured temperature profiles in deep boreholes

2020 ◽  
Author(s):  
Pavel Talalay ◽  
Yazhou Li ◽  
Laurent Augustin ◽  
Gary Clow ◽  
Jialin Hong ◽  
...  
Keyword(s):  
Heat Flux ◽  
Heat Flow ◽  
Ice Core ◽  
Ice Sheet ◽  
High Heat ◽  
Temperature Profiles ◽  
Measured Temperature ◽  
Geothermal Heat ◽  
Antarctic Ice Sheet ◽  
The Antarctic

Abstract. The temperature at the Antarctic ice sheet bed and the temperature gradient in subglacial rocks have been directly measured only a few times, although extensive thermodynamic modelling has been used to estimate geothermal heat flux under ice sheet. During the last five decades, deep ice-core drilling projects at six sites – Byrd, WAIS Divide, Dome C, Kohnen, Dome F, and Vostok – have succeeded in reaching to, or nearly to, the bed in inland locations in Antarctica. When temperature profiles in these boreholes and heat flow model are combined with estimations of vertical velocity, the heat flow at ice sheet base is translated to a geothermal heat flux of 117.8 ± 3.3 mW m−2 at Byrd, 67.3 ± 8.6 mW m−2 at Dome C, 79.0 ± 5.0 mW m−2 at Dome F, and −3.3 ± 5.6 mW m−2 at Vostok, close to predicted values. However, estimations at Kohnen and WAIS Divide gave flux of 161.5 ± 10.2 mW m−2 and 251.3 ± 24.1 mW m−2, respectively, far higher than that predicted by existing heat flow models. The question arises as to whether this high heat flow represents regional values, or if the Kohnen and WAIS Divide boreholes were drilled over local hot spots.

scholarly journals Are longitudinal ice-surface structures on the Antarctic Ice Sheet indicators of long-term ice-flow configuration?

2014 ◽  
Vol 2 (2) ◽  
pp. 911-933 ◽  
Author(s):  
N. F. Glasser ◽  
S. J. A. Jennings ◽  
M. J. Hambrey ◽  
B. Hubbard
Keyword(s):  
Flow Line ◽  
Ice Sheet ◽  
Surface Structures ◽  
Surface Velocity ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Ice Surface ◽  
Ice Stream ◽  
The Antarctic

Abstract. Continent-wide mapping of longitudinal ice-surface structures on the Antarctic Ice Sheet reveals that they originate in the interior of the ice sheet and are arranged in arborescent networks fed by multiple tributaries. Longitudinal ice-surface structures can be traced continuously down-ice for distances of up to 1200 km. They are co-located with fast-flowing glaciers and ice streams that are dominated by basal sliding rates above tens of m yr-1 and are strongly guided by subglacial topography. Longitudinal ice-surface structures dominate regions of converging flow, where ice flow is subject to non-coaxial strain and simple shear. Associating these structures with the AIS' surface velocity field reveals (i) ice residence times of ~ 2500 to 18 500 years, and (ii) undeformed flow-line sets for all major flow units analysed except the Kamb Ice Stream and the Institute and Möller Ice Stream areas. Although it is unclear how long it takes for these features to form and decay, we infer that the major ice-flow and ice-velocity configuration of the ice sheet may have remained largely unchanged for several thousand years, and possibly even since the end of the last glacial cycle. This conclusion has implications for our understanding of the long-term landscape evolution of Antarctica, including large-scale patterns of glacial erosion and deposition.

scholarly journals Climate, the Antarctic ice sheet and ground heat flux

1995 ◽  
Vol 21 ◽  
pp. 144-148
Author(s):  
Garth W. Paltridge ◽  
Christopher M. Zweck
Keyword(s):  
Heat Flux ◽  
Steady State ◽  
Climate Models ◽  
Global Climate ◽  
Ice Sheet ◽  
Global Climate Models ◽  
Balance Model ◽  
Antarctic Ice Sheet ◽  
Ground Heat Flux ◽  
The Antarctic

A simple steady-state energy and mass-balance model of the Antarctic ice sheet is developed. Basically it is a set of two equations with two unknowns of steady-state height h and potential basal temperature Tb. Tb determines whether, and to what extent, there is liquid water at the base of the ice which in turn affects the values of h and Tb. Simultaneous changes of sea-level temperature and precipitation (changes related to each other as might be expected from global climate models) indicate a maximum in the field of possible steady-state ice volumes which may not be far from the presently observed conditions. The possibility of cyclical variation in ground heat flux associated with convection of water and heat in the continental crust is discussed. The mechanism might be capable of generating cycles of ice-sheet volume with relatively short periods similar to those of Milankovitch forcing.

scholarly journals The Heat Regime of the Central Parts of the Antarctic Ice Sheet with Changing Climate (Abstract only)

1982 ◽  
Vol 3 ◽  
pp. 343
Author(s):  
V.R. Barbash ◽  
I.A. Zotikov
Keyword(s):  
Numerical Modelling ◽  
Surface Temperature ◽  
Greenhouse Effect ◽  
Ice Sheet ◽  
Heat Regime ◽  
Antarctic Ice Sheet ◽  
Temperature Changes ◽  
Dissipation Term ◽  
Vostok Station ◽  
The Antarctic

The heat regime and dynamics of the Antarctic ice sheet are studied using numerical modelling for two flow lines, one of which passes Vostok station and the other Byrd station. A two-dimensional non-steady heat-transfer equation with an energy dissipation term was used. The study consists of two parts. The first is a study of velocity and temperature distributions within the glacier under steady-state conditions. The second study was performed assuming surface temperature changes intended to model palaeoclimatic changes for the last 100 ka and also to model future climate changes due to a possible "greenhouse" effect. Computer numerical modelling shows that the Antarctic ice sheet retains a record of the climatic temperature minimum 18 ka BP. Numerical modelling of the greenhouse effect assumes a temperature increasing by 10 deg within the next 100 a; its influence increases after this even if the surface temperature then remains the same for the next 20 ka. It is shown that for the next 1 ka the temperature wave will penetrate only a thin surface layer of the ice. Even in 20 ka the bottom temperature of the ice sheet will still be unchanged. Small increases of ice velocity can produce ice-sheet thinning of the order of 10 mm a−1.

scholarly journals Antarctic Ice-Sheet Topography and Surface-Bedrock Relationships

1986 ◽  
Vol 8 ◽  
pp. 124-128 ◽  
Author(s):  
N.F. McIntyre
Keyword(s):  
Three Dimensional ◽  
Ice Sheet ◽  
Coastal Regions ◽  
Three Dimensional Flow ◽  
Ice Flow ◽  
Antarctic Ice Sheet ◽  
Dimensional Flow ◽  
Ice Velocity ◽  
The Antarctic ◽  
Ice Sheet Topography

Mapping the topography of the Antarctic ice sheet has confirmed that there is, typically, a decrease in the wavelength and increase in the amplitude of surface undulations with distance from ice divides. This pattern is distorted by converging ice flow in coastal regions and by other variations in subglacial relief, ice velocity, and viscosity. The near-symmetry of undulations indicates the extent of three-dimensional flow over bedrock peaks. Spectral analyses indicate the greater response of the ice sheet to bedrock features with longer wavelengths. This is affected, and in some cases dominated, by the inhomogeneous and non-isothermal nature of the ice sheet.

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.

Sign in / Sign up

Export Citation Format

Share Document