Spatial variability of the major chemistry of the Antarctic ice sheet

A compilation of reliable data for sodium, nitrate, chloride and sulphate has been made. NO3 concentrations arc remarkably consistent across Antarctica, though there appears to be some correlation with altitude and accumulation rate. Post-depositional loss of NO3- is important at low-accumulation sites. Cl concentration (either measured directly or calculated from Na+ via the sea salt ratio) decreases with distance from the coast, though the decline is less rapid if the coastal topography is not steep or mountainous. Excess sulphate (xsSO42) concentration (here calculated from normal sea-salt ratios with Na+ or Cl) also declines with distance from the coast, though less quickly than Cl-. Fractionation of sea-salt ions makes the calculation of SO42- uncertain.

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The Weddell Sea region: an important precipitation channel to the interior of the Antarctic ice sheet as revealed by glaciochemical investigation of surface snow along the longest trans-Antarctic route

Annals of Glaciology ◽

10.3189/172756499781821012 ◽

1999 ◽

Vol 29 ◽

pp. 55-60 ◽

Cited By ~ 5

Author(s):

Qin Dahe ◽

Paul A. Mayewski ◽

Ren Jiawen ◽

Xiao Cunde ◽

Sun Junying

Keyword(s):

Ice Sheet ◽

Weddell Sea ◽

Sea Salt ◽

East Antarctica ◽

Antarctic Ice Sheet ◽

Air Masses ◽

Antarctic Plateau ◽

Salt Ions ◽

Surface Snow ◽

The Antarctic

AbstractGlaciochemical analysis of surface snow samples, collected along a profile crossing the Antarctic ice sheet from the Larsen Ice Shelf, Antarctic Peninsula, via the Antarctic Plateau through South Pole, Vostok and Komsomolskaya to Mirny station (at the east margin of East Antarctica), shows that the Weddell Sea region is an important channel for air masses to the high plateau of the Antarctic ice sheet (>2000 m a.s.l.). This opinion is supported by the following. (1) The fluxes of sea-salt ions such as Na+, Mg2 + and CF display a decreasing trend from the west to the east of interior Antarctica. In |eneral, as sea-salt aerosols are injected into the atmosphere over the Antarctic ice sheet from the Weddell Sea, large aerosols tend to decrease. For the inland plateau, few large particles of sea-salt aerosol reach the area, and the sea-salt concentration levels are low (2) The high altitude of the East Antarctic plateau, as well as the polar cold high-pressure system, obstruct the intrusive air masses mainly from the South Indian Ocean sector. (3) For the coastal regions of the East Antarctic ice sheet, the elevation rises to 2000 m over a distance from several to several tens of km. High concentrations of sea salt exist in snow in East Antarctica but are limited to a narrow coastal zone. (4) Fluxes of calcium and non-sea-salt sulfate in snow from the interior plateau do not display an eastward-decreasing trend. Since calcium is mainly derived from crustal sources, and nssSO42- is a secondary aerosol, this again confirms that the eastward-declining tendency of sea-salt ions indicates the transfer direction of precipitation vapor.

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The Dynamics of the Antarctic Ice Sheet

Annals of Glaciology ◽

10.3189/s026030550000690x ◽

1989 ◽

Vol 12 ◽

pp. 16-22 ◽

Cited By ~ 5

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.

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Large-Scale Numerical Modelling of the Antarctic Ice Sheet

Annals of Glaciology ◽

10.1017/s0260305500002500 ◽

1982 ◽

Vol 3 ◽

pp. 42-49 ◽

Cited By ~ 54

Author(s):

W.F. Budd ◽

I.N. Smith

Keyword(s):

Sea Level ◽

Large Scale ◽

Accumulation Rate ◽

Ice Sheet ◽

Ice Thickness ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Flow Parameters ◽

The Antarctic ◽

Thinning Rate

A large-scale dynamic numerical model of the Antarctic ice sheet has been developed to study its present state of ice flow and mass balance as well as its response to long-term changes of climate or sea-level.The flow of ice over a two-dimensional grid is determined from the ice thickness, the basal shear stress, the bedrock depth, and ice flow parameters derived from velocities of existing ice sheets. The change in ice thickness with time is governed by the continuity equation involving the ice flux divergence and the ice accumulation or ablation. At the ice sheet seaward boundary, a floating criterion and floating ice thinning rate apply. Bedrock depression with a time-delayed response dependent on the history of the ice load is also included.A 61 × 61 point grid with 100 km spacing has been used to represent the ice-sheet surface, bedrock, and accumulation rate. The model has been used to simul a te the growth of the present ice sheet and i ts reaction to changes of sea-level, bedrock depression, accumulation rate, ice flow parameters, and the iceshelf thinning rate.Preliminary results suggest that the present ice sheet is not in equilibrium but rather is still adjusting to changes of these parameters.

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The Dynamics of the Antarctic Ice Sheet

Annals of Glaciology ◽

10.1017/s026030550000690x ◽

1989 ◽

Vol 12 ◽

pp. 16-22 ◽

Cited By ~ 24

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.

Download Full-text

Large-Scale Numerical Modelling of the Antarctic Ice Sheet

Annals of Glaciology ◽

10.3189/s0260305500002500 ◽

1982 ◽

Vol 3 ◽

pp. 42-49 ◽

Cited By ~ 4

Author(s):

W.F. Budd ◽

I.N. Smith

Keyword(s):

Sea Level ◽

Large Scale ◽

Accumulation Rate ◽

Ice Sheet ◽

Ice Thickness ◽

Ice Flow ◽

Antarctic Ice Sheet ◽

Flow Parameters ◽

The Antarctic ◽

Thinning Rate

A large-scale dynamic numerical model of the Antarctic ice sheet has been developed to study its present state of ice flow and mass balance as well as its response to long-term changes of climate or sea-level.The flow of ice over a two-dimensional grid is determined from the ice thickness, the basal shear stress, the bedrock depth, and ice flow parameters derived from velocities of existing ice sheets. The change in ice thickness with time is governed by the continuity equation involving the ice flux divergence and the ice accumulation or ablation. At the ice sheet seaward boundary, a floating criterion and floating ice thinning rate apply. Bedrock depression with a time-delayed response dependent on the history of the ice load is also included.A 61 × 61 point grid with 100 km spacing has been used to represent the ice-sheet surface, bedrock, and accumulation rate. The model has been used to simul a te the growth of the present ice sheet and i ts reaction to changes of sea-level, bedrock depression, accumulation rate, ice flow parameters, and the iceshelf thinning rate.Preliminary results suggest that the present ice sheet is not in equilibrium but rather is still adjusting to changes of these parameters.

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Balance velocities and measured properties of the Antarctic ice sheet from a new compilation of gridded data for modelling

Annals of Glaciology ◽

10.3189/172756400781820778 ◽

2000 ◽

Vol 30 ◽

pp. 52-60 ◽

Cited By ~ 53

Author(s):

Philippe Huybrechts ◽

Daniel Steinhage ◽

Frank Wilhelms ◽

Jonathan Bamber

Keyword(s):

Accumulation Rate ◽

Ice Sheet ◽

Data Sources ◽

Altimeter Data ◽

Ice Thickness ◽

Radar Altimeter ◽

Antarctic Ice Sheet ◽

Ice Shelves ◽

Dronning Maud Land ◽

The Antarctic

AbstractThis paper presents a new compilation of gridded datasets for three-dimensional modelling of the Antarctic ice sheet. These are for surface elevation, ice thickness, bedrock elevation and accumulation rate as interpolated on a 281 × 281 mesh with 20 km spacing, and encompass all the ice sheet and surrounding continental shelf. Data sources include the Bamber digital-elevation model from ERS-1 radar-altimeter data, a redigitization of available ice-thickness data, the Giovinetto accumulation data, recent ice-thickness data from British and German expeditions as well as accumulation data from German and Norwegian expeditions. In particular, new data were incorporated for the Filchner-Ronne Ice Shelf and for Dronning Maud Land, Antarctica, arising from the EPICA pre-site survey. Special attention was devoted to matching the various data sources carefully, both among themselves and across the grounding line and below the ice shelves, to enable ice-sheet expansion and retreat in dynamic situations. As an application, the balance flow is calculated over the entire ice sheet using a two-dimensional finite-difference scheme and compared with a previous assessment. This brought to light the existence of ice-streaming features extending well inland. A detailed zoom over Dronning Maud Land exhibits the general flow characteristics of interest for locating a future deep-drilling site. As a by-product, an updated value of 26.4 × 106km3 was obtained for the total volume of the ice sheet and ice shelves, or equivalent to 61.1 m of global sea-level rise after removal of the ice sheet and subsequent oceanic invasion and isostatic rebound. The total accumulation over the grounded ice sheet, including the Antarctic Peninsula, is 1924 Gta−1, or between 5 and 20% higher than earlier estimates. Including all the ice shelves, the value is 2344 Gt a−1.

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