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| Titel |
Compression experiments on artificial, alpine and marine ice: implications for ice-shelf/continental interactions |
| VerfasserIn |
Marie Dierckx, Thomas Goossens, Denis Samyn, Jean-louis Tison |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032172
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| Zusammenfassung |
| Antarctic ice shelves are important components of continental ice dynamics, in that they
control grounded ice flow towards the ocean. As such, Antarctic ice shelves are a key
parameter to the stability of the Antarctic ice sheet in the context of global change. Marine
ice, formed by sea water accretion beneath some ice shelves, displays distinct physical (grain
textures, bubble content, ...) and chemical (salinity, isotopic composition, ...) characteristics
as compared to glacier ice and sea ice.
The aim is to refine Glen’s flow relation (generally used for ice behaviour in deformation)
under various parameters (temperature, salinity, debris, grain size ...) to improve deformation
laws used in dynamic ice shelf models, which would then give more accurate and / or realistic
predictions on ice shelf stability.
To better understand the mechanical properties of natural ice, deformation experiments
were performed on ice samples in laboratory, using a pneumatic compression device. To do
so, we developed a custom built compression rig operated by pneumatic drives. It has
been designed for performing uniaxial compression tests at constant load and under
unconfined conditions. The operating pressure ranges from about 0.5 to 10 Bars. This
allows modifying the experimental conditions to match the conditions found at the
grounding zone (in the 1 Bar range). To maintain the ice at low temperature, the
samples are immersed in a Silicone oil bath connected to an external refrigeration
system. During the experiments, the vertical displacement of the piston and the
applied force is measured by sensors which are connected to a digital acquisition
system.
We started our experiments with artificial ice and went on with continental ice samples
from glaciers in the Alps. The first results allowed us to acquire realistic mechanical data for
natural ice. Ice viscosity was calculated for different types of artificial ice, using Glen’s flow
law, and showed the importance of impurities content and ice crystallography (grain
size, ice fabrics-¦) on the deformation behaviour. Glacier ice was also used in our
experiments. Calculations of the flow parameter A give a value of 3.10e-16 s-1 kPa-3 at a
temperature of -10Ë C. These results are in accordance with previous lab deformation
studies.
Compression tests show the effectiveness of the deformation unit for uniaxial strain
experiment. In the future, deformation of marine ice and of the ice mélange (consisting of a
melange of marine ice, broken blocks of continental ice and blown snow further
metamorphosed into firn and then ice) will be studied, to obtain a comprehensive
understanding of the parameters that influence the behaviour of both ice types and
how they affect the overall flow of the ice shelf and potential future sea level rise. |
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