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| Titel |
Gelifluction of soil on the Antarctic Peninsula |
| VerfasserIn |
P. D. Hallett, B. Sun, P. G. Dennis, D. H. Hopkins |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250020273
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| Zusammenfassung |
| Gelifluction is a large drop in the mechanical stability of soil that occurs at the onset of
freezing and thawing. On slopes it causes a downward migration of soil, producing
characteristic large lobes in the landscape of many polar terrestrial environments. At the
microscale, the loss in stability and fluxes in soil water potential associated with
gelifluction may influence microbial habitats as ancillary impacts of swelling on
freezing rearranges the solid matrix of soil. With climate change predictions for the
Antarctic Peninsula, cycles of freezing and thawing will likely increase, resulting in
greater impacts from gelifluction. Little research has quantified the process in these
soils, however, with traditional geotechnical characterisation hindered as the large
volumes of soil required are at odds with conservation concerns for the area. In this
study, we quantified gelifluction under highly controlled conditions using small
samples in a parallel plate rheometer. Soils were collected from Signy, Greenwich,
Wiencke, and Livingston Islands, as well as from the northern tip of the Antarctic
Peninsula. An oscillating 10 Pa shear stress was applied to sieved samples equilibrated
to -0.5 kPa water potential. Freezing and thawing was controlled with a peltier
temperature controller, with temperature ramps consisting of 5ºC to -10ºC over 2
hours, followed by -10ºC to 5ºC over two hours, and finally at constant 5ºC for 1
hour. Two freeze-thaw cycles were measured followed by a shear stress ramp until
failure.
After two cycles of freezing and thawing, all soils had similar viscosity (54 kPa s) and
yield stress (1.1 kPa). However, due to gelifluction, viscosities dropped to 23% of the 5ºC
value at the onset of the second thaw cycle, with the extreme values ranging from 10% at
Byers Peninsula on Livingston Island to 34% at Wynn Knolls on Signy Island (P |
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