Regensburg 2013 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 16: Pattern Formation

DY 16.2: Vortrag

Mittwoch, 13. März 2013, 10:00–10:15, H46

Patterned ground in permafrost: an experimental study — •Antoine Fourrière and Lucas Goehring — Max-Planck-Institut für Dynamik und Selbstorganisation, Göttingen, Deutschland

Permafrost experiences annual freezing and thawing cycles. Differential frost heave results in the slow and natural emergence of periodic patterns at the surface of these soils. Due to the very long timescales involved, i.e. 1 to several thousand of years, field measurements can hardly provide the data needed to distinguish between the different theoretical ideas that could explain this pattern formation process. In particular, the physical mechanisms that link small-scale dynamics, such as cryosuction of water through a porous medium or the expansion of a frozen fringe, to meter-scale patterned ground are still an issue and have to be adressed. Here we present experimental work that mimics the initial stages of patterned ground formation in permafrost. We observe the evolution of surface topography for a granulate volume of 20 × 20 × 10 cm during several freeze-thaw cycles. The particle size distribution and the water fraction are varied. Surface modulation is observed for particular composition of the soil. The temperature evolution T(z,t) inside the sample is modelled in the framework of the Stefan problem. By comparing the model results with the measured temperature profile, simple ideas like the evolution of the freezing front and the presence of a frozen fringe can be tested.