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Temperature variation and apparent thermal diffusivity in the refreezing active layer, Toolik Lake, Alaska
Author(s) -
Hinkel K. M.,
Outcalt S. I.,
Nelson F. E.
Publication year - 1990
Publication title -
permafrost and periglacial processes
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.867
H-Index - 76
eISSN - 1099-1530
pISSN - 1045-6740
DOI - 10.1002/ppp.3430010306
Subject(s) - thermal diffusivity , permafrost , advection , active layer , thermal , geology , electrical conductor , diffusion , atmospheric sciences , layer (electronics) , materials science , thermodynamics , oceanography , composite material , physics , thin film transistor
Temperatures were sampled at eight‐hour intervals over a five‐month period within the refreezing active layer at Toolik Lake, Alaska. The variance spectra of the temperature series, calculated as a function of wavelength, reveal relatively high‐frequency (sub‐diurnal) temperature fluctuations near the base of the active layer during refreezing, behaviour that is not consistent with a purely conductive system. The thermal records were also used in a numerical scheme to calculate apparent thermal diffusivity at regularly spaced depths in the substrate. Widely fluctuating positive and negative diffusivity values suggest that non‐conductive processes play an important role in heat transport during and after freezeback. Phase transformations, vapour diffusion and water advection all can enhance or oppose the conductive tendency. Models based exclusively on conductive principles are inadequate to explain thermal evolution in the dynamic near‐surface layer of permafrost regions.