Freezing of the Active Layer on the Coastal Plain of the Alaskan Arctic

Abstract

Upward freezing from the bottom of the active layer started at the end of August or beginning of September when the ground surface temperature was above 0°C. About one‐third of the active layer froze upwards at the West Dock, Deadhorse and Franklin Bluffs sites. Temperatures were warmer than −1°C at the maximum depth of the active layer 20 days after the freeze‐up date with the temperature maximum near the base of the active layer. This behaviour was caused by unfrozen water in the active layer and near‐surface permafrost. A numerical model was used to determine the most appropriate unfrozen water content curves at each site. Modelling also indicates that a layer with increased unfrozen water content existed during cooling of the active layer following freeze‐up and during warming prior to thawing. At the Deadhorse site, this layer continued from the ground surface to a depth of 0.3 m in 1987 and 0.36 m in 1991. For Franklin Bluffs in 1987, for West Dock in 1988, and for Barrow in 1993 the thickness of this layer was 0.1 m and it was located between 0.2 and 0.3 m at Franklin Bluffs, between 0.15 and 0.25 m at West Dock, and between 0.21 and 0.31 m at Barrow. The unfrozen water contents for these layers were relatively large at low temperatures. Analytical calculations of the apparent thermal diffusivity showed that its observed variations with temperature were due to the latent heat effects of the unfrozen water. Microbial activity and trace gas evolution during the winter may be influenced by the presence of the unfrozen water. © 1997 John Wiley & Sons, Ltd.

Evaluation of the algorithms and parameterizations for ground thawing and freezing simulation in permafrost regions

“…The importance of unfrozen water content on frozen soil thermal properties and GTFD simulation has been widely demonstrated [e.g., Anderson and Tice , 1972; Nakano and Brown , 1972; Andersland and Ladanyi , 1994, pp. 40–43; Osterkamp and Romanovsky , 1997; Romanovsky and Osterkamp , 2000]. As soil temperature is not explicitly simulated in analytical algorithms, only a constant unfrozen water content is assigned to each type of frozen soil [e.g., Woo et al , 2004; Carey and Woo , 2005; Yi et al , 2006], unless observations are available [e.g., Hayashi et al , 2007].…”

Response of soil heat-water processes to vegetation cover on the typical permafrost and seasonally frozen soil in the headwaters of the Yangtze and Yellow Rivers

“…The analysis of soil water and heat processes was divided into four stages based on freezethaw state of the active layers: the freezing process stage (from mid-October to late December), when soil profile is in the process of freezing; the frozen stage (from early January to late April), when the soil profile is completely frozen; the thawing process stage (from early May to early July), when soil profile is in the process of thawing; and the non-frozen stage (from mid-July to the beginning of the next freezing process stage), when the soil profile is completely melted [27] . 2.1.1 Response of soil temperature to vegetation covers in active layers of a permafrost soil.…”

“…Similar to the Fenghuoshan permafrost region's soils, the freeze-thaw period was divided into four stages: freezing process (mid-November to late December); frozen (early January to late March); thawing process (early April to early May); non-frozen (mid-May to next year's freezing process stage) [27] . 2.2.1 Response of soil temperature to vegetation covers in seasonally frozen soil.…”

Impacts of wildfire on the permafrost in the boreal forests of Interior Alaska

“…Drilling records were used to determine the lithology and the initial approximate thermal properties of the soils in the thawed and frozen states. The thermal properties (including unfrozen water content curves) were refined using a trial and error method [ Osterkamp and Romanovsky , 1997]. The results of modeling for the undisturbed site were discussed by Osterkamp and Romanovsky [1999].…”