Permafrost Terrain Stability and Thermokarst Monitoring: - Arctic LCC

46. Grosse, G., Schirrmeister, L., and Malthus, T.J., 2006, Application of Landsat‐7
satellite data and a DEM for the quantification of thermokarst‐affected terrain types in
the periglacial Lena–Anabar coastal lowland: Polar Research, v. 25, no. 1, p. 51–67.
This paper describes the use of Landsat-7 satellite data and a digital elevation model for the
quantification and description of an approximately 3,500-km 2 thermokarst-affected region
in northern Siberia. A supervised classification approach was used to determine various
thermokarst landforms that relied primarily on relief forms and the spectral response of
various tundra vegetation types. The final terrain type classification was composed of eight
major classes (seven land classes and one water class). These were divided into 37
subclasses, and the class composition for some of these subclasses was categorized based on
thermokarst depressions, pingos, river valleys, thermo-erosional valleys, and yedoma
uplands. Thirteen surface classes ultimately were determined to provide good overall
classification accuracy (79 percent), and that 78 percent of the study area was affected
somewhat by thermokarst, thermo-erosion, and related slope processes.
47. Harris, C., and Lewkowicz, A.G., 2000, An analysis of the stability of thawing slopes,
Ellesmere Island, Nunavut, Canada: Canadian Geotechnical Journal, v. 37, no. 2,
p. 449–462.
This paper examined the potential for failure of two slopes showing evidence of previous
active layer detachment slides. Theoretically, detachment failures depend on soil and pore
pressures. By measuring soil pore pressure and active layer depths, the authors were able to
calculate the safety factor for the given slopes, and to estimate the pore pressures needed to
facilitate a detachment slide. Although the tested slopes were in relatively safe states,
changes necessary to induce slides were calculated. Depth of saturation and buried sand
layers were recognized as two potentially important factors. Shear strength was identified as
the most sensitive parameter controlling slope stability; shear strength may decrease
annually when active layers are deep, eventually weakening the soils and allowing slides to
occur.
48. Harris, S.A., 2002, Causes and consequences of rapid thermokarst development in
permafrost or glacial terrain: Permafrost and Periglacial Processes, v. 13, no. 3,
p. 237–242.
This paper compares air, soil, and water temperature at one location to show that heat is
adsorbed differently by soils and water. A lag time between water temperature and ground
temperature was observed, and a large disconnect during cooling was noted when winter
temperatures reached -3°C and -19°C in the lake and the ground, respectively. The
subsurface inflows could have affected the comparison. Discussion focuses on the major
differences between soil and water, including heat capacity, thermal diffusivity, and thermal
conductivity. Translucency and convection are two important factors that are unique to
water and heat storage and exchange. The discussion notes how the differences in thermal
properties of water and soils may lead to thermokarst development and shows photographs
representing the formation of an alas valley.
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