Variation in Soil Properties Important to Tundra Thermokarst North Slope, Alaska.

Soil BD, water content, and texture are important to soil thermo-insulation, stability and strength that each affecting the susceptibility of tundra to thermokarst damage. These properties are important in three components of the soil profile 1) the organic surface layer that insulates the permafrost, 2) the mineral active layer that provides weight bearing strength and 3) the upper permafrost that is often ice-rich and must be maintained in the frozen state.  We examined data available for soils of 64 sites from across the arctic north slope of Alaska. Site soil profile data were averaged within the three profile components for the major landscape units: Coastal Lowlands and Upland/Foothills, and for terrain units within the landscapes.

For the organic surface layer: thickness, bulk density, and water content are variable both on a micro and landscape scale. Bulk density of this layer tends to be higher on the Coastal Lowlands (average 0.38 g cm^-3) than on the Upland Foothills (average 0.21 g cm^-3) contributing to regional differences in heat transfer and the potential for surface compaction. Organic layers of the Upland/Foothills terrain tend to be more insulating but could be more susceptible to compaction than those of the Coastal Lowlands.

The mineral active layers of the Upland Foothills have higher soil BD and soil textures are heavier than those of the Coastal lowlands (average 1.22 g cm^-3 /loamy in the Upland/Foothills and average 1.03 g cm^-3 /sandy loam for the Coastal Lowlands). Differences result from disparate regional factors such as landscape evolution and the higher average soil organic matter contents in the Coastal Lowland soils compared to the Upland Foothills, average 9.0% and 5.5% C respectively.

The upper permafrost (to 1 meter) is generally high in volumetric water and segregated ice content (52-81%).  But the Polygenic and Lake terrain units of the Coastal Lowlands along with the Upland areas tend to be higher in volumetric water/ice (average 72-76%) than the Foothills tussock tundra area (average 52%) to 1 meter depth.