Multi-channel ground-penetrating radar to explore spatial variations in thaw depth and moisture content in the active layer of a permafrost site

摘要

Multi-channel ground-penetrating radar (GPR) was applied at a permafrost site onthe Tibetan Plateau to investigate the influence of surface properties and soiltexture on the late-summer thaw depth and average soil moisture content ofthe active layer. Measurements were conducted on an approximately 85 × 60 m2sized area with surface and soil textural properties that rangedfrom medium to coarse textured bare soil to finer textured, sparsely vegetatedareas covered with fine, wind blown sand, and it included the bed of a gravelroad. The survey allowed a clear differentiation of the various units. It showed(i) a shallow thaw depth and low average soil moisture content below thesand-covered, vegetated area, (ii) an intermediate thaw depth and high averagesoil moisture content along the gravel road, and (iii) an intermediate to deepthaw depth and low to intermediate average soil moisture content in the baresoil terrain. From our measurements, we found hypotheses for the permafrostprocesses at this site leading to the observed late-summer thaw depth and soilmoisture conditions. The study clearly indicates the complicated interactionsbetween surface and subsurface state variables and processes in thisenvironment. Multi-channel GPR is an operational technology to efficientlystudysuch a system at scales varying from a few meters to a few kilometers.