Abstract
Abstract. Multi-channel ground-penetrating radar (GPR) was applied at a permafrost site on the Tibetan Plateau to investigate the influence of surface properties and soil texture on the late-summer thaw depth and average soil moisture content of the active layer. Measurements were conducted on an approximately 85 × 60 m2 sized area with surface and soil textural properties that ranged from medium to coarse textured bare soil to finer textured, sparsely vegetated areas covered with fine, wind blown sand, and it included the bed of a gravel road. The survey allowed a clear differentiation of the various units. It showed (i) a shallow thaw depth and low average soil moisture content below the sand-covered, vegetated area, (ii) an intermediate thaw depth and high average soil moisture content along the gravel road, and (iii) an intermediate to deep thaw depth and low to intermediate average soil moisture content in the bare soil terrain. From our measurements, we found hypotheses for the permafrost processes at this site leading to the observed late-summer thaw depth and soil moisture conditions. The study clearly indicates the complicated interactions between surface and subsurface state variables and processes in this environment. Multi-channel GPR is an operational technology to efficiently study such a system at scales varying from a few meters to a few kilometers.
Highlights
Permafrost on the Tibetan Plateau reacts very sensitively to climate change (Liu and Chen, 2000; Zhao et al, 2010)
Multi-channel ground-penetrating radar (GPR) was applied at a permafrost site on the Tibetan Plateau to investigate the influence of surface properties and soil texture on the late-summer thaw depth and average soil moisture content of the active layer
In contrast to the former study of Gerhards et al (2008) who applied data from a single GPR transect crossing a small creek at this permafrost site to demonstrate the new multichannel GPR technique, this study aims at the spatial exploration of active layer thaw depth and soil moisture content and the investigation of the relationship of these parameters to soil surface properties and soil texture
Summary
Permafrost on the Tibetan Plateau reacts very sensitively to climate change (Liu and Chen, 2000; Zhao et al, 2010). The active layer is “the layer of ground that is subject to annual thawing and freezing in areas underlain by permafrost” (van Everdingen, 1998). In this environment, it plays a significant role since almost all biogeochemical, hydrological, ecological, and pedogenic processes take place in this uppermost part of the soil (Kane et al, 1991; Hinzman et al, 2005). Important factors are surface temperature, physical and thermal properties of the surface cover and the substrate, vegetation cover, soil moisture content, albedo, and thickness and duration of snow cover (Duguay et al, 2005; Hinzman et al, 2005)
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