GPR is applied to image subsurface structures below non-sorted polygons in Kapp Linné, Svalbard, where ice and active-layer soil wedges co-exist within a small area. Two-dimensional GPR images ice wedges as hyperbolic reflections extending down from the frost table. However, some ice-wedge signals are obscured or masked by similar hyperbolic reflections produced by stones or active-layer soil wedges. Three-dimensional GPR images ice wedges as linear amplitude anomalies, which excludes the possibility of misinterpretation and offers more reliable results. GPR investigations show that ice wedges are distributed sporadically in lower (younger) beach ridges, but not in higher (older) ones.
Inter-site monitoring of ground temperature, soil moisture, slow ground deformation and cracking during 2004–09 and the determination of near-surface soil texture and stratigraphy suggest that snow cover and soil thermal properties determine the distribution of ice wedges. Most ice wedges are considered to be inactive due to relatively high permafrost temperatures. Shock loggers and extensometers detected shallow (soil wedge) cracking in sandy sediments, when the ground surface temperature dropped to −12°C and the thermal gradient in the upper 20 cm of ground reached −10°C m−1. Copyright © 2013 John Wiley & Sons, Ltd.