Ice‐wedge polygon dynamics in Svalbard: Lessons from a decade of automated multi‐sensor monitoring

• Published in: Permafrost and Periglacial Processes
• Main Authors: Matsuoka, Norikazu, Christiansen, Hanne H., Watanabe, Tatsuya
• Other Authors: Japan Society for the Promotion of Science
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 2018
• Subjects: Svalbard; Ice; permafrost; Permafrost and Periglacial Processes; wedge*
• Online Access: http://dx.doi.org/10.1002/ppp.1985; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1002%2Fppp.1985; http://api.wiley.com/onlinelibrary/chorus/v1/articles/10.1002%2Fppp.1985; https://onlinelibrary.wiley.com/doi/pdf/10.1002/ppp.1985

Abstract Twelve years of continuous monitoring of diverse ground properties reveals the dynamics of three ice wedges and adjacent ground in a low‐centered polygon area in Svalbard. The monitoring documented ground displacements, the timing of crack generation, ground thermal and moisture conditions from the surface to the top permafrost, and snow conditions. The focus is on seasonal ground deformation in and around ice‐wedge troughs, interannual variability of ice‐wedge activity and thermal thresholds for ice‐wedge cracking. Seasonal ice‐wedge activity is mainly associated with frost heave and thaw settlement, as well as thermal expansion and contraction. In mid‐ to late winter, temporary expansion and cracking of troughs by thermal contraction occurs during rapid cooling periods. Following intensive ground microcracking events, troughs show rapid expansion and in some cases major cracking in the frozen active layer. A common threshold for cracking is identified by a combination of ground surface cooling below −20°C and a thermal gradient steeper than −10°C m −1 in the upper meter of ground, indicating that cracking requires both a brittle frozen layer and rapid ground cooling. Our results highlight that in marginal thermal conditions for ice‐wedge activity, the primary control on ice‐wedge cracking is rapid winter cooling enhanced by minimum snow cover.