Ground Dynamics in the Norwegian Periglacial Environment Investigated by Synthetic Aperture Radar Interferometry

Abstract

Cold polar and mountainous periglacial environments are characterised by highly dynamic ground surfaces that move under the action of frost and gravity, and contribute to shaping the landscape. The movement rates and directions are spatially and temporally variable, depending on the involved periglacial processes and their environmental controlling factors. Spaceborne Synthetic Aperture Radar (SAR) has revolutionised the investigation of the ground surface in polar and mountainous regions, due to its ability to image large and remote areas independently of light and meteorological conditions. By comparing images taken at different times, the SAR Interferometry (InSAR) technique can remotely detect ground surface displacements at centimetre to millimetre accuracy. This thesis exploits the InSAR technology to analyse the spatial distribution and temporal variability of the ground surface displacements in periglacial environments. The spatio-temporal displacement patterns are documented on a regional scale, allowing for the study of the kinematic signatures of various frost- and gravity-driven processes. The research takes advantage of the Copernicus Sentinel-1 SAR mission that provides open access images with unprecedented spatial coverage and at a weekly temporal resolution. Sentinel-1 InSAR is complemented with results based on the high spatial resolution TerraSAR-X images. The advantages and limitations of InSAR in the scope of periglacial research are discussed based on case studies in central and western Spitsbergen (Svalbard) and in Troms and Finnmark (Northern Norway). In Papers I–V, we demonstrate the ability of InSAR to document the kinematic properties of the periglacial ground dynamics, characterised by displacement rates ranging from a millimetre to a metre over a season or a year. InSAR allows for investigating the displacement progression caused by the ground freeze–thaw cycles in permafrost lowlands and the gradual downslope creep of periglacial landforms in mountainous environments. InSAR observations are compared with in-situ measurements and geomorphological mapping, and coupled with statistical and physical modelling. This integration contributes to a better understanding of the factors controlling the spatio-temporal patterns of the ground movement. This research suggests novel ways to develop dedicated InSAR products relevant for the assessment of geohazards and the systematic observation of ground dynamics in the context of climate change. The results show the value of combining satellite InSAR with complementary remote sensing techniques to document fast-moving landforms and provide decadal time series. Finally, this dissertation outlines perspectives for furthering the work in the scope of InSAR applied to periglacial research.