Line Rouyet

Title of the thesis:

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

Popular scientific abstract:

In polar and mountainous regions, the cold climate leads to temperature fluctuations around 0 °C. The ground freezes and thaws, which causes upward and downward superficial movement due to the transition between water and ice. In inclined terrain, rocks and unconsolidated deposits tend to move downslope under the effect of gravity. These processes impact the terrain stability and can pose a hazard for population and infrastructure. Climatic, geologic and topographic factors control the variable distribution and timing of processes driven by frost and gravity, which determine the characteristics of the ground dynamics. However, the interactions between the environmental variables and the ground properties are complex and challenging to study.

The availability of extensive and frequent satellite imagery provides a valuable tool to enlarge the investigation in hard-to-access polar and mountainous regions. This thesis takes advantage of the open access images acquired by the Copernicus Sentinel-1 Synthetic Aperture Radar (SAR) satellites to analyse selected study areas in Northern Norway and Svalbard. The SAR Interferometry (InSAR) technique allows for measuring displacements at centimetre to millimetre accuracy, by comparing images taken at different times. The detected displacements are studied in relation to other datasets, such as temperature measurements and field-based maps.

The results show that InSAR is able to investigate the behaviour of moving landforms characterised by displacement rates ranging from a millimetre to a metre over a season or a year. InSAR can also be utilised to investigate the processes causing ground movement, and understand their relationship with environmental factors, such as the temperature and the ground composition. This thesis highlights the potential for future exploitation of InSAR technology to improve our understanding of the processes shaping cold-climate landscapes, for identifying hazardous landforms at the regional scale and monitoring the evolution of arctic environments under climate change.

The thesis is published and available in Munin (link).

Supervisors:

• Professor Anders Schomacker, Department of Geosciences, UiT (main supervisor)
• Professor Hanne Hvidtfeldt Christiansen, UNIS
• Dr. Tom Rune Lauknes, NORCE
• Dr. Lars Harald Blikra, Norwegian Water Resources and Energy Directorate

Evaluation Committee:

• Dr. Annett Bartsch, b.geos, Austria (1. opponent)
• Associate Professor Gonçalo Vieira, University of Lisbon, Portugal (2. opponent)
• Professor Helena Alexanderson, Department of Geosciences, UiT (internal member and leader of the committee)

Leader of the public defence and opposition ex auditorio:

The leader of the public defence is Professor Alfred Hanssen, Vice Dean of Innovation at Faculty of Science and Technology. If you have any questions for the candidate during the public defence, please send an e-mail to alfred.hanssen@uit.no. He will announce your questions during the defence.

Trial lecture:

Line Rouyet will hold her trial lecture on the announced topic for the PhD degree in Science on September 10 2021 at 10.15 in the same auditorium.

Title of the trial lecture:

«The Holocene evolution of mountain periglacial environments»

Streaming:

The trial lecture and the public defence will be streamed from this link

Audience:

UiT follows the national guidelines regarding infection control. A maximum of 31 people are allowed in the auditorium during the defence, as long as everybody keeps a distance of 1 meter at all times.