Quantifying the dynamic response of permafrost and slope stability to a changing climate

• Main Author: Mithan, Huw
• Format: Thesis
• Language: English
• Published: 2018
• Subjects: G Geography (General); GA Mathematical geography. Cartography; GB Physical geography; GE Environmental Sciences; Arctic; Svalbard; Ice; permafrost; Alaska
• Online Access: https://orca.cardiff.ac.uk/id/eprint/111329/; https://orca.cardiff.ac.uk/id/eprint/111329/13/111329%20dec%20page%20removed.pdf; https://orca.cardiff.ac.uk/id/eprint/111329/2/mithanht.pdf

The Arctic contains a wealth of landforms that are governed by the diurnal and seasonal response of permafrost to climatic and topographic forcings. Of key importance to the process rates of many periglacial landforms is the dynamic behaviour of the active layer, which regulates the transfer of heat and moisture between the atmosphere and permafrost. The strong dependence of periglacial process rates on active layer dynamics makes this geomorphic system particularly sensitive to future increases in Arctic temperatures and precipitation. These increases will continue to degrade permafrost, affecting the distribution and rates of periglacial processes. I develop a landform classification model on Svalbard that reveals solifluction and scree to be the most dominant hillslope processes acting on this landscape, with sediment fluxes greatest in solifluction. A combination of landslide mapping, solifluction modelling and slope stability analysis in Alaska reveals that landslides are coincident with convergent topography on soliflucting hillslopes that have concentrated ground ice at depth. Convergent topography allows for higher moisture availability that feeds the growth, concentration, and development of a large network of ice lenses at the permafrost/active layer boundary. The excess pore pressures generated upon thaw reduces the shear strength of soil at the base of the active layer, causing it to slide downslope along a planar slip surface on top of the unthawed permafrost. Due to a warming Arctic, permafrost is expected to continue thawing, creating an ever more dynamic and deeper active layer. Consequently, the relative regional extent of periglacial landforms in mountainous Arctic environments is expected to change, with Arctic hillslopes becoming more unstable during extreme summer thawing. This will pose a greater hazard to Arctic infrastructure and act as a major force for environmental and geomorphological change.