• The role of environmental factors in regional and local scale variability in permafrost thermal regime

      Cable, William Lambert; Romanovsky, Vladimir E.; Christiansen, Hanne H.; Elberling, Bo; Yoshikawa, Kenji (2016-08)
      Global climate change is a topic of great concern and research interest because there are still many components of the Earth System which we do not fully understand and cannot predict how they will respond to this change. One of these components is the permafrost that underlies approximately 24% of the Northern Hemisphere land surface. Permafrost is a thermal condition, found primarily at higher latitudes and elevations, in which subsurface material remains below 0 °C for at least two, but often up to thousands of years. As such, permafrost can accumulate large amounts of carbon in the form of organic material that remains frozen, unavailable for decomposition. However, as the climate warms, permafrost warms and thaws, slowly making this stored carbon available for decomposition into greenhouse gases, which have the potential to create a large positive feedback to climatic warming. A major challenge in permafrost research is that it is not possible to directly obtain spatial information about permafrost through remote sensing alone. This means that we must infer the presence or absence of permafrost and its thermal state based on other remotely sensible parameters such as vegetation, land surface temperature, and topography using a combination of modelling and remote sensing. To do this, we must understand the effects of different environmental factors, such as vegetation, hydrology, topography, and snow on the ground thermal regime and permafrost. In this thesis, the effects of these environmental factors are examined in relation to permafrost presence or absence and the ground thermal regime on a regional and local scale. The regional scale study focuses on the use of vegetation communities, ecotypes, as integrators of variation in environmental factors to influence the ground thermal regime. At the local scale, the microtopography created by ice-wedge polygons is examined as a cause of variations in environmental factors and the impact this has on the permafrost thermal regime of these features. We find that at both scales, remotely sensible parameters such as ecotypes and microtopography show great promise in the efforts to scale-up both field measurements and modelling results.