| Summary: | In the cold regions of the Earth, a continuous cover of permafrost characterizes the nonglaciated parts of the landscape. The permafrost layer separates hydrological processes into the near-surface and deep (subpermafrost) hydrological systems. Together with glaciers and ice sheets, the permafrost seals the deep groundwater system and solutes such as greenhouse gases produced in the deep subsurface. The subject of this PhD thesis is groundwater springs in continuous permafrost regions that are found above perennially unfrozen zones of the ground. These so-called talik springs form exceptional links for subpermafrost groundwater and solutes to reach the surface and atmosphere. Since they are most often located in lowlying Arctic valleys, such valleys served as the field areas of the PhD study. The four research papers included in this PhD thesis address some of the unresolved questions about the driving mechanisms behind talik springs and the landscape features that favor their formation. The first two research papers were motivated by an apparent lack of recharge sources to subpermafrost groundwater systems in some of the areas with talik springs. In Paper I, a conceptual model for talik springs driven by millennial-scale permafrost aggradation was developed in response to this apparent hydrological imbalance. The principal idea is that the expansion of water upon freezing can generate the sufficient hydraulic pressures to drive groundwater flow and talik spring discharge. The conceptual model was investigated through numerical modelling experiments in Papers I and II. The modelling experiments in Paper I used a sequential modelling scheme with separate simulations of heat transfer and groundwater flow and were based on field observations from Adventdalen, Svalbard. With the results from this first modelling study, we show that the proposed conceptual model does indeed represent a feasible mechanism for driving talik springs. In Paper II, a numerical model with increased process complexity was applied to ...
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