| Abstract | Permafrost influences both periglacial- and glacial processes, and is thus an important factor to consider in geomorphic studies of cold-climate areas. This becomes particularly evident as permafrost today underlies about 25 % of the Earth’s land area (French, 1996), and that extensive permafrost areas existed in ice-marginal (Lozinski 1909) and subglacial (Kleman and Hättestrand, 1999) positions of the Pleistocene ice sheets. At present, public interest in permafrost generates from the possible geomorphic response of permafrost thaw following imminent climate warming, including land subsidence and large rock slides. Permafrost thaw will also most likely increase the release of the important greenhouse gas methane, which will further enhance global warming. This thesis focuses on near ground surface temperatures and permafrost distribution at selected sites in central-eastern Norway and central Spitsbergen, Svalbard, and discusses associated geomorphic implications. In an attempt to map and model permafrost distribution in the mountains of central-eastern Norway, standard procedures including BTS measurements and DC resistivity soundings (Etzelmüller et al., 2001; Hoelzle et al., 2001) were followed. Later, however, it was shown that the assumptions behind the BTS-method may not have been fulfilled, rendering these results dubious. Other modelling techniques were therefore required. Moreover, increased knowledge on the relation between climate and permafrost is required to predict the response of the permafrost to climate change. Thus, a modelling approach considering the climate-permafrost relation directly was attempted (Smith and Riseborough 1996; 2002). The influence of air temperature, snow cover (thickness and timing), blocky debris and solar radiation was considered. A sensitivity study showed that snow cover and block fields was the most important microclimatic factors, controlling winter ground freezing, while solar radiation was of secondary importance for the distribution of permafrost in central-eastern Norway. A study of thermal processes in block fields in central-eastern Norway and in the active layer of a rock glacier on Svalbard, together with an analysis of additional data on blocky debris thermal regime provided by colleagues, showed that blocky debris provide a negative thermal anomaly as compared to bedrock and till. This anomaly makes blocky debris particularly favourable for permafrost occurrence. The anomaly is largely related to winter conditions; a good thermal coupling to the ambient air temperature, in some cases efficient air convection in the openwork pore volume, and seasonal variation in thermal conductivity if significant amounts of ice accumulate in the pores in the wintertime. The occurrence of permafrost may increase landscape denudation by reinforcing subaerial weathering and mass wasting processes (permafrost creep and solifluction). A conceptual model for rock glacier formation and development from avalanches has been developed for the investigated rock glacier in Svalbard. Here, spring avalanches tend to erode, transport and deposit rock debris. As the rock debris melts out from the avalanche snow deposits in the summer, it forms a protective cover against further melting. In this way avalanche snow may remain through the ablation season, adding to the rock glacier permafrost. The result is a layered permafrost deposit consisting of alternating layers of debris and relatively clean ice. A rock glacier forms when enough ice is present for creep to occur. Solifluction has been mapped in central-eastern Norway and shown to be primarily dependent on soil characteristics, but permafrost may be important in less favourable soil conditions. On the other hand, subglacial permafrost may inhibit glacial erosion. The block fields in central-eastern Norway have been preserved beneath at least one or two thick Pleistocene ice sheets, as revealed by incised glacial meltwater channels, perched glacial erratics and slight glacial reworking of material. |
