2 Farbrot, Herman 2007 Department of Geosciences Oslo University of Oslo 61 Mountain permafrost, periglacial geomorphology, permafrost temperatures, permafrost mapping Mountain permafrost is an important part of the cryosphere affecting geomorphological processes and geotechnical properties of the ground. Furthermore, as permafrost is thermally defined, it is principally a climate indicator. Hence, knowledge of the distribution of mountain permafrost is important. This thesis contributes in this respect by providing insight to the permafrost distribution in Iceland and northern Norway. In Iceland mountain permafrost seems to be common above elevations of ~800-900 m a.s.l. However, the common warm weather events during winter, often make the snow cover isothermal thereby preventing permafrost occurrences at regularly snow covered sites. A regional permafrost model for Iceland based on meteorological data indicates that the permafrost region covers about 8% of the land area. In comparison glaciers cover about 11% of the land surface. In Gaissane Mountains, northern Norway, mountain permafrost is common above 350-450 m a.s.l. The more continental setting compared to Iceland with lower precipitation rates and general lack of mild weather during winter, makes the permafrost presumably less scattered within this region. In both areas permafrost is more extensively distributed than earlier recognized. Iceland is located where the asthenospheric flow under the Mid-Atlantic Ridge interacts and mixes with a deep-seated mantle plume. This implies a highly heterogeneous geothermal pattern of generally high heat fluxes especially within the Volcanic Rift Zone. To address the hypothesis of wide-spread mountain permafrost in Iceland, four shallow boreholes, situated at the inferred regional lower limit of mountain permafrost (~900 m a.s.l.), were equipped to continuously record ground temperatures. Permafrost is present at three of the four boreholes, and permafrost temperatures range from -2° to 0°C. The ground temperature profiles are non-linear, with near-surface temperature perturbations considered to relate to recent warming of the ground surface. At the non-permafrost site the insulating influence of winter snow cover is more pronounced. The limited permafrost thicknesses are related to the general high geothermal heat fluxes in Iceland, while the occurrences are controlled by air temperatures and snow cover. The results of a 1-D heat modelling approach indicate that the permafrost will degrade at these sites on the order of decades depending on climate scenarios chosen and initial subsurface ice content. Active rock glaciers are generally regarded as permafrost expressions. In Iceland, however, glacier-derived features have previously been decoupled from the permafrost realm. This view is contradicted by results presented in this thesis from similar rock glaciers in Tröllaskagi, northern Iceland. Further, the investigations indicate that glacier-derived rock glaciers develop in highly active geomorphic environments at the foot of steep, northerly exposed rock faces where snow accumulates from snow avalanches and wind drift by prevailing southerly winter winds. In the western parts of Spitsbergen, Svalbard, some large rock glaciers with a complex surface topography are situated. In order to investigate the composition and internal structures of one of these rock glaciers, the feature was surveyed with DC resistivity tomography and ground penetrating radar. The geophysical results indicate ice-rich subsurface conditions. A few continuous radargram reflectors are present, but the overall picture is a chaotic structural pattern in contrast to results from simpler lobe-shaped and tongue-shaped rock glaciers in Svalbard. This might reflect the apparent complex history of the investigated rock glacier associated with its probable Weichselian age. Furthermore, the investigations combined with previous surface displacement measurements indicate that the apparent standstill of the rock glacier is due to low ground temperatures and the low-gradient situation in which the rock glacier flows onto the strandflat.