Holocene permafrost aggradation in Svalbard
The distribution and dynamics of permafrost represent a complex problem, confounded by a short research history and a limited number of deep vertical temperature profiles. This lack of knowledge is pronounced for the High Arctic, where most permafrost is found and where amplified responses to various climatic forcing mechanisms are expected. Within the High Arctic, the Svalbard region displays a unique climatic sensitivity and knowledge of Holocene, and modern permafrost dynamics in this region therefore have special interest. This paper reviews knowledge on Holocene permafrost development in Svalbard and the climatic background for this. In Svalbard, modern permafrost thickness ranges from less than 100 m near the coasts to more than 500 m in the highlands. Ground ice is present as rock glaciers, as ice-cored moraines, buried glacial ice, and in pingos and ice wedges in major valleys. Svalbard is characterized by ongoing local-scale twentieth-century permafrost aggradation, even though a distinct temperature increase around 1920 introduced relatively unfavourable climatic conditions for permafrost in Svalbard. Modern permafrost aggradation is to a large extent controlled by wind, solid precipitation and avalanche activity, and exemplifies the complexity of relating climate and permafrost dynamics.