1 Review Article: Permafrost Trapped Natural Gas in 1 Svalbard, Norway 2 Authors: Thomas Birchall* 1, 2 , Malte Jochmann 1, 3 , Peter Betlem 1, 2 , Kim Senger 1 , Andrew 3 Hodson 1 , Snorre Olaussen 1 4 1 Department of Arctic Geology, The University Centre in Svalbard, P.O. Box 156, N-9171 Longyearbyen, 5 Svalbard, Norway 6 2 Department of Geosciences, University of Oslo, P.O. Box 1047, Blindern, 0316 Oslo, Norway 7 3 Store Norske Spitsbergen Kulkompani AS, Vei 610 2, 9170 Longyearbyen, Svalbard. Norway 8 *Correspondence to: Thomas Birchall (Thomas.birchall@unis.no) 9 10 Abstract. Permafrost has become an increasingly important subject in the High Arctic archipelago of Svalbard. 11 However, whilst the uppermost permafrost intervals have been well studied, the processes at its base and the 12 impacts of the underlying geology have been largely overlooked. More than a century of coal, hydrocarbon and 13 scientific drilling through the permafrost interval shows that accumulations of natural gas trapped at the base 14 permafrost is common. They exist throughout Svalbard in several stratigraphic intervals and show both 15 thermogenic and biogenic origins. These accumulations combined with the relatively young permafrost age 16 indicate gas migration, driven by isostatic rebound, is presently ongoing throughout Svalbard. The accumulation 17 sizes are uncertain, but one case demonstrably produced several million cubic metres of gas over eight years. Gas 18 encountered in two boreholes on the island of Hopen appears to be situated in the gas hydrate stability zone and 19 thusly extremely voluminous. While permafrost is demonstrably ice-saturated and acting as seal to gas in 20 lowland areas, in the highlands it appears to be more complex, and often dry and permeable. Svalbard shares a 21 similar geological and glacial history with much of the Circum-Arctic meaning that sub-permafrost gas 22 accumulations are regionally common. With permafrost thawing in arctic regions, there is a risk that the impacts 23 of releasing of sub-permafrost trapped methane is largely overlooked when assessing positive climatic feedback 24 effects. 25 26 Keywords 27 Permafrost; Top seal; Natural Gas; Cryosphere; Greenhouse Gas; Arctic; Greenhouse Gas; Hydrates. 28 29 https://doi.org/10.5194/tc-2021-226 Preprint. Discussion started: 9 August 2021 c  Author(s) 2021. CC BY 4.0 License.