Methane hydrate is an ice-like substance that is stable at high-pressure and low temperature in continental margin sediments. Since the discovery of a large number of gas flares at the landward termination of the gas hydrate stability zone off Svalbard, there has been concern that warming bottom waters have started to dissociate large amounts of gas hydrate and that the resulting methane release may possibly accelerate global warming. Here, we can corroborate that hydrates play a role in the observed seepage of gas, but we present evidence that seepage off Svalbard has been ongoing for at least three thousand years and that seasonal fluctuations of 1-2°C in the bottom-water temperature cause periodic gas hydrate formation and dissociation, which focus seepage at the observed sites.

Supplement to: Berndt, Christian; Feseker, Tomas; Treude, Tina; Krastel, Sebastian; Liebetrau, Volker; Niemann, Helge; Bertics, Victoria J; Dumke, Ines; Dünnbier, Karolin; Ferre, Benedicte; Graves, Carolyn; Gross, Felix; Hissmann, Karen; Hühnerbach, Veit; Krause, Stefan; Lieser, Kathrin; Schauer, Jürgen; Steinle, Lea (2014): Temporal constraints on hydrate-controlled methane seepage off Svalbard. Published Online January 2 2014, Science