For example, the radiocarbon and hydrogen isotopic composition of methane from Greenland ice cores suggests that atmospheric methane rise at 11.6 and 38 ka can be predominantly accounted for through wetland emissions 14, 15. However, the role of marine gas hydrate releases in influencing atmospheric methane concentrations during the Quaternary remains uncertain. Large magnitude gas hydrate dissociation events are also proposed to have occurred in the more recent past, as evidenced by major fluid flow structures in sedimentary basins, such as pockmarks 4, 13. Methane released by the dissociation of marine gas hydrates has been inferred to be the cause of a number of negative δ 13C excursions in the geological record 6, 7. The rates and timescales over which gas hydrates dissociate control the impact of hydrate-derived methane on the global climate system. The transfer of this methane to the water column has the potential to amplify ocean acidification and de-oxygenation and, possibly, atmospheric greenhouse gas concentrations 11, 12. If bottom water warming and/or hydrostatic pressure decrease is large enough, gas hydrate dissociation and release of a significant amount of methane are possible 4, 6, 7, 8, 9, 10. Consequently, changes in the thickness of the gas hydrate stability zone (GHSZ) are likely to occur along glaciated continental margins where pressure regimes are governed by alternating glacial loading and unloading cycles, and gas hydrate dissociation may be amplified by the influx of warmer waters following ice retreat 2, 3, 4, 5. The stability of the marine gas hydrate reservoir is primarily affected by changes in temperature and hydrostatic pressure. Gas hydrates are found in a variety of geological settings 2 but are most common on continental margins where the combination of appropriate pressure–temperature conditions and the presence of organic-rich sediments are conducive to abundant methane generation. Large quantities of methane exist as free gas, dissolved in pore fluids and solid gas hydrates within marine sediments 1.

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