Dr. Henry Patton - Ice sheet-gas hydrate interactions techniques

Résumé / Abstract

Large amounts of the potent greenhouse gas methane are stored across the Arctic as gas hydrate; one cubic metre of this ice-like, solid mixture of gas and water contains c. 160 m3 of free gas. Hydrates are stable under low temperature and high pressure conditions, small changes in which can trigger large-scale methane release. During past ice ages, the storage of methane as gas hydrates was much more extensive, with conditions beneath the vast ice sheets ideal for the formation of thick, stable gas hydrate reservoirs. The post-glacial destabilisation of these shallow carbon reservoirs, which is still ongoing today, triggered mega-submarine landslides and tsunamis (e.g., Storegga), ocean acidification, and global atmospheric warming events (“clathrate-gun”). Furthermore, the mechanisms and effects of such widespread hydrate dissociation are relevant for similar reservoirs inferred to exist beneath today’s Antarctic and Greenland ice sheets. We combine state-of-the-art marine geophysics with high-resolution ice-sheet/hydrate modelling to study how the advance and retreat of successive ice sheets in the Eurasian Arctic has influenced methane storage and release, and conversely how subglacial gas hydrate formation has influenced ice sheet dynamics. Case studies that will be discussed include: kilometre-scale seafloor craters in the central Barents Sea, inferred to have formed by catastrophic methane gas release from destabilizing gas hydrate reservoirs post deglaciation; and the formation of high basal traction “sticky spots” that regulate fast ice flow, created from the desiccation of subglacial sediments during hydrate formation.