Did anyone on the list attend this EGU ESAS methane session? If not, has anyone seen relevant coverage or picked up any related information? I know this topic is of great interest to many group members, myself included.
Josh Horton On Tuesday, April 17, 2012 7:17:10 AM UTC-4, andrewjlockley wrote: > > > http://arctic-news.blogspot.co.uk/2012/04/highlights-of-egu-general-assembly-2012.html?m=1 > > Highlights of EGU General Assembly 2012 > > If you will be attending the European Geosciences Union (EGU) General > Assembly on April 25, 2012, make sure to attend, from 14:00 to 14:15 in > room 23, the presentation: > > Methane release from the East-Siberian Arctic Shelf and its connection > with permafrost and hydrate destabilization: First results and potential > future developments by Natalia Shakhova and Igor Semiletov > > The East Siberian Arctic Shelf (ESAS) is home to the world’s largest > hydrocarbon stocks, which consist of natural gas, coal bed methane (CH4), > and shallow Arctic hydrates. Until recently, the ESAS was not considered a > CH4 source due to the supposed impermeability of sub-sea permafrost, which > was thought to completely isolate the CH4 beneath from modern > biogeochemical cycles. > > However, the ESAS represents an enormous potential CH4 source that could > be responsive to ongoing global warming. Such response could occur in > substantially shorter time than that of terrestrial Arctic ecosystems, > because sub-sea permafrost has experienced long-lasting destabilization > initiated by its inundation during the Holocene ocean transgression. ESAS > permafrost stability and integrity is key to whether sequestered ancient > carbon escapes as the potent greenhouse gas CH4. > > Recent data suggest the sub-sea permafrost is currently experiencing > significant changes in its thermal regime. For example, our recent data > obtained in the ESAS during the drilling expedition of 2011 showed no > frozen sediments at all within the 53 m long drilling core at water > temperatures varying from -0.6˚C to -1.3˚C. > > Unfrozen sediments provide multiple potential CH4 migration pathways. We > suggest that open taliks have formed beneath the areas underlain or > influenced by the nearby occurrence of fault zones, under paleo-valleys, and > beneath thaw lakes submerged several thousand years ago during the ocean > transgression. Temporary gas migration pathways might occur subsequent to > seismic and tectonic activity in an area, due to sediment settlement and > subsidence; hydrates could destabilize due to development of > thermokarst-related features or ice-scouring. > > Recently obtained geophysical data identified numerous gas seeps, mostly > above prominent reflectors, and the ubiquitous occurrence of shallow > gas-charged sediments containing numerous gas chimneys, underscoring the > likelihood that the ability of sub-sea permafrost to capture CH4 released > from the seabed is failing. > > Available data suggest the ESAS sub-sea permafrost is currently leaking a > substantial amount of CH4. We propose that a few different types of CH4 > exist, and are becoming involved in the modern carbon cycle due to > permafrost destabilization in the ESAS: modern biogenic CH4 produced from > ancient substrate, relatively old biogenic CH4 mobilized from hydrate > deposits, and old thermogenic CH4 accumulated within seabed deposits. > Isotopic data obtained by sampling CH4 in the water column and atmospheric > CH4 in close proximity to the sea surface confirm the contribution from > different sources, and demonstrate that the isotopic signature of CH4 from > the ESAS can be used to create an interpretive plot for defining hydrates. > CH4 fluxes could occur as numerous weak seeps, as large areas of strong > bubble plumes, or as sites where CH4 releases are flare- or torch-like and > the emissions are non-gradual. > > Due to the shallow and oligotrophic nature of the ESAS, the majority of > aqueous CH4 may avoid biological oxidation in the water column and escape > to the atmosphere. > > Further investigations should be focused on quantifying the total CH4 pool > of the ESAS, improving our understanding of the mechanisms responsible for > sub-sea permafrost destabilization and gas migration pathways formation, > and decreasing uncertainties regarding the current CH4 emission mode and > its future alteration by progressing permafrost degradation. > > Geophysical Research Abstracts Vol. 14, EGU2012-3877-1, 2012 EGU General > Assembly 2012 > > Above presentation is part of the session: Methane cycling in marine and > terrestrial systems which also features, as part of the poster program: > Display Time: Wednesday, 25 Apr 08:00–19:30 Attendance Time: Wednesday, 25 > Apr 17:30–19:00 Poster Area BG > > First drilling subsea permafrost in the southeastern Laptev Sea, the East > Siberian Arctic Shelf: results and challenges by Igor Semiletov, et al. > highlighting the following two challenges: > > 1) observed Arctic warming in early 21st century is stronger than > predicted by several degrees, which may accelerate thaw release of methane > from the upper seafloor layer by increasing bottom erosion and from deeper > stratums (including hydrates) by sediment settlement and adjustment; > > 2) drastic sea ice shrinkage causes increase in storm activities and > deepening of the wind-wave-mixing layer down to depth ~50 m that enhance > methane release from the water column to the atmosphere. > > Geophysical Research Abstracts Vol. 14, EGU2012-3913, 2012 EGU General > Assembly 2012 > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. 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