Why should the East Siberian Shelf be considered a new focal point for methane studies in terms of Global Climate Change?
Abstract
The inner East Siberian Arctic Shelf (ESAS) has not been considered to be a methane (CH4) source to hydrosphere or atmosphere because submarine permafrost, which underlies most of the ESAS, was believed, first, not to be conducive to methanogenesis, and, second, to be acting as an impermeable lid, preventing CH4 escape through the seabed. However, recent experimental data obtained during summer expeditions (2005-2008) on dissolved CH4 and atmospheric CH4 mixing ratio, and data on dissolved CH4 collected during a winter expedition (2007) show that extremely high concentrations of dissolved CH4 and an impulsively (non-gradually) increasing atmospheric mixing ratio of CH4 in some areas of the ESAS can be attributed to methanogenesis in taliks of different origins (exogenous, endogenous), and to year-round release through these taliks of old CH4 from seabed CH4 reservoirs. The occurrence of taliks that are not located above fault zones and/or river paleo-valleys (which mostly coincide) is not consistent with currently existing theoretical notions and modeling results on submarine permafrost thermal state, spatial extent, and the exclusive role of endogenous taliks as pathway providers for CH4 release from seabed reservoirs. It is highly likely that the role of exogenous taliks and taliks of combined origin have been significantly underestimated. It is also highly likely that the CH4 released from seabed reservoirs could be emitted by different types of decaying gas hydrates, one of which is unique relic hydrates, which occur as shallowly as 20 m below the seabed and could be disturbed by the warming of as much as 12-17°C that has occurred as the sea intruded during the last 10-15 Kyr. If submarine permafrost fails to impede CH4 emission from seabed reservoirs the modern biogeochemical cycle could be significantly altered because the extreme shallowness of the inner ESAS allows the majority of CH4 to pass through the water column and escape to the atmosphere.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.U23D0081S
- Keywords:
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- 0475 Permafrost;
- cryosphere;
- and high-latitude processes (0702;
- 0716);
- 4540 Ice mechanics and air/sea/ice exchange processes (0700;
- 0750;
- 0752;
- 0754);
- 4800 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL (0460);
- 4806 Carbon cycling (0428);
- 4835 Marine inorganic chemistry (1050)