HR: 0800h
AN: C11A-1058    [Abstracts]
TI: The Long-term Dynamics of Permafrost and the Gas Hydrate Stability Zone in Rift Structures of the Shelf of the Seas of Eastern Eurasia
AU: * Hubberten, H W
EM: hubbert@awi-potsdam.de
AF: Alfred Wegener Institute for Polar and Marine Research, Telegrafenberg A 43, Potsdam, 14473 Germany
AU: Romanovskii, N N
EM: nromanovsky@online-ru
AF: Moscow State University Geology Department, Vorobyovy Gory, Moscow, 119899 Russian Federation
AU: Eliseeva, A A
C11A-1058 AF: Institute of Geoecology RAS, Leninskii Prospect, Moscow, 117071 Russian Federation
AU: Tipenko, G S
C11A-1058 AF: Moscow State University Mathematics and Mechanics Department, Vorobyovy Gory, Moscow, 119899 Russian Federation
AB: In Eurasian Arctic shelf areas, especially those of the Kara, Laptev and East Siberia Seas, the occurrence of submarine permafrost and gas hydrates are characteristic features. In some of the shelf areas oceanic rift zones stretch to the continent, as for example in the Laptev Sea area where the Gakkel Ridge continues to the land. Great differences in geothermal heat flow values and in the properties of the sediments and rocks have to bee assumed in undisturbed block of the lithosphere and in fault zones in this region just as in continental rifts (such as Momskii and Baikalskii rifts, etc.). As a result differences in the thickness of permafrost and the gas hydrate stability zone (GHSZ) within these structures are expected. The thickness of permafrost and the GHSZ change essentially and irregularly in the stages of regressions and transgressions of the sea. For the investigation of permafrost and GHSZ evolution, and their long-term dynamic and interaction in rift structures a two - dimensional mathematical models have been elaborated. The paleogeographic scenario used in this calculation covers the time from middle - late Pleistocene to the Holocene (c. 400 kyr), i.e. the last four climatic and glacio-eustatic cycles. Model calculations for rift structures of different sizes, and different heat flow values, which are typical for a different geographic situation on the shelf and as the result have a different paleogeographic history have been carried out. Simulations have been made for fault zones being 20, 10 and 5 km wide, and for single faults from some hundred meters to 1 km in width situated on the shelf at latitudes from 710 to 760 N which reflects the zonation of the mean annual ground temperature during regression periods. The modeling results show, that the thickness of offshore permafrost in the stages of climatic warming and transgressions essentially decrease however, rather irregular. The permafrost thickness is essentially more reduced in fault zones, than in the consolidated blocks with lower heat flow values. Similar processes take place with the thickness variation of the GHSZ as well. Variations in the thickness of permafrost and the GHSZ depend on fault zones, single faults sizes and heat flow values. For example, at recent time an open talik and a 'break' in the GHSZ exist under a 20 km wide fault zone at heat flow of 100 mW/m2, but they do not form under a only 5 km wide fault zone at the same heat flow. According to the results of the simulations, a first estimation of the regularities of permafrost and GHSZ thickness variation has been carried out. The possibilities and the boundary conditions for the occurrence of both: 1-open taliks and "breaks" in the GHSZ , which may result in an emission of greenhouse gases from relic sub-permafrost layers, and 2- anticline like structures which may work as traps for sub-permafrost gases and hydrates, have been estimated.
DE: 0700 CRYOSPHERE (4540)
DE: 0702 Permafrost (0475)
DE: 0714 Clathrate
DE: 0768 Thermal regime
DE: 0798 Modeling
SC: Cryosphere [C]
MN: Fall Meeting 2005