HR: 08:00h
AN: C11A-01 INVITED     [Abstracts]
TI: The Evolution of Coastal and Offshore Permafrost During the Last Climatic Cycle in the Laptev Sea Region, Russia
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: Geocryology Department Moscow State University, Vorobyovy Gori, Moscow, 119992 Russian Federation
AB: Coastal and offshore permafrost in the Laptev Sea region have been studied during the last years within the framework of the Russian-German programmes "Laptev Sea System" and "System Laptev Sea 2000." Mathematical simulations of permafrost evolution were carried out showing that ice-bearing and ice-bonded permafrost exists presently within coastal lowlands and under the shallow shelf. Open taliks, giving pathway to methane from unstable former gas hydrates, can develop from modern and palaeo-river taliks in active fault zones and from lake taliks over fault zones or lithospheric blocks with a higher geothermal heat flux. Ice-bearing and ice-bonded permafrost in the northern regions of lowlands and in the inner shelf zone, have been preserved during at least four Pleistocene climatic and glacial-eustatic cycles. Presently, they are subjected to degradation from the bottom under the impact of geothermal heat flux. In addition to the development of permafrost during the last glacial cycles the processes causing coastal erosion and changing the permafrost topography before and during the Holocene transgression of the shelf will be shown. About 13 kyr BP thermokarst started to destroy the so called Ice Complex (IC) both on the shelf and coastal lowlands. Thermokarst lakes and depressions were formed (11-11.5)-(9.5-8.5) kyr BP when the position of the shoreline was at the actual isobathes -60;-45 m. Thermokarst processes started before the submergence of the shelf by sea water with negative temperature. Due to the transgression, thermokarst lakes and alases with a bottom level below the actual sea level particulary on the shallow part of the shelf (between isobath - 20 m and the recent shoreline) were transformed into ,thermokarst lagoons". On the Bykovsky Peninsula and the vast areas eastward from the Yana river delta this process still occurs today and the resulting relief types can be found in the field. The formation of ,thermokarst lagoons" resulted in the formation of a irregular coastline, an increase of shores length subjected to thermoerosion, especially after 7.5 kyr BP.
DE: 1815 Erosion and sedimentation
DE: 1823 Frozen ground
SC: Cryosphere [C]
MN: 2004 AGU Fall Meeting