Ninth International Conference on Permafrost ... - IARC Research

Ni n t h In t e r n at i o n a l Co n f e r e n c e o n Pe r m a f r o s tal. (2004b); for Russia, maps provided by Velichko (2002);for Kazakhstan, a map by Aubekerov & Gorbunov (1999);and for China, data compiled from different sources (e.g.,Vandenberghe et al. 2004a). Especially in regions where theboundary between discontinuous and continuous permafrostis crossing mountainous areas, the zone of discontinuous andsporadic permafrost may be very limited in extent and, assuch, not exactly defined in the published literature. For theLGM situation, this is the case, for instance, in the southernCentral Massif (France), the southern Carpathians, and thesouthern margin of the Tibetan Plateau.A few striking results appear from the comparison betweenLGM and present-day permafrost extension limits. Wederive a general, extremely constant west–east orientationof the permafrost boundary during the LGM at around 52°Nlatitude in lowlands, apart from minor expulsions to the southin upland regions (e.g., Central Massif, Carpathians) and amajor southward expulsion due to the mountain permafrostof the Tibetan Plateau. This is in line with the zonal extensionof permafrost reported by Huijzer and Vandenberghe (1998)for west and central Europe and by Velichko (1973) forsouthern Russia. It may be explained by the combined coldsources of sea ice and ice sheets in the North Atlantic Ocean,Arctic Sea, northern Europe, and Siberia. Tracks of westerlywinds were shifted towards the south and, in any case, werenot able to induce maritime influences on the continent at thelatitude of permafrost occurrence (Isarin & Renssen 1999,Renssen & Vandenberghe 2003).The present-day situation shows a distribution pattern thatsignificantly differs from the LGM pattern. The southernlimit of permafrost shows a clear shift to the south fromc. 69°N latitude south of Nova Zembla to 66° in westSiberia and 61° in east Siberia (around the Lena River). Thelatitudinal permafrost occurrence in easternmost Siberiais difficult to determine because of the interference withaltitudinal permafrost. This Eurasian permafrost extension isobviously directed by the cold Arctic Sea, while there is nosteering at all by North Atlantic sea ice. Maritime influences,through westerlies that transport temperate air from theNorth Atlantic waters, are diminishing towards the east. Onthe contrary, warm equatorial waters are entering the NorthAtlantic Ocean at present by the Gulf Stream.Thus, both the temperatures over the North Atlantic andthe Arctic Sea determine the extent of permafrost overEurasia. During the LGM the cold (frozen) North AtlanticOcean and Arctic Sea induced the regular zonal pattern withoverall west–east oriented permafrost limit. By now theNorth Atlantic Ocean change to warmer conditions induceda northward shift of the permafrost limit over Europe, whichis gradually disappearing eastward over Siberia.Brown, J., Ferrians, O.J., Jr., Heginbottom, J.A. & Melnikov.E.S. 1998. Revised February 2001. Circum-ArcticMap of Permafrost and Ground-Ice Conditions.Boulder, CO: National Snow and Ice Data Center/World Data Center for Glaciology. Digital Media.French, H.M. 1996. The Periglacial Environment, 2nd ed.),Edinburgh Gate: Addison Wesley Longman.Huijzer, A.S. & Vandenberghe, J. 1998. Climaticreconstruction of the Weichselian Pleniglacialin north-western and central Europe. Journal ofQuaternary Science 13: 391-417.Isarin, R.F.B. & Renssen, H. 1999. Reconstructing andmodelling Late Weichselian climates: the YoungerDryas in Europe as a case study. Earth Sci. Rev. 48:1-38.Renssen, H. & Vandenberghe, J. 2003. Investigation of therelationship between permafrost distribution in NWEurope and extensive winter sea-ice cover in theNorth Atlantic Ocean during the cold phases of theLast Glaciation. Quaternary Science Reviews 22:209-223.Vandenberghe, J., Cui, Z.J., Zhao, L. & Zhang W. 2004a.Thermal contraction crack networks as evidencefor Late-Pleistocene permafrost in Inner Mongolia.Permafrost and Periglacial Processes 15: 21-29.Vandenberghe, J., Lowe, J., Coope, G.R., Litt, T. & Zöller,L. 2004b. Climatic and environmental variabilityin the Mid-Latitude Europe sector during the lastinterglacial-glacial cycle. In: R. Battarbee, F. Gasse,& C. Stickley (eds.), Past Climate Variability throughEurope and Africa: PEPIII <strong>Conference</strong> Proceedings.Dordrecht: Kluwer, 393-416.Van Vliet-Lanoë, B. 1996. Relations entre la contractionthermique des sols en Europe du Nord-Ouest et ladynamique de l’ínlandsis Weichsélien. ComptesRendus Académie des Sciences de Paris 322, sérieIIa: 461-468.Velichko, A.A. 1973. Paragenesis of a cryogenic (periglacial)zone. Biuletyn Peryglacjalny 7: 89-110.Velichko, A.A. 2002. Dynamics of terrestrial landscapecomponents and inner marine basins of NorthernEurasia during the last 130,000 years. A.A. Velichko(ed.-in-chief). Moscow: GEOS Publishing House,231 pp. (in Russian).ReferencesAubekerov, B. & Gorbunov, A. 1999. Quaternary permafrostand mountain glaciation in Kazakhstan. Permafrostand Periglacial Processes 10: 65-80.328