Ninth International Conference on Permafrost ... - IARC Research

Forcing Factors of Permafrost Retreat: A Comparison Between LGM andPresent-Day Permafrost Extent in EurasiaJef VandenbergheInstitute of Earth Sciences, VU University Amsterdam, The NetherlandsAndrei VelichkoLaboratory of Evolutionary Geography, RAS, Moscow, RussiaAldar GorbunovPermafrost Institute, SD RAS, Almaty, KazakhstanIn recent years, it has been shown that growth andespecially decay of permafrost may have tremendous effectson the environmental conditions of the concerned region.Attributing the cause for changes in permafrost occurrenceonly to global temperature changes is apparently too simple.There are a number of feedback mechanisms that potentiallymay induce regional differences in permafrost extensionor reduction. In this short note, we expand on the factorsthat have contributed to the northward displacement of thesouthern permafrost limit on the Eurasian continent sincethe last glacial maximum (LGM) and which role potentiallymay be enhanced in the near future.For that purpose we have constructed the southernmostextent of the permafrost during the LGM by combiningdifferent sources of research, and compared that with thepresent-day permafrost extent. Mapping the southern limitof permafrost is not as simple as it may look because ofseveral reasons:• LGM permafrost maps are not always distinctivein describing whether the permafrost is continuous,discontinuous, or sporadic.• Even when this distinction is made, the definitions ofthose terms are not always the same in the different papers.• The age of permafrost indicators of the LGM hasoften not precisely been defined.• The altitude plays a decisive role in permafrostdistribution, and the distinction between latitudinal andmountainous permafrost may be diffusive (French 1996).• High altitudes may shift the latitudinal permafrostlimit substantially southward.With these restrictions in mind we (re)constructed for bothperiods the location of the position of the southern limit ofpermafrost (including sporadic, island, and discontinuouspermafrost) and that of continuous permafrost (Fig. 1).For the present-day situation, we based us essentiallyon the Arctic Permafrost Map as compiled by Brown etal. (1998). In the zone of continuous permafrost, regionswith mountainous permafrost are included (e.g., in theUral Mountains and especially in eastern Siberia). TheLGM reconstruction is more complicated. For westernand central Europe, we used data published by Van Vliet(1996), Renssen & Vandenberghe (2003), Vandenberghe etFigure 1. Southern limits of modern permafrost (upper full line) and continuous permafrost (upper stippled line), and LGM permafrost (lowerfull line) and continuous permafrost (lower stippled line), largely based on Aubekerov & Gorbunov (1999), Vandenberghe et al. (2004a,b)and Velichko (2002).327