Holocene Paleohydrology and Paleoclimate at Treeline, North-Central Russia, Inferred from Oxygen Isotope Records in Lake Sediment Cellulose Brent B. Wolfe, Thomas W. D. Edwards, 1 and Ramon Aravena Department of Earth Sciences and Quaternary Sciences Institute, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 Steven L. Forman Department of Earth and Environmental Sciences, University of Illinois at Chicago, 845 West Taylor Street, Chicago, Illinois 60607-7059 Barry G. Warner Department of Geography and Quaternary Sciences Institute, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1 Andrei A. Velichko Institute for Geography, Russian Academy of Sciences, Staromonetny Pereulok 29, Moscow 109017, Russia and Glen M. MacDonald Department of Geography, UCLA, Los Angeles, California 90095-1524 Received August 12, 1998 Lake-water oxygen-isotope histories for three lakes in northern Russia, derived from the cellulose oxygen-isotope stratigraphies of sediment cores, provide the basis forpreliminary reconstruction of Holocene paleohydrology in two regions along the boreal treeline. Deconvolution of shifting precipitation  18 O from secondary evap- orative isotopic enrichment is aided by knowledge of the distribu- tion of isotopes in modern precipitation, the isotopic composition of paleo-waters preserved in frozen peat deposits, as well as other supporting paleoclimatic information. These data indicate that during the early Holocene, when the boreal treeline advanced to the current arctic coastline, conditions in the lower Yenisey River region were moist compared to the present, whereas greater aridity prevailed to the east near the lower Lena River. This longitudinal moisture gradient is consistent with the suggestion that oceanic forcing (increased sea-surface temperatures in the Nordic Seas and reduced sea-ice cover) was a major contributor to the devel- opment of a more maritime climate in western Eurasia, in addition to increased summer insolation. East of the Taimyr Peninsula, large tracts of the continental shelf exposed by glacial sea-level drawdown may have suppressed maritime climatic influence in what are now coastal areas. In contrast, during the late Holocene the two regions have apparently experienced coherent shifts in effective moisture. The similarity of the records may primarily reflect reduced North Atlantic influence in the Nordic Seas and southward retreat of coastline in eastern Siberia, coupled with declining summer insolation. © 2000 University of Washington. Key Words: stable isotopes; sediment cellulose; paleoclimate; paleohydrology; treeline; Russia. INTRODUCTION The boreal forest in northern Eurasia responded dramatically to Holocene climate change. Radiocarbon dating of tree mac- rofossils found in the present-day tundra (MacDonald et al., 2000) and palynological studies on lake-sediment cores from the tundra near the lower Yenisey (Hahne and Melles, 1997) and Lena Rivers (Pisaric et al., in press) indicate that the boreal forest expanded to the arctic coast between 9000 and 7000 yr B.P. and retreated to its present location between 4000 and 3000 yr B.P., representing a northward vegetation shift of hundreds of kilometers in some sectors. Comparison with modern temperatures near the treeline suggests that mean sum- mer temperatures may have been 2.5° to 5.0°C warmer than today between 9000 and 4000 yr B.P. (MacDonald et al., 2000), results that compare well with general circulation model simulations for the Holocene (Kutzbach et al., 1993). MacDonald et al. (2000) suggest that the early Holocene 1 Also: Institut fu ¨r Hydrologie, GSF-Forschungszentrum fu ¨r Umwelt und Gesundheit, 85764 Oberschleissheim, Germany. Quaternary Research 53, 319 –329 (2000) doi:10.1006/qres.2000.2124, available online at http://www.idealibrary.com on 0033-5894/00 $35.00 Copyright © 2000 by the University of Washington. All rights of reproduction in any form reserved. 319