Holocene paleohydrology and paleoclimate at treeline, north-central Russia, inferred from oxygen isotope records in lake sediment cellulose

Lake-water oxygen-isotope histories for three lakes in northern Russia, der ived from the cellulose oxygen-isotope stratigraphies of sediment cores, pr ovide the basis for preliminary reconstruction of Holocene paleohydrology i n two regions along the boreal treeline, Deconvolution of shifting precipit ation delta(18)O from secondary evaporative isotopic enrichment is aided by knowledge of the distribution of isotopes in modern precipitation, the iso topic composition of paleo-waters preserved in frozen peat deposits, as wel l as other supporting paleoclimatic information. These data indicate that d uring the early Holocene, when the boreal treeline advanced to the current arctic coastline, conditions in the lower Yenisey River region were moist c ompared to the present, whereas greater aridity prevailed to the east near the lower Lena River. This longitudinal moisture gradient is consistent wit h the suggestion that oceanic forcing (increased sea-surface temperatures i n the Nordic Seas and reduced sea-ice cover) was a major contributor to the development 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 suppre ssed maritime climatic influence in what are now coastal areas, In contrast , during the late Holocene the two regions have apparently experienced cohe rent shifts in effective moisture. The similarity of the records may primar ily reflect reduced North Atlantic influence in the Nordic Seas and southwa rd retreat of coastline in eastern Siberia, coupled with declining summer i nsolation, (C) 2000 University of Washington.