Climate And Environmental Changes Of The Lateglacial Transition And Holocene In Northeastern Siberia: Evidence From Diatom Oxygen Isotopes And Assemblage Composition At Lake Emanda

A new dataset from Lake Emanda provides insights into climate and environmental dynamics in an extreme continental setting in northeastern Siberia. The delta O-18(diatom) record is supported by diatom assemblage analysis, modern isotope hydrology and atmospheric circulation patterns. The data reveal a relatively cold oligotrophic freshwater lake system persisting for the last similar to 13.2 cal ka BP. Most recent delta O-18(diatom) (+21.5 parts per thousand) combined with present-day average delta O-18(lake) (-16.5 parts per thousand) allows calculating T-lake (similar to 21 degrees C), reflecting summer conditions. Nonetheless, the delta O-18(diatom) variability is associated with changes in delta O-18(lake) rather than with T-lake. An obvious shift of similar to 2 parts per thousand in the delta O-18(diatom) record at 11.7-11.5 cal ka BP accompanied by significant changes in diatom assemblages reflects the onset of the Holocene. Relatively high delta O-18(diatom) during the Early Holocene suggests relatively warm and/or dry climate with associated evaporation effects. The absolute maximum in delta O-18(diatom) of +27.7 parts per thousand consistent with high values of diatom indices at similar to 7.9-7.0 cal ka BP suggests a Mid Holocene Thermal Maximum. A continuous depletion in delta O-18(diatom) since similar to 5.0 cal ka BP is interpreted as Middle to Late Holocene cooling reaching the absolute minimum at 0.4 cal ka BP (i.e. the Little Ice Age). An overall cooling trend (similar to 0.3 parts per thousand 1000 yr(-1)) throughout the Holocene follows decreasing solar insolation. The pattern of the Lake Emanda delta O-18(diatom) record is similar to that obtained from Lake El'gygytgyn suggesting a common "eastern" regional signal in both records, despite their hydrological differences. Presently, atmospheric moisture reaches the study region from the west and east with similar to 40% each, as well as similar to 20% from the north. (C) 2021 The Author(s). Published by Elsevier Ltd.