Climate and environmental changes of the Lategacial 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 δ¹⁸O_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 ∼13.2 cal ka BP. Most recent δ¹⁸O_diatom (+21.5‰) combined with present-day average δ¹⁸O_lake (−16.5‰) allows calculating T_lake (∼21 °C), reflecting summer conditions. Nonetheless, the δ¹⁸O_diatom variability is associated with changes in δ¹⁸O_lake rather than with T_lake. An obvious shift of ∼2‰ in the δ¹⁸O_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 δ¹⁸O_diatom during the Early Holocene suggests relatively warm and/or dry climate with associated evaporation effects. The absolute maximum in δ¹⁸O_diatom of +27.7‰ consistent with high values of diatom indices at ∼7.9–7.0 cal ka BP suggests a Mid Holocene Thermal Maximum. A continuous depletion in δ¹⁸O_diatom since ∼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 (∼0.3‰ 1000 yr⁻¹) throughout the Holocene follows decreasing solar insolation. The pattern of the Lake Emanda δ¹⁸O_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 ∼40% each, as well as ∼20% from the north.