Diatom oxygen isotope records of Northern Eurasia as indicators of environmental, hydrological and climate changes in the regions

The environmental, hydrological and climate dynamics were assessed in Northern Eurasia during the Holocene. The reconstructions are based on oxygen isotope composition of lacustrine diatom silica (δ¹⁸O_diatom) preserved in sediment cores from Ladoga, Bolshoye Shchuchye and Emanda lakes. Interpretation of the δ¹⁸O_diatom data is supported by a comprehensive study of modern isotope hydrology and analysis of local and regional proxies. The Northern Eurasia δ¹⁸O_diatom records are characterized by pronounced short term variations (1.5-5%o), pointing to the unstable climatic and hydrological conditions in the study regions. All records have clearly demonstrated a gradual depletion over the Holocene in their δ¹⁸O_diatom values by ~3-4%, which follows the trend of decreasing summer insolation, as well as the temperature history of the Northern Hemisphere (NH), indicating a positive response of diatom oxygen isotope signal to large-scale climate changes.