Examinando por Autor "Kostrova, S."

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    Diatom oxygen isotope records of Northern Eurasia as indicators of environmental, hydrological and climate changes in the regions
    (Limnological Institute SB RAS, 2022-09-08) Kostrova, S.; Bailey, H.; Biskaborn, B.; Chapligin, B.; Dvornikov, Y.; Ekaykin, A.; Fernandoy, F.; Kozachek, A.; Kuhn, G.; Ludikova, A.; Meister, P.; Nazarova, L.; Pestryakova, L.; Shibaev, Y.; Syrykh, L.; Meyer, H.
    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 (δ18Odiatom) preserved in sediment cores from Ladoga, Bolshoye Shchuchye and Emanda lakes. Interpretation of the δ18Odiatom data is supported by a comprehensive study of modern isotope hydrology and analysis of local and regional proxies. The Northern Eurasia δ18Odiatom records are characterized by pronounced short term variations (1.5–5‰), 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 δ18Odiatom 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. © Author(s) 2022.
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    Moisture origin and stable isotope characteristics of precipitation in southeast Siberia
    (John Wiley and Sons Ltd, 2020) Kostrova, S.; Meyer, H.; Fernandoy, F.; Werner, M.; Tarasov, P.
    The paper presents oxygen and hydrogen isotopes of 284 precipitation event samples systematically collected in Irkutsk, in the Baikal region (southeast Siberia), between June 2011 and April 2017. This is the first high-resolution dataset of stable isotopes of precipitation from this poorly studied region of continental Asia, which has a high potential for isotope-based palaeoclimate research. The dataset revealed distinct seasonal variations: relatively high δ18O (up to −4‰) and δD (up to −40‰) values characterize summer air masses, and lighter isotope composition (−41‰ for δ18O and −322‰ for δD) is characteristic of winter precipitation. Our results show that air temperature mainly affects the isotope composition of precipitation, and no significant correlations were obtained for precipitation amount and relative humidity. A new temperature dependence was established for weighted mean monthly precipitation: +0.50‰/°C (r2 = 0.83; p <.01; n = 55) for δ18O and +3.8‰/°C (r2 = 0.83, p < 0.01; n = 55) for δD. Secondary fractionation processes (e.g., contribution of recycled moisture) were identified mainly in summer from low d excess. Backward trajectories assessed with the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) model indicate that precipitation with the lowest mean δ18O and δD values reaches Irkutsk in winter related to moisture transport from the Arctic. Precipitation originating from the west/southwest with the heaviest mean isotope composition reaches Irkutsk in summer, thus representing moisture transport across Eurasia. Generally, moisture transport from the west, that is, the Atlantic Ocean predominates throughout the year. A comparison of our new isotope dataset with simulation results using the European Centre/Hamburg version 5 (ECHAM5)-wiso climate model reveals a good agreement of variations in δ18O (r2 = 0.87; p <.01; n = 55) and air temperature (r2 = 0.99; p <.01; n = 71). However, the ECHAM5-wiso model fails to capture observed variations in d excess (r2 = 0.14; p < 0.01; n = 55). This disagreement can be partly explained by a model deficit of capturing regional hydrological processes associated with secondary moisture supply in summer.