A climatological interpretation of precipitation-based δ¹⁸O across Siberia and Central Asia

Abstract. Siberia and Central Asia are located at mid- to high latitudes and encompass a large landlocked area of the Eurasian continent containing vast tracts of permafrost (seasonal permafrost and permafrost), which is extremely sensitive to global climate change. However, previous research has scarcely investigated the changes in the paleoclimate in this region. Similarly, the temporal and spatial distributions of the stable isotopic composition (δ¹⁸O_P) of precipitation and its corresponding influencing factors remain largely unknown. Therefore, we used data from 15 Global Network of Isotopes in Precipitation (GNIP) stations to investigate the relationships between δ¹⁸O_P and the local temperature and precipitation considering changes in atmospheric circulation. Analyses conducted on the monthly, seasonal and annual timescales led to three main conclusions. (1) At the monthly timescale, the variations in δ¹⁸O_P exhibited a significant positive correlation with the monthly mean temperature (p < 0.01). The δ¹⁸O_P excursion was positive in summer as the temperature increased and negative in winter as the temperature decreased. Note that the δ¹⁸O_P values were also affected by the monthly precipitation, Eurasian zonal circulation index (EZCI), and water vapor source (e.g., polar air masses and local evaporative water vapor). (2) At the annual scale, the weighted average value of the precipitation-based δ¹⁸O (δ¹⁸O_W) exhibited a temperature effect over 60° N–70° N. However, δ¹⁸O_W may have been dominated by multiple factors from 40° N to 60° N (e.g., the North Atlantic Oscillation (NAO) and water vapor source changes). (3) At the annual timescale, the variability of the path of the westerly caused by changes in the NAO explained the variations in both δ¹⁸O_P and δ¹⁸O_W. Based on the limited observational data in this region, we found that δ¹⁸O_P is correlated with the local temperature at the monthly and seasonal timescales. However, at the annual timescale, in addition to the temperature effect, δ¹⁸O_P reflects the variability of the water vapor source that is dominated by the EZCI and NAO. Therefore, it is possible to reconstruct the histories of past atmospheric circulations and water vapor sources in this region via geologic δ¹⁸O proxies, e.g., speleothems records.