Moisture origin and stable isotope characteristics of precipitation in southeast Siberia

Abstract

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 δ 18 O (up to −4‰) and δD (up to −40‰) values characterize summer air masses, and lighter isotope composition (−41‰ for δ 18 O 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 (r 2 = 0.83; p <.01; n = 55) for δ 18 O and +3.8‰/ C (r 2 = 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 δ 18 O 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 δ 18 O (r 2 = 0.87; p <.01; n = 55) and air temperature (r 2 = 0.99; p <.01; n = 71). However, the ECHAM5-wiso model fails to capture observed variations in d excess (r 2 = 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. K E Y W O R D Satmospheric circulation, Baikal region, d excess, ECHAM5-wiso climate model, HYSPLIT model, stable oxygen and hydrogen isotopes of precipitation

Hydrological (in)stability in Southern Siberia during the Younger Dryas and early Holocene

“…The Baunt ẟ 18 O diatom record has a range in values of 9.4‰, and if these were driven purely by changes in the lake water temperature, it indicates temperature changes through this period that appear unrealistic. This is because the Dansgaard temperature dependence relationship suggests that for every 1 • C air temperature increase the ẟ 18 O precipitation value only increases by +0.50‰ in Irkutsk (Kostrova et al, 2020). Alongside the air temperature fractionation, the diatom silica to water fractionation gradient is − 0.2‰/ • C (Dodd and Sharp, 2010;Leng and Barker, 2006), and combined, these cause a + 0.3‰ increase in ẟ 18 O diatom , for every 1 • C air temperature increase.…”

“…However, recent work indicates the region is influenced by the Atlantic westerlies, the East Asian Monsoon, and intrusions of Arctic air (Kostrova et al, 2020; Osipova and Osipov, 2019). The relative proportion of these sources varies across the year, with winter months and transitional periods (March-April-May and September-October-November) dominated by westerly precipitation (Kostrova et al, 2020;Osipova and Osipov, 2019), while during summer, inflows from the south-west and south-east increase (Osipova and Osipov, 2019). Variations in the contribution from these sources change across the Transbaikal mountains, with southern regions being more heavily influenced by southerly sources (Osipova and Osipov, 2019).…”

“…Changes in the strength of the Siberian High will also be important, with periods of increased strength reducing the overall summer precipitation levels and increasing the proportion of snowmelt entering the lake waters (Park et al, 2014;Tubi and Dayan, 2013), while during periods of weaker Siberian High, summer precipitation is proportionally more important. The varying proportion of snowmelt is also important, as the ẟ 18 O snow has much lower values (suggested ẟ 18 O snow of − 29.1‰ and − 41.4‰; data from Chizhova et al (2015) and Kostrova et al (2020) respectively), than the current summer (JJA) ẟ 18 O precipitation values, which range between ~ − 12.8‰ (Chizhova et al, 2015) and ~ − 4.0‰ (Kostrova et al, 2020) , and thus, changed proportions of these will influence the ẟ 18 O lakewater values and consequently the ẟ 18 O diatom values.…”

“…For Lake Baunt at this time, we consider that as previous values at ~10.0 ka cal BP reached +31.0‰, it is likely Early Holocene warming, linked to orbital changes, triggered an increase in glacier melt local to Baunt. As ẟ 18 O snowmelt is much lower than precipitation (Kostrova et al, 2020), this may be driving the decline to lower ẟ 18 O diatom values. A further small decline at ~9.6 + 0.11 in Baikal is not correlated to any Siberian High shifts (Fig.…”

Deuterium Excess in Precipitation Reveals Water Vapor Source in the Monsoon Margin Sites in Northwest China

“…As far as isotope techniques are concerned, knowledge has been accumulated worldwide regarding the relation between the isotopic composition and the origin of the water vapor in various regions of the world [17][18][19][20]. Since the d value in precipitation depends on meteorological conditions at the water vapor source regions, changes in d values in precipitation can be used to trace the water vapor to a certain area [21][22][23][24].…”