Fluvial carbon dioxide emission from the Lena River basin during the spring flood

Greenhouse gas (GHG) emission from inland waters of permafrost-affected regions is one of the key factors of circumpolar aquatic ecosystem response to climate warming and permafrost thaw. Riverine systems of central and eastern Siberia contribute a significant part of the water and carbon (C) export to the Arctic Ocean, yet their C exchange with the atmosphere remains poorly known due to lack of in situ GHG concentration and emission estimates. Here we present the results of continuous in situ pCO2 measurements over a 2600 km transect of the Lena River main stem and lower reaches of 20 major tributaries (together representing a watershed area of 1 661 000 km2, 66 % of the Lena's basin), conducted at the peak of the spring flood. The pCO2 in the Lena (range 400–1400 µatm) and tributaries (range 400–1600 µatm) remained generally stable (within ca. 20 %) over the night–day period and across the river channels. The pCO2 in tributaries increased northward with mean annual temperature decrease and permafrost increase; this change was positively correlated with C stock in soil, the proportion of deciduous needleleaf forest, and the riparian vegetation. Based on gas transfer coefficients obtained from rivers of the Siberian permafrost zone (k=4.46 m d−1), we calculated CO2 emission for the main stem and tributaries. Typical fluxes ranged from 1 to 2 gCm-2d-1 (>99 % CO2, <1 % CH4), which is comparable with CO2 emission measured in the Kolyma, Yukon, and Mackenzie rivers and permafrost-affected rivers in western Siberia. The areal C emissions from lotic waters of the Lena watershed were quantified by taking into account the total area of permanent and seasonal water of the Lena basin (28 000 km2 ). Assuming 6 months of the year to be an open water period with no emission under ice, the annual C emission from the whole Lena basin is estimated as 8.3±2.5 Tg C yr−1, which is comparable to the DOC and dissolved inorganic carbon (DIC) lateral export to the Arctic Ocean.

Assessment of changes in air temperature and precipitation in Transbaikalia

Assessment of changes in air temperature and precipitation in Transbaikalia/ Smakhtin V.K. // Hydrometeorological Research and Forecasting, 2021, no. 2 (380), pp. 138-146. The paper analyzes long-term fluctuations in average air temperature and annual total precipitation in Transbaikalia. Between 1951 and 2020, air temperature increased by 2.3 °C according to 40 weather stations. Warming is mainly manifested in the air temperature rise in February, March and April. From 1955 to 2017, the decrease in annual total precipitation was 56 mm in the Amur basin and 39 mm in the Yenisei basin. The trends are reliable at the 5% significance level. In the Lena basin, annual total precipitation during the mentioned period increased by 7 mm, the trend is not reliable at the 5% significance level. The high-water phase has been observed since 2017. Taking into account that two previous high-water phases lasted 16‒17 years, it may be supposed that a risk of precipitation above the normal will be kept in the next 13–14 years. Keywords: climate change, air temperature, precipitation, phases of water content, trendsRef. 81.

Some aspects of the navigation period extension in the North-West Basin of inland waterways of the Russian Federation

The Russian Federation has a developed system of inland waterways (IWW) [1]. This system consists of 15 basins. Winter conditions are very harsh in some basins. Such basins, for example, include the Lena Basin. But in some basins, even in winter, conditions that block navigation do not form. These basins include the Volga-Baltic. However, during the extension of the navigation period in such basins, it should be borne in mind that the navigation safety system will have to be upgraded. This paper discusses some aspects, the introduction of which forms the prerequisites for extension of the navigation period on the waterways of the North-Western region of the Russian Federation. In addition, specific recommendations are provided for the implementation of the necessary automated systems to ensure a sufficient level of navigation in winter conditions on the IWW. These recommendations were obtained within the framework of the international project INFUTURE.

Sculpin Cottus cf. poecilopus Heckel, 1837 in Baikal Lake Basin: First Findings

For the first time for the Baikal Lake basin, evidence of the existence of populations of sculpin Cottus cf. poecilopus Heckel (alpine bullhead) characteristic of the adjacent Lena River basin in large northern Baikal tributaries, the Verkhnaya (Upper) Angara and the Kichera is provided. In June 2009 during the study of the lower reaches of the Kholodnaya River (Kichera-Baikal system), 8 individuals of sculpin aged from 3 to 5 years and in August 2009 5 more specimens aged from 4 to 6 were caught. All fish were fertile with the gonads in maturity stage III. In August 2010 33 individuals aged from 4 to 6 were collected in the main channel of the Upper Angara near Novy Uoyan settl.. At about the same time C.poecilopus was registered in stomachs of Arctic charr from Lake Amut (Churo-Upper Angara-Baikal system) near the divide with the Pravaya (Right) Mama (Mama-Vitim-Lena system). In August 2010 17 specimens aged from 1 to 4 were caught in the Upper Angara near the mouth of its large left tributary the Yanchui River. Sculpins from the rivers Kholodnaya, Upper Angara and Yanchui have higher growth rate as compared to the ones from mountain lakes of the upper Lena basin. About 90 % of males and females matured at the age of 3 years. Absolute fecundity of two females from the Upper Angara River was 149 and 556 (with a mean of 352,5) eggs and of two females from the Kholodnaya River, 223 and 305 (with a mean of 264) eggs. This exceeds the fecundity of sculpins from mountain lakes in the Lena part of Baikal rift zone, which averages less than 150 eggs. Sculpins spawn in the Kholodnaya River in the 1st half of June. The diet of C. cf. poecilopus all over the Baikal basin as well as in adjacent sites in the Lena basin was basically composed of larvae of amphibious insects (trichopterans, ephemeropterans, chironomids and plecopterans). The discovery of the third species from the Lena basin in the Baikal basin following the findings of Arctic charr Salvelinus alpinus and grayling Thymallus baicalolenensis evidences the absence of differences in the structure of ichthyofaunas of the upper parts of both neighboring basins. Sculpins permeate along the streams to mountain lakes more easily than other species and colonize the most elevated ones in lake cascades within the northern part of Baikal rift zone. Their dispersal across the divide could proceed in two ways: via headwater captures or via flattened passes between converging upper reaches of adjacent streams.