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Based on simulations with an ensemble of CMIP6 (Coupled Models Intercomparison Project, phase 6) climate models using Bayesian averaging, an analysis of changes in the runoff of a number of Russian rivers—the Volga, Ob, Yenisei, Lena, Amur, and Selenga—has been carried out this century. Bayesian weights take into account the skill of runoff reproduction by models (long-term average runoff, linear runoff trend over a time interval with available runoff observations, and interannual and interdecadal variability). The skill of reproduction of runoff characteristics by individual CMIP6 ensemble models varies most widely for long-term average runoff; runoff trend; and, to a lesser extent, interannual variability. In the 21st century, the ensemble average runoff increases for most of the analyzed rivers, with the exception of the Volga. This increase is more pronounced in scenarios with large anthropogenic impacts. It is especially significant for the SSP5-8.5 scenario (Shared Socioeconomic Pathways, 14 5-8.5), in which the trend of increase in runoff in 2015–2100 relative to its modern long-term average value is (10 ± 4)% for the Ob, (16 ± 3)% for the Yenisei, (39 ± 7)% for the Lena, (36 ± 7)% for the Amur, and (18 ± 6)% for the Selenga. The main reason for changes in ensemble average runoff in the 21st century in models under all SSP scenarios is the changes in precipitation. Accounting for differences in model skill when reproducing river runoff on average for 2015–2100 reduces intermodel deviations relative to the corresponding values when uniformly weighting the model calculation results by 6–26%, depending on the SSP scenario and river catchment. [ABSTRACT FROM AUTHOR]

We present the first magnetotelluric sounding (MTS) data acquired in the southern part of the Lena River delta which is a junction zone of the Siberian Craton and the Verkhoyansk fold-and-thrust belt, in the transition zone from the Eurasian Continent to the shelf of the Laptev Sea. The MTS data were used to construct a vertical section of the bulk electrical resistivity (ER) structure of the Earth's crust down to a depth of 8 km. The upper high-resistivity layer (320–1000 Ohm m) corresponds to the permafrost rocks ranging in thickness from 1 km to 400 m under the channels of the Lena River. The underlying deformed Mesoproterozoic–Lower Triassic rocks can vary in composition, but they are poorly differentiated in ER values (110–240 Ohm m). We detected three low-resistivity anomalies (10–60 Ohm m) related to the fluid-saturated core and damage zones of active faults. A deep-lying high-resistivity anomaly (320–350 Ohm m) identified at the northeastern part of the section can correspond to the Lower Proterozoic or Archean metamorphic rocks. [ABSTRACT FROM AUTHOR]

Currently, inland water transport is the main mode of transport in the Republic of Sakha (Yakutia). The Lena remains the main river connecting Yakutia with the federal transport infrastructure. However, the state of the Republic’s transport infrastructure does not meet the needs of its economy The infrastructure limits the effective realization of the industrial and resource potential and use of the geographical position of the Republic of Sakha. Therefore, to provide an insightful analysis of the factors affecting the logistics of the Lena River, we conducted a detailed analysis of the current problems of the inland waters of the Republic. This article analyzes the logistics of the Lena River and presents an assessment of the problems hindering the process of modernizing the inland water transport of the Republic of Sakha. Analyzing the factors for revitalizing the Lena River logistics through the Interpretative Structural Modeling method revealed the region’s main water transport logistics problems. Through the literature review, 12 key factors affecting the logistics of the Lena River were identified, and interrelationships among them were represented. The results illustrate that inland water transport of the Republic requires the development of transport infrastructure and financial support from the state to implement republican targeted programs. Therefore, this study is important in both academic and practical aspects.

The results of morphological and genetic analysis of populations/forms/species of the pidschian-like whitefishes from the middle and lower streams of the Lena River and adjacent rivers are presented. There are good grounds to believe that despite considerable heterogeneity of whitefishes in Siberia, a small number of stable forms/species live in the waterbodies of the Siberian Arctic. These are the East Siberian whitefish (C. lavaretus pidschian n. brachymystax), glacial—plain whitefish (C. lavaretus pidschian n. glacialis) and Yukagir whitefish (C. lavaretus pidschian n. jucagiricus), as well as their hybrid populations. The glacial—plain whitefish and its derivatives differ from the East Siberian whitefish in plastic traits but they are identical in meristic ones. Molecular genetic studies showed that, in most cases, glacial—plain whitefish formed vast loosely connected haplotype networks, which corresponded to the long-term population existence in favorable conditions. Haplotypes of the East Siberian whitefish are closely related to the haplotypes of whitefish forms/species from the waterbodies of Southern Siberia, characterized by radial structure of median-joining network. Such network structure indicates a recent decline in the East Siberian whitefish numbers with subsequent expansion, which is directly associated with the Quaternary glaciation events. [ABSTRACT FROM AUTHOR]

The species composition of water fleas (Crustacea: Cladocera) in the water bodies of the left bank of the Lena River near the city of Yakutsk and its vicinities has been studied. Local faunistic associations ty-pical of the region have been identified using a statistical approach based on the binomial distribution function. As a result, 68 taxa have been identified and 8 very distinct groups of taxa constituting the cores of local faunistic associations of the branchiopod crustaceans in different water bodies and/or various biotopes within a single water body have been separated. We have demonstrated that the water bodies of the Lena River valley and the watershed differ both in species composition and in associations of the Cladocera. At least one species association of Cladocera is confined to ponds under a visible anthropogenic load. Thus, not only species that are typical for urban water bodies, but also local faunistic associations whose presence in the city indicates a significant anthropogenic pressure, have been identified. Moreover, the identified clusters can be interpreted in terms of our knowledge on the individual species preferences for water bodies of different types and different ecological zones of a certain water body. [ABSTRACT FROM AUTHOR]

The hydrological models ECOMAG and HBV were used to calculate the characteristics of river flow and snow Water Equivalent in the Lena River basin. The input data included the meteorological observations and the results of calculations with global climate models with the implementation of scenarios of natural climate conditions, taking into account the anthropogenic effect on climate. The calculations were made for a historical period (1970–1999) and up to the end of the XXI century. Hydrological models for several hydrometric gages in the Lena basin were calibrated and verified. The simulation of the annual and seasonal runoff using the climate model data was evaluated by comparison with observation data. According to the results using numerical experiments over the historical period, the increase in the Lena runoff is mostly due to natural climate variations. Conversely, in the XXI century, the anthropogenic climate changes determine the specific features of the regime of river runoff and snow cover. The warming caused by an increase in greenhouse gas concentrations in the atmosphere leads to an increase in snow water equivalent and transformation of the hydrological regime in the area, in particular, to an earlier beginning of active snow melting (up to two weeks) and higher maximal discharges during spring flood. At the same time, the volume of runoff decreases in the summer and increases in the autumn and winter. [ABSTRACT FROM AUTHOR]

Currently, inland water transport is the main mode of transport in the Republic of Sakha (Yakutia). The Lena remains the main river connecting Yakutia with the federal transport infrastructure. However, the state of the Republic's transport infrastructure does not meet the needs of its economy The infrastructure limits the effective realization of the industrial and resource potential and use of the geographical position of the Republic of Sakha. Therefore, to provide an insightful analysis of the factors affecting the logistics of the Lena River, we conducted a detailed analysis of the current problems of the inland waters of the Republic. This article analyzes the logistics of the Lena River and presents an assessment of the problems hindering the process of modernizing the inland water transport of the Republic of Sakha. Analyzing the factors for revitalizing the Lena River logistics through the Interpretative Structural Modeling method revealed the region's main water transport logistics problems. Through the literature review, 12 key factors affecting the logistics of the Lena River were identified, and interrelationships among them were represented. The results illustrate that inland water transport of the Republic requires the development of transport infrastructure and financial support from the state to implement republican targeted programs. Therefore, this study is important in both academic and practical aspects. [ABSTRACT FROM AUTHOR]

The age composition and fecundity of taimen (Hucho taimen) spawners at spawning grounds located in left tributaries of the Lena River (Muna and Motorchuna rivers) are analyzed. Spawning season takes place in May–June. The age of spawners varies from 8 to 17 years. The absolute fecundity of taimens from Muna and Motorchuna rivers is more than in those from the western part of species range and smaller than in populations from eastern part of range. Taimen individuals from the river under study are part of a large population of the species in the Lena River. They forage and overwinter in the Lena River and enter its tributaries, including the Muna and Motorchuna rivers, only for reproduction. This is also typical for taimens from basins of other large rivers (the Kama, Yenisei, and Amur). The stock abundance of taimen is not large. Spawners at spawning sets needs special protection measures. [ABSTRACT FROM AUTHOR]

The discharge of rivers and the subsequent dispersion of their plumes play a pivotal role in the biogeochemical cycling of the Arctic Ocean. Based on the data collected during annual transects conducted in the autumn period (September-October) from 2015-2020, this study explores the effect of River Lena plume dispersion on the seasonal and interannual changes in the hydrophysical and biogeochemical structure of the southeastern Laptev Sea. The temperature-salinity relationship (T-S), Redfield ratio and multiparameter cluster analysis were used to investigate variations in the water mass structure along the transect. The results revealed that the plume’s interannual and seasonal spreading patterns play a crucial role in regulating the local physical, biogeochemical, and biological processes in the southern Laptev Sea. During September-October, the hydrochemical water mass structure along the transects shifted from highly stratified to unstratified as the plume’s mixing intensity increased. Anomalous hydrochemical distributions were observed due to coastal upwelling, which was primarily characterized by high total alkalinity and nitrate levels, and low organic phosphorus, nitrite, and ammonia levels in the seawater. Wind and cold weather conditions drive deep vertical mixing of seawater, causing the resuspension of bottom sediment and the subsequent enrichment of bottom water by nutrients. Multi-parameter cluster analysis is used to describe the details of water mass structures in the highly dynamic southern Laptev Sea, with water mass structures typically undergoing significant changes within two weeks between September and October. The migration and transformation of water masses throughout the seasons are influenced by the volume of river discharge, fall-winter cooling, and atmospheric circulation patterns. Furthermore, the general atmospheric circulation is confirmed to be the primary cause of the interannual variation in the spread of the Lena River plume over the southeast Laptev Sea.

In the past decades the Arctic has experienced stronger temperature increases than any other region globally. Shifts in hydrological regimes and accelerated permafrost thawing have been observed and are likely to increase mobilization of organic carbon and its transport through rivers into the Arctic Ocean. In order to better quantify changes to the carbon cycle, Arctic rivers such as the Lena River in Siberia need to be monitored closely. Since 2018, a sampling program provides frequent in situ observations of dissolved organic carbon (DOC) and colored dissolved organic matter (CDOM) of the Lena River. Here, we utilize this ground truth dataset and aim to test the potential of frequent satellite observations to spatially and temporally complement and expand these observations. We explored all available overpasses (~3250) of the Ocean and Land Colour Instrument (OLCI) on Sentinel-3 within the ice-free periods (May – October) for four years (2018 to 2021) to develop a new retrieval scheme to derive concentrations of DOC. OLCI observations with a spatial resolution of ~300 m were corrected for atmospheric effects using the Polymer algorithm. The results of this study show that using this new retrieval, remotely sensed DOC concentrations agree well with in situ DOC concentrations (MAPD=10.89%, RMSE=1.55 mg L−1, r²=0.92, n=489). The high revisit frequency and wide swath of OLCI allow it to capture the entire range of DOC concentrations and their seasonal variability. Estimated satellite-derived DOC export fluxes integrated over the ice-free periods of 2018 to 2021 show a high interannual variability and agree well with flux estimates from in situ data (RMSD=0.186 Tg C, MAPD=4.05%). In addition, 10-day OLCI composites covering the entire Lena River catchment revealed increasing DOC concentration and local sources of DOC along the Lena from south to north. We conclude that moderate resolution satellite imagers such as OLCI are very capable of observing DOC concentrations in large/wide rivers such as the Lena River despite the relatively coarse spatial resolution. The global coverage of remote sensing offers the expansion to more rivers in order to improve our understanding of the land-ocean carbon fluxes in a changing climate.

Correlations between the amount of precipitation in the Lena and Yana river basins in winter and the ice coverage of the Laptev and East Siberian seas near the New Siberian Islands in the spring-summer period are studied based on the GLORYS12v.1 and ERA5 global reanalyses and archival meteorological data. A statistically significant correlation (with a confidence level of at least 0.95) was established in the certain parts of the study area. The Yana basin winter precipitation was found to have the highest correlation with the ice coverage in May. The correlation between the Lena basin precipitation and the ice coverage in July is lower, but also significant. During the other months, no significant correlations were revealed. The established facts may be of practical use for long-range forecasting of ice conditions near the New Siberian Islands at the beginning of the summer navigation along the Northern Sea Route. [ABSTRACT FROM AUTHOR]

Arctic warming and permafrost thaw visibly expose changes in the landscape of the Lena River delta, the largest Arctic delta. Determining the past and modern river regime of thick deltaic deposits shaping the Lena River mouth in north‐eastern Siberia is critical for understanding the history of delta formation and carbon sequestration. Using a 65 m long sediment core from the delta apex a set of sedimentological techniques is applied to aid in reconstructing the Lena River history. The analysis includes: (i) grain‐size measurements and the determination of the bedload composition; (ii) X‐ray fluorescence, X‐ray diffractometry, and magnetic susceptibility measurements and heavy mineral analysis for tracking mineral change; (iii) pH, electrical conductivity, ionic concentrations, and the δ18O and δD stable isotope composition from ground ice for reconstructing permafrost formation. In addition; (iv) total and dissolved organic carbon is assessed. Chronology is based on; (vi) radiocarbon dating of organic material (accelerator mass spectrometry and conventional) and is complemented by two infrared – optically stimulated luminescence dates. The record stretches back approximately to Marine Isotope Stage 7. It holds periods from traction, over saltation, to suspension load sedimentation. Minerogenic signals do not indicate provenance change over time. They rather reflect the change from high energy to a lower energy regime after Last Glacial Maximum time parallel to the fining‐up grain‐size trend. A prominent minimum in the ground ice stable isotope record at early Holocene highlights that a river arm migration and an associated refreeze of the underlying river talik has altered the isotopic composition at that time. Fluvial re‐routing might be explained by internal dynamics in the Lena River lowland or due to a tectonic movement, since the study area is placed in a zone of seismic activity. At the southern Laptev Sea margin, onshore continental compressional patterns are bordering offshore extensional normal faults. [ABSTRACT FROM AUTHOR]

The distribution of fresh water in the East Siberian Sea (ESS) and Laptev Sea (LS) in the period of the least ice coverage (August–October) has been analyzed using satellite data on sea level and CTD data from ship observations. It is shown that there is a good agreement between the salinity/density distribution in the surface water layer and the sea level in the study area. An increase (decrease) in the runoff of the Lena River during the summer flood leads to an increase (decrease) in the sea level in the eastern part of the LS and in the western and southwestern parts of the ESS in September and October (r = 0.52–0.59 in 1993–2019). The intensification of the western winds is accompanied by a decrease in salinity and a rise in sea level in the coastal areas of the LS and ESS. Eastern winds cause a decrease in sea level in the southern regions of the LS and ESS and the flow of waters with low salinity from the coastal to the open part of the sea. Western/eastern winds are accompanied by eastern/western directed geostrophic currents in the region of the Sannikov Strait and in the southwestern part of the ESS. [ABSTRACT FROM AUTHOR]

Permafrost degradation has led to increased riverine ion concentrations and export to the sea. This study uses major ion data collected in summer in 2012 and 2013 and during spring flood in 2015 to investigate the spatio-temporal variability in chemical weathering patterns and the associated CO 2 consumptions in one of the major Arctic Rivers – the Lena River and its tributaries. The catchment shows strong spatial variations in major ion concentrations in the main river and tributaries. The weathering flux represented by TIS (total inorganic solids) is calculated to be 112 Tg/yr, which is almost double that calculated in an earlier study 20 years ago for the same region. The CO 2 consumption is estimated to be 4.9 Tg C/yr, which is approximately equally shared between weathering of carbonates and silicates, despite two thirds of TIS derived from carbonates and the rest of TIS by silicates and evaporites. Our results suggest an enhanced role for silicate weathering in elemental export and CO 2 drawdown due to the ongoing transition from a near surface-dominated system towards a deep groundwater dominated system caused by permafrost degradation in the Arctic region under a warmer climate. Such an enhanced weathering pattern is also expected in other Arctic rivers; hence, a re-evaluation of the weathering budgets is clearly needed. Our findings improve our understanding of the response of the weathering regime in large Arctic river catchments to ongoing climate-driven permafrost loss, which also sheds lights into the role of land-sea element fluxes in sustaining primary production and carbon cycling on the Arctic shelf seas. [ABSTRACT FROM AUTHOR]

The results from morphogenetic analysis of the whitefish populations from the middle stream of the Lena River and sympatric whitefish forms/species from the Baunt lake system are presented. The data showed that the lakes were inhabited by up to eight whitefish forms/species with relatively high degree of differentiation. The Dorong, Baunt, and Bolshye Kapylyushi lakes were found to be inhabited by sympatric whitefishes, similar in the number of gill rakers, but different in the perforated lateral line scale numbers. In addition, in Lake Baunt, endemic cisco-like densely rakered whitefish was found. Analysis of the mtDNA ND1 gene variation in different forms, including the whitefish populations from the middle stream of the Lena River, showed that the whitefish haplotypes from the Baunt lake system were strongly mixed and were based on several well-defined phylogenetic lineages. The cisco-like whitefish is of more ancient origin than other species of the pidschian-like whitefishes of the genus Coregonus. [ABSTRACT FROM AUTHOR]

This paper studies the possibility of using the WaTEM/SEDEM model to assess sediment yield from the catchment area within the Lena River catchment. The study was carried out based on a comparison of predicted data and measured data of the suspended sediment yield at the gauging stations of the state monitoring network of Russia. The study was performed within two areas, with plain and mountainous relief. The first site is located within the catchment area of the river Chara with an area of 4150 km2. The second site rests on the catchment area of the Lena River between the Tabaginskiy and Kangalassky capes near Yakutsk city. The catchment area of this site is 15,740 km2. The values of sediment yield from the "Yakutsk" catchment area are in much better agreement with the values of the measured sediment yield values than in the "Chara" catchment area. The predicted sediment yield from the study area remained almost unchanged from the period 1986–2019 and amounted to 3.5 t/km2, while the suspended sediment yield in the Lena at the Tabaga gauging station slightly increased from 7 to 9.45 t/km2 per year. [ABSTRACT FROM AUTHOR]

The article is devoted to the cultural heritage sites of memorial importance, which are included in the complex of the Cultural and Educational Center named after St. Innokenty Veniaminov opened in 2017 in his homeland, the Verkholensk village of Anga: the hut where he spent his childhood, and the foundations of the lost Church of the Prophet Elijah, in which he helped his uncle deacon in his divine service.

Central Yakutia is a large region in northeastern Siberia characterized by extensive permafrost, large river valleys, mountain glaciers, and large massifs of aeolian sands; the geological history of the region is complex and, at present, poorly constrained. In recent years, it has been shown that aeolian sands cover up to 60% of large parts of Central Yakutia. This paper presents the results of luminescence dating of aeolian sedimentation at the Diring Yuriakh Palaeolithic site located in the middle reaches of the Lena River. Field studies identified several thick units of aeolian sand, which cover an old deflation surface with Late (Duktai culture) and Early Palaeolithic (Diring culture) artefacts. The reliability of the OSL chronology was assessed by comparison of ages based on the optically stimulated luminescence from quartz and the infra-red stimulated luminescence from potassium-rich feldspars; these age pairs are in good agreement, implying that at least the quartz grains were sufficiently bleached before sedimentation. We obtained OSL ages that reflect three periods of accumulation between the LGM and the Holocene: ∼21 ka, 15-14 ka, and 12.5–10 ka. These periods of accumulation broadly coincide with global cooling episodes during the Last Glacial Maximum, the Older Dryas, and the Younger Dryas, with some extension into subsequent warmer intervals, whereas the intervening intervals without preserved sediments are taken to reflect dune stability during warmer periods. The sand on the terraces, sourced from alluvial bars in the river channel, was blown up the valley slope during cold and dry periods when the vegetation cover was sparse. When the climate warmed, the vegetation took some time to spread, and so the accumulation of aeolian sand on the high terraces continued into the warm periods. We also infer periods of deflation (wind erosion) that occurred before 21 ka and between 20 and 15 ka, presumably due to increased aeolian activity and localized remobilization of sediment. The new OSL chronology shows that the younger artefacts located at the cape of Diring Yuriakh, belonging to the Late Palaeolithic Duktai culture, are older than 15 ka. The new ages also show that the post-LGM aeolian sand sequences at Diring Yuriakh are correlated with the regionally developed subaerial Dolkuma Formation. [ABSTRACT FROM AUTHOR]

The possibility of using river seismic data for oil and gas exploration to study the deep structure of the Earth's crust is shown. This method uses water seismic source points and bank-mounted autonomous seismic recorders installed for continuous seismic recording. About 2700 km of seismic profiles were completed by the CDP-2D method along the rivers of Eastern Siberia (Lena, Nizhnyaya Tunguska, and Vitim). The structure of the upper part of the Earth's crust (up to several kilometers) has been studied, while its deep structure remains unknown. It is shown that the materials of seismic river surveys carried out along a 60-km section of the profile in the lower reaches of the Lena River, using the method developed by the Geophysical Survey, Russian Academy of Sciences, contain data allowing us to construct cross sections throughout the thickness of the Earth's crust up to the Moho boundary. Low-amplitude fluctuations of reflected waves from deep boundaries are distinguished due to the wide dynamic range of the devices used and the multiple summation, which is significantly higher than in the case of the traditional seismic surveys. The high multiplicity is achieved by reducing the distance between blast points, increasing the sounding bases and the binning area. [ABSTRACT FROM AUTHOR]

Recent evidence has shown that Arctic regions have warmed about twice as much as elsewhere on the planet over the last few decades, and that high‐latitude permafrost–periglacial processes and hydrological systems are notably responsive to rising temperatures. The aim of this paper is to report on the thermal regime of islands located along the Lena River floodplain, upstream of the city of Yakutsk (eastern Siberia). Four islands were monitored using waterproof dataloggers and continuous monitoring of frozen soil in contact with ice breakup of the Lena River. For each of these islands, we measured: (a) ground surface temperature, air and frozen soil temperatures at different depths; and (b) submersion duration during the flood. Our results show that within a zone of thick and continuous permafrost, the Lena floodplain is notably heterogeneous, with a combination of permanently and seasonally frozen islands. The ice breakups seem to have a negligible impact on the ground thermal regime. Our study confirms that relatively young (<30 years old) islands, composed of fine sand material, appear less prone to permafrost formation compared to older islands with ice‐rich silty material. [ABSTRACT FROM AUTHOR]

The first description/overview of the freshwater copepod fauna of the order Harpacticoida from the Lena River delta is presented. Various habitats and regions were studied. As a result, we identified 18 species belonging to two families: Canthocamptidae and Harpacticidae. Eight of the identified species are new to the study area; five species belonging to the genera Bryocamptus, Canthocamptus, Moraria, and Maraenobiotus, presumably represent new species for science. We provide brief ecological descriptions of the species identified in the Lena River delta and analyze their differences from the typical populations. The harpacticoid fauna of the Lena delta consists of three main components including Palaearctic species, Holarctic species, and species with "Beringian" distribution patterns. We provide a morphological description of Bryocamptus umiatensis Wilson 1958. This species is quite similar to Bryocamptus jejuensis Lee and Chang 2016, recently described from Korea. The main character distinguishing these species is the ornamentation of the anal operculum. This character in our region reveals considerable interpopulation variations. We also provide an identification key to the freshwater Canthocamptidae of the Lena delta. [ABSTRACT FROM AUTHOR]

Basing on his study of archival and literature materials, as well as his field observations and photofixation, the author explores architecture of Olyokminsk, one of the first historic towns in Siberia. He analyzes the wooden architecture of the town, stone structures, decoration of residential buildings, window surrounds, as well as the planning structure of Olyokminsk. The architecture of the lost part of the city, skoptsy’s settlement Spassky, is analyzed too.

This work is focused on the structure and inter-annual variability of the freshened surface layer (FSL) in the Laptev and East-Siberian seas during ice-free periods. This layer is formed mainly by deltaic rivers among which the Lena River contributes about two thirds of the inflowing freshwater volume. Based on in situ measurements, we show that the area of this FSL during certain years is much greater than the area of FSL in the neighboring Kara Sea, while the total annual freshwater discharge to the Laptev and East-Siberian seas is 1.5 times less than to the Kara Sea (mainly from the estuaries of the Ob and Yenisei rivers). This feature is caused by differences in morphology of the estuaries and deltas. Shallow and narrow channels of the Lena Delta are limitedly affected by sea water. As a result, undiluted Lena discharge inflows to sea from multiple channels and forms relatively shallow plume, as compared to the Ob-Yenisei plume, which mixes with subjacent saline sea water in deep and wide estuaries. Due to small vertical extents of FSL in the Laptev and East-Siberian seas, wind conditions strongly affect its spreading and determine its significant inter-annual variability, as compared to relatively stable FSL in the Kara Sea. During years with prevailing western and northern winds, FSL is localized in the southern parts of the Laptev and East-Siberian seas due to southward Ekman transport, meridional extent (

This work is focused on structure and seasonal variability of the most freshened part of the Lena plume in the south-eastern part of the Laptev Sea, namely, at sea area adjacent to the eastern part of the Lena Delta and in the Buor-Khaya Bay. Based on in situ hydrological data, it is shown that accumulation of the freshwater discharge of the Lena River occurs in the Buor-Khaya Bay during the summer period. In autumn reduced salinity in this semi-isolated and shallow gulf remains significantly longer time than in the area adjacent to the eastern part of the Lena Delta that is not typical for large river plumes. As a result, the Buor-Khaya Bay plays a role of a reservoir of freshwater discharge during long autumn-winter period. Moreover, this gulf is a secondary source of freshened and warm water in the south-eastern part of the Laptev Sea which volume is similar to the discharge volume of the Lena River during the autumn-winter drought. [ABSTRACT FROM AUTHOR]

This paper studies the possibility of using the WaTEM/SEDEM model to assess sediment yield from the catchment area within the Lena River catchment. The study was carried out based on a comparison of predicted data and measured data of the suspended sediment yield at the gauging stations of the state monitoring network of Russia. The study was performed within two areas, with plain and mountainous relief. The first site is located within the catchment area of the river Chara with an area of 4150 km2. The second site rests on the catchment area of the Lena River between the Tabaginskiy and Kangalassky capes near Yakutsk city. The catchment area of this site is 15,740 km2. The values of sediment yield from the “Yakutsk” catchment area are in much better agreement with the values of the measured sediment yield values than in the “Chara” catchment area. The predicted sediment yield from the study area remained almost unchanged from the period 1986–2019 and amounted to 3.5 t/km2, while the suspended sediment yield in the Lena at the Tabaga gauging station slightly increased from 7 to 9.45 t/km2 per year.

This study presents new data on concentration of dissolved trace elements (DTE) in the Lena River–Laptev Sea mixing zone. Mean concentrations of some dissolved heavy metals in the mixing zone of fresh waters of the Lena River and sea waters of the Laptev Sea on the middle shelf and on the outer shelves are: 0.7± 0.05 μМ and 0.5 ± 0.04 μМ for Fe, 0.06 ± 0.01 μМ and 0.07 ± 0.01 μМ for Ni, 0.01 ± 0.003 μМ and 0.003 ± 0.002 μМ for Zn, 59.2 ± 7.4 nМ and 73.4 ± 12.8 nМ for Cu, respectively. Two major groups of DTE distribution were revealed according to their spatial behavior. The Li, V, As, Rb, Sr, Mo, U concentrations increase towards the outer shelf with increasing salinity. In contrast, mean concentrations of Al, Ti, Mn, Fe, Co decrease with increasing distance from the coast. The identified transport of freshwaters to a distance of 400 km is reflected in the distribution of DTE, which suggests that these elements are able to reach to the Central Arctic Ocean. • The Lena River runoff is the main source of dissolved heavy metals entering the Laptev Sea. • Increased concentrations of Fe, Zn, Cu, Cd and Pb in the Laptev Sea were observed in the 400 km from the Lena Delta. • Concentrations of Cd and Pb on the Laptev Sea middle shelf are higher than those in the mouths of the Ob and Yenisei rivers. [ABSTRACT FROM AUTHOR]

The distribution of the shrubby alder Duschekia fruticosa (Rupr.) Pouzar at the northern boundary, on the right bank of the Lena river in Ust’-Lenskiy nature reserve in Yakutia has been studied. Shrubby alder stands growing in 11 landscape-topological compartments of the area: along the banks of the Lena river, between the Tit-Ary island and the mouth of the Chinke river; ibid, between the mouth of the Chinke river and the mouth of the Sobol’-Yuryage river, ibid, below the mouth of the Sobol’-Yuryage river; on the banks and in the floodplain of the Chinke and Sobol’-Yuryage rivers and on the islands of the Lena delta. On the right bank of the Lena river between the Tit-Ary island and the mouth of the Chinke river shrubby alder groves stretch with small gaps, and downstream of the Lena river they are fragmentary, represented by limited, usually undersized brakes within the predominant tundra spaces. The maximum site of individual shrubby alder plants east of the bank of the Lena river is 2.2 km. The locations of growth of this species in the continental part of the nature reserve, in the north correspond to the coordinates of 72°12′22.6″N, 126°57′53.7″E; in the east - 72°06′33.1″N, 127°02′38.5″E and in the delta of the Lena river, on Samoylovskiy island – 72°23′15″N, 126°28′37″E. The altitudinal boundary of the distribution of shrubby alder in the mountainous part of the studied area is 30–50 m a. s. l. The conservation regime of the territory prevents anthropogenic influence on the natural process of moving shrubby alder to the north, which makes it possible to organize and conduct long-term monitoring observations of the dynamics of forest vegetation in the far north. The published results represent the second part of the cycle of authors’ publications devoted to the study of forest boreal flora in the tundra zone of Yakutia, downstream of the Lena river.

The distribution of the Cayander larch Larix cajanderi Mayr within the northern boundary, on the right bank of the Lena river in Ust’-Lenskiy nature reserve in Yakutia is discussed in the article. In the studied area, normal, curved, curtain, semi-shelter and elfin forms of growth of the Cajander larch were recorded, and the geographical coordinates of their locations are given. Larch communities are distributed over 6 ecological-topological areas of the terrain: along the banks of the Lena river, between the Tit-Ary island and the mouth of the Chinke river; in the interfluve of the Chinke and Sobol’-Yuryage rivers; below the mouth of the Sobol’-Yuryage river; on the left bank of the Chinke river valley; on the right bank of the valleys of the Chinke and Chinke Salata rivers. On the right bank of the Lena river between the Tit-Ary island and upstream from the mouth of the Chinke river, larch forests are common with small gaps. Their last locations are found in the mouth part of the Chinke river. In the interfluve between the Chinke and Sobol’-Yuryage rivers there is a small number of semi-elfin forest growth forms of larch trees. The last reliably registered larch communities were found at a distance of 2.1 km below the mouth of the Sobol’-Yuryage river. On the left bank of the Chinke river valley, on the slopes of the northern exposure, 5 locations of larch were found. All of them are located below the confluence of the Chinke-Yuryage and the Chinke-Salata rivers, at a distance from the Lena river up to 1.4 km. On the right side of the valley of the Chinke and the Chinke-Yuryage rivers, on the slopes of the southern exposition, larch communities are more common and were observed at a distance of 3 km from the Lena river to (thirteen locations). In the valley of the Chinke-Salata river larch is found only in one place, on the slope of the southern exposure, at a distance of 0.5 km from the confluence with the Chinke-Yuryage river. The conservation regime of the territory eliminates the anthropogenic impact on the natural process of larch moving to the north, which makes it possible to organize and conduct long-term monitoring observations of the dynamics of forest vegetation in the far north.

Diatoms from small waterbodies of polygonal microrelief tundra on Tit-Ary Island (the lower reaches of the Lena River) have been studied using scanning electron microscopy (SEM) for the first time. A total of 160 taxa belonging to 48 genera, 25 families, 13 orders, and 3 classes—including 55 taxa new for the flora of the Lena river basin, 46 taxa new for Yakutia, and 13 taxa identified only to the genus—have been found in the phytoperiphyton. The highest diversity of Bacillariophyta is found in a shallow lake at the north end of the island. More than 100 species and varieties of diatoms are detected there, including 29 species and varieties new for the flora of Yakutia. Achnanthidium minutissimum,Caloneis silicula, Cocconeis euglypta, C. pediculus, C. placentula, Cymbella artica, C. neocistula, Eunotia faba, E. praerupta, Gomphonema acuminatum, Hantzschia amphioxys, Navicula cryptocephala, Stauroneis anceps, Tabellaria fenestrata, T. flocculosa, Ulnaria ulna, and Caloneis silicula were found to be dominant in the waterbodies under study. [ABSTRACT FROM AUTHOR]

Warming air temperatures, shifting hydrological regimes and accelerating permafrost thaw in the catchments of the Arctic rivers is affecting their biogeochemistry. Arctic river monitoring is necessary to observe changes in the mobilization of dissolved organic matter (DOM) from permafrost. The Lena River is the second largest Arctic river and 71% of its catchment is continuous permafrost. Biogeochemical parameters, including temperature, electrical conductivity (EC), stable water isotopes, dissolved organic carbon (DOC) and absorption by colored dissolved organic matter (aCDOM) have been measured as part of a new high-frequency sampling program in the central Lena River Delta. The results show strong seasonal variations of all biogeochemical parameters that generally follow seasonal patterns of the hydrograph. Optical indices of DOM indicate a trend of decreasing aromaticity and molecular weight from spring to winter. High-frequency sampling improved our estimated annual fluvial flux of annual dissolved organic carbon flux (6.79 Tg C). EC and stable isotope data were used to distinguish three different source water types which explain most of the seasonal variation in the biogeochemistry of the Lena River. These water types match signatures of (1) melt water, (2) rain water, and (3) subsurface water. Melt water and rain water accounted for 84% of the discharge flux and 86% of the DOC flux. The optical properties of melt water DOM were characteristic of fresh organic matter. In contrast, the optical properties of DOM in subsurface water revealed lower aromaticity and lower molecular weights, which indicate a shift toward an older organic matter source mobilized from deeper soil horizons or permafrost deposits. The first year of this new sampling program sets a new baseline for flux calculations of dissolved matter and has enabled the identification and characterization of water types that drive the seasonality of the Lena River water properties.

The Lena River (Lena R.) heat flux affects the Laptev Sea hydrology. Published long-term estimates range from 14.0 to 15.7 EJ·a-1, based on data from Kyusyur, at the river outlet. A novel daily stream temperature (Tw) dataset was used to evaluate contemporary Lena R. heat flux, which is 16.4± 2.7 EJ·a-1 (2002-2011), confirming upward trends in both Tw and water runoff. Our field data from Kyusyur, however, reveal a significant negative bias, -0.8 °C in our observations, in observed Tw values from Kyusyur compared to the cross-section average Tw. Minor Lena R. tributaries discharge colder water during July-September, forming a cold jet affecting Kyusyur Tw data. Major Tw negative peaks mostly coincide with flood peaks on the Yeremeyka River, one of these tributaries. This negative bias was accounted for in our reassessment. Revised contemporary Lena R. heat flux is 17.6± 2.8 EJ·a-1 (2002-2011) and is constrained from above at 26.9 EJ·a-1 using data from Zhigansk, approximately 500 km upstream Kyusyur. Heat flux is controlled by stream temperature in June, during the freshet period, while from late July to mid-September, water runoff is a dominant factor. [ABSTRACT FROM AUTHOR]

The information is presented on hydrochemical studies performed in August 2018 at the middle and lower reaches of the Lena River from Yakutsk to Kyusyur settlements. The studies resulted in generating the database containing 80 parameters of water chemical composition including the stable isotopes of water, particulate matter, and DOC. The results obtained made it possible for the quantitative evaluation of the fluxes of dissolved and particulate matter from the headwaters towards the mouth of the Lena River and to ascertain the regularities in the transformation of these fluxes. [ABSTRACT FROM AUTHOR]

The current taxonomic composition, structure, and quantitative characteristics of zooplankton in channels of the mouth region of the Lena River were considered. The community of summer zooplankton in the Lena channels included 34 zooplanktonic species belonging to 18 families and 29 genera. Rotifers, as the most diverse and abundant group, provided a basis for the species diversity. It was found that the zooplanktonic community of the Lena channels is characterized by the low values of species diversity and quantitative characteristics.

Abstract Silicon isotope values (δ30Si DSi) of dissolved silicon (DSi) have been analyzed in the Lena River and its tributaries, one of the largest Arctic watersheds in the world. The geographical and temporal variations of δ30Si DSi range from +0.39 to +1.86‰ with DSi concentrations from 34 to 121 μM. No obvious patterns of DSi concentrations and δ30Si DSi values were observed along over 200 km of the two major tributaries, the Viliui and Aldan Rivers. In summer, the variations of DSi concentrations and δ30Si DSi values in the water are either caused by biological uptake by higher plants and phytoplankton or by mixing of water masses carrying different DSi concentrations and δ30Si DSi values. DSi in tributaries from the Verkhoyansk Mountain Range seems to be associated with secondary clay formation that increased the δ30Si DSi values, while terrestrial biological production is likely more prevalent in controlling δ30Si DSi values in Central Siberian Plateau and Lena Amganski Inter-River Area. In winter, when soils were frozen, the δ30Si DSi values in the river appeared to be controlled by weathering and clay formation in deep intrapermafrost groundwater. During the spring flood, dissolved silicate materials and phytoliths were flushed from the upper thawed soils into rivers, which reset δ30Si DSi values to the values observed prior to the biological bloom in summer. The results indicate that the Si isotope values reflect the changing processes controlling Si outputs to the Lena River and to the Arctic Ocean between seasons. The annual average δ30Si DSi value of the Lena Si flux is calculated to be +0.86 ± 0.3‰ using measured δ30Si DSi values from each season. Combined with the estimate of +1.6 ± 0.25‰ for the Yenisey River, an updated δ30Si DSi value of the major river Si inputs to the Arctic Ocean is estimated to be +1.3 ± 0.3‰. This value is expected to shift towards higher values in the future because of the impacts from a variety of biological and geochemical processes and sources under global warming. [ABSTRACT FROM AUTHOR]

We present an updated list of terrestrial and freshwater nematodes from all regions of the Arctic, for which records of properly identified nematode species are available: Svalbard, Jan Mayen, Iceland, Greenland, Nunavut, Northwest territories, Alaska, Lena River estuary, Taymyr and Severnaya Zemlya and Novaya Zemlya. The list includes 391 species belonging to 146 genera, 54 families and 10 orders of the phylum Nematoda.

Global warming in permafrost areas is expected to change fluxes of riverine organic carbon (OC) to the Arctic Ocean. Here OC concentrations, stable carbon isotope signatures (δ13C), and carbon-nitrogen ratios (C/N) are presented from 22 sampling stations in the Lena River and 40 of its tributaries. Sampling was conducted during two expeditions: the first in July 2012 in the south and southeastern region and the second in June 2013 in the northern region of the Lena basin. The data showed significant spatial differences in concentrations and major sources of OC. Mean subcatchment slopes were correlated with OC concentrations, implying that mountainous areas in general had lower concentrations than lowland areas. δ13C and C/N data from tributaries originating in mountainous areas indicated that both dissolved and particulate OC (DOC and POC) were mainly derived from soil organic matter (SOM). In contrast, tributaries originating in lowland areas had larger contributions from fresh vegetation to DOC, while aquatically produced OC was the major source of POC. We suggest that these differences in dominant sources indicated differences in dominant flow pathways. Tributaries with larger influence of fresh vegetation probably had surficial flow pathways, while tributaries with more SOM influence had deeper water flow pathways. Thus, the future export of OC to the Arctic Ocean will likely be controlled by changes in spatial patterns in hydroclimatology and the depth of the active layers influencing the dominant water flow pathways in Arctic river basins. [ABSTRACT FROM AUTHOR]