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A comparative analysis of the content and composition of organic matter (OM) in samples of bottom sediments and subaqueous permafrost rocks by the concentration of organic carbon (OC), C/N ratio, and isotopic composition of OC (δ13C) was carried out for three boreholes drilled in Buor-Khaya Bay in 2014–2015. The intervals of OC, C/N and δ13C values measured in 105 samples ranged from 0.04 to 23.1% (avg. 2.08%), from 1.00 to 41.7 (avg. 11.8) and from –29.1 to –19.6% (avg. –24.9%), respectively. The highest OC concentrations were found at horizons enriched with plant detritus. Based on the aggregate data obtained, it is shown that the studied sediments and permafrost rocks contain plant, lacustrine, and marine OM. In most samples, it is mixed, but enriched with of continental-vegetation and lacustrine components. According to the isotopic and elemental composition of the OM, it was found that sediments of the Yedoma Suite and Ice Complex are present in the studied strata, and to a lesser extent, deposits of thermokarst lakes and basins flooded by the sea. At a relative distance from the continent, isotopic heaviness of OC was recorded, associated with an increased share of aquatic components in OM, which is confirmed by data on the molecular composition of n-alkanes. There is no correlation between the grain size of sediments and measured organic geochemical parameters, which is a distinctive feature of the studied alluvial strata. [ABSTRACT FROM AUTHOR]

The emission of natural gas from the seafloor to the surface in shelf areas of the Arctic seas is of increasing interest among researchers. Recently, various types of acoustic instruments have been used to record streams of natural gas flowing out from the seafloor. Hydroacoustic and seismoacoustic equipment in various combinations was installed as an acoustic complex and has been successfully used on scientific cruises of RAS vessels in 2011–2021 in Russian Arctic shelf seas. This article addresses the issues of using the equipment for detecting areas of increased gas saturation and describes some of the results obtained. [ABSTRACT FROM AUTHOR]

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]

The paper presents the general lithological and geochemical characteristics of subsea permafrost and thawed bottom sediments from three cores drilled in Buor-Khaya Bay. The lithological, organic chemical, and microscopic data revealed spatial differences of Quaternary sedimentation and sedimentary evolution, which are determined by riverine dynamics, cryogenic processes, coastal abrasion, and ice activity in the studied part of the Laptev Sea. A variety of grain sizes and genetic types of deposits was revealed, most of which represented by alluvial sands. A large number of plant remains were found, which mainly contribute to the total organic carbon pool. The data indicate a pronounced polygenetic origin of the studied sediments, where the terrigenous supply of sedimentary material significantly dominates under alternating coastal Arctic morpholithogenesis conditions. [ABSTRACT FROM AUTHOR]