Organic carbon isotope ratios (δ13C) of Arctic Amerasian Continental shelf sediments

Organic matter origins are inferred from carbon isotope ratios ('¹³C) in recent continental shelf sediments and major rivers from 465 locations from the north Bering-Chukchi-East Siberian-Beaufort Sea, Arctic Amerasia. Generally, there is a cross-shelf increase in '¹³C, which is due to progressive increased contribution seaward of marine-derived organic carbon to surface sediments. This conclusion is supported by the correlations between sediment '¹³C, OC/N, and '¹⁵N. The sources of total organic carbon (TOC) to the Amerasian margin sediments are primarily from marine water-column phytoplankton and terrigenous C₃ plants constituted of tundra taiga and angiosperms. In contrast to more temperate regions, the source of TOC from terrigenous C₄ and CAM plants to the study area is probably insignificant because these plants do not exist in the northern high latitudes. The input of carbon to the northern Alaskan shelf sediments from nearshore kelp community (Laminaria solidungula) is generally insignificant as indicated by the absence of high sediment '¹³C values (-16.5 to -13.6‰) which are typical of the macrophytes. Our study suggests that the isotopic composition of sediment TOC has potential application in reconstructing temporal changes in delivery and accumulation of organic matter resulting from glacial-interglacial changes in sea level and environments. Furthermore, recycling and advection of the extensive deposits of terrestrially derived organic matter from land, or the wide Amerasian margin, could be a mechanism for elevating total CO₂ and pCO₂ in the Arctic Basin halocline.     

Mechanisms of Accumulation of Chemical Elements in a Peat Deposit in the Eastern Part of Vasyugan Swamp (West Siberia)

Doklady Earth Sciences - The results of mineralogical–geochemical studies of the oligotrophic pine–fruticulose–sphagnum segment of Vasyugan Swamp (West Siberia) in the winter of...     

Lithological and Geochemical Characteristics of Morpholithogenesis in Buor-Khaya Bay

Oceanology - 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...     

Variability of the carbonate system parameters in the coast-shelf zone of the East Siberian Sea during the autumn season

The publication presents the results of the studies on the carbonate system of the waters of the East Siberian Sea performed aboard R/V Ivan Kireev in September 2003–2004. It is shown that the aquatic area considered may be subdivided into two biohydrochemical provinces. The western part of the sea is a CO₂ supplier to the atmosphere, while its eastern part is a sink for CO₂. This is caused by the fact that the western part of the East Siberian Sea was affected by the waters of the southeastern part of the Laptev Sea, which were desalinated by riverine runoff, turbid, and enriched in the bioactive organic matter supplied into the water due to the coastal (and bottom) erosion. In the eastern part, cold waters of Pacific origin prevailed (saline, transparent, and productive), which caused a pronounced decrease in the partial pressure of CO₂(pCO₂) in the surface layer. In the frontal zone delimiting the desalinated shelf waters and those of the Pacific origin, the direction of the CO₂ flux between the atmosphere and the sea changed (from evasion to invasion). The interannual variability of the carbonate system parameters in the coastal-shelf zone of the East Siberian Sea was determined by the intensity of the propagation of the waters of different origins over the sea aquatic area caused by the atmospheric circulation, as well as by the riverine runoff intensity and the dynamics of erosion processes.     

CO<Subscript>2</Subscript> dynamics on the shelf of the East Siberian Sea

Expedition data obtained in the coastal-shelf zone of the East Siberian Sea in September 2003, 2004, and 2008 are generalized. Studies of carbonate system in water and CO₂ fluxes between ocean and atmosphere in this region confirmed that it was reasonable to divide the water area studied into two biogeochemical provinces and that the ecosystem of its coastal part is mainly of a heterotrophic nature. In different years, the extent of water supersaturation in carbon dioxide in the East Siberian Sea and the area of the CO₂ release significantly changed. Geographic localization of the atmosphere action centers over the Arctic and their intensity were main determining factors; that told both on the formation of a basic character of the atmospheric and hydrological processes and on the dynamics of the CO₂ exchange between water and air.     

Mineralogical and Geochemical Features of a Peat Deposit in the Eutrophic Obskoye Fen under Anthropogenic Load (Western Siberia)

Doklady Earth Sciences - The chemical composition and mineral inclusions in peats and the underlying soils of the eutrophic Obskoye fen (Western Siberia, Tomsk Region) are studied. The basic...     

Composition and genesis of the organic matter in the bottom sediments of the East Siberian Sea

The chemical composition of organic matter (C_org, N_org, δ¹³C, δ¹⁵N, and n-alkanes) was studied in the top layer of bottom sediments of the East Siberian Sea. Possible ways were proposed to estimate the amount of the terrigenous component in their organic matter (OM). The fraction of terrigenous OM estimated by the combined use of genetic indicators varied from 15% in the eastern part of the sea, near the Long Strait, to 95% in the estuaries of the Indigirka and Kolyma rivers, averaging 62% over the sea area.     

Isotope and geochemical parameters of hydrocarbon gases in bottom sediments of the shelf of the East Siberian Sea

The research results on gas geochemistry of hydrocarbon gases in bottom sediments of the East Siberian Sea are presented. The key isotope and geochemical parameters of syn- and epigenetic hydrocarbon gases are determined. The correlations between the molecular masses of hydrocarbon fractions and the carbon isotope composition on hydrocarbon gases of various origin are revealed.     

Assessment of the CO<Subscript>2</Subscript> fluxes between the ocean and the atmosphere in the eastern part of the Laptev Sea in the ice-free period

The carbonate system of waters of the inner, middle, and outer shelves was studied for a long period in the eastern part of the Laptev Sea. It is shown that the inner and middle shelves is a heterotrophic province and is a source of CO₂ to the atmosphere during August–September. The average CO₂ flux is 7.9 mmol m^–2 day^–1 and during one month waters of inner and middle shelves release into the atmosphere up to 0.7 Tg of carbon (C). The outer part of the shelf absorbs up to ~0.1 Tg C at an average rate of 3.9 mmol m^–2 day^–1 during the month. Generally, the ice-free zone of the eastern shelf of the Laptev Sea is a source of CO₂ in the studied season: the amount of C released into the atmosphere within a month is ~0.6 Tg.