Deglacial sea level history of the East Siberian Sea and Chukchi Sea margins

Deglacial (12.8–10.7 ka) sea level history on the East Siberian continental shelf and upper continental slope was reconstructed using new geophysical records and sediment cores taken during Leg 2 of the 2014 SWERUS-C3 expedition. The focus of this study is two cores from Herald Canyon, piston core SWERUS-L2-4-PC1 (4-PC1) and multicore SWERUS-L2-4-MC1 (4-MC1), and a gravity core from an East Siberian Sea transect, SWERUS-L2-20-GC1 (20-GC1). Cores 4-PC1 and 20-GC were taken at 120 and 115 m of modern water depth, respectively, only a few meters above the global last glacial maximum (LGM;  ∼  24 kiloannum or ka) minimum sea level of  ∼  125–130 meters below sea level (m b.s.l.). Using calibrated radiocarbon ages mainly on molluscs for chronology and the ecology of benthic foraminifera and ostracode species to estimate paleodepths, the data reveal a dominance of river-proximal species during the early part of the Younger Dryas event (YD, Greenland Stadial GS-1) followed by a rise in river-intermediate species in the late Younger Dryas or the early Holocene (Preboreal) period. A rapid relative sea level rise beginning at roughly 11.4 to 10.8 ka ( ∼  400 cm of core depth) is indicated by a sharp faunal change and unconformity or condensed zone of sedimentation. Regional sea level at this time was about 108 m b.s.l. at the 4-PC1 site and 102 m b.s.l. at 20-GC1. Regional sea level near the end of the YD was up to 42–47 m lower than predicted by geophysical models corrected for glacio-isostatic adjustment. This discrepancy could be explained by delayed isostatic adjustment caused by a greater volume and/or geographical extent of glacial-age land ice and/or ice shelves in the western Arctic Ocean and adjacent Siberian land areas

Carbonaceous material export from Siberian permafrost tracked across the Arctic Shelf using Raman spectroscopy

Warming-induced erosion of permafrost from Eastern Siberia mobilises large amounts of organic carbon and delivers it to the East Siberian Arctic Shelf (ESAS). In this study Raman spectroscopy of Carbonaceous Material (CM) was used to characterise, identify and track the most recalcitrant fraction of the organic load. 1463 spectra were obtained from surface sediments collected across the ESAS and automatically analysed for their Raman peaks. Spectra were classified by their peak areas and widths into Disordered, Intermediate, Mildly Graphitised and Highly Graphitised groups, and the distribution of these classes was investigated across the shelf. Disordered CM was most prevalent in a permafrost core from Kurungnakh Island, and from areas known to have high rates of coastal erosion. Sediments from outflows of the Indigirka and Kolyma rivers were generally enriched in Intermediate CM. These different sediment sources were identified and distinguished along an E-W transect using their Raman spectra, showing that sediment is not homogenised on the ESAS. Distal samples, from the ESAS slope, contained greater amounts of Highly Graphitised CM compared to the rest of the shelf, attributable to degradation or, more likely, winnowing processes offshore. The presence of all four spectral classes in distal sediments demonstrates that CM degrades much slower than lipid biomarkers and other traditional tracers of terrestrial organic matter, and shows that alongside degradation of the more labile organic matter component there is also conservative transport of carbon across the shelf toward the deep ocean. Thus, carbon cycle calculations must consider the nature as well as the amount of carbon liberated from thawing permafrost and other erosional settings

Macromolecular composition of terrestrial and marine organic matter in sediments across the East Siberian Arctic Shelf

Mobilisation of terrestrial organic carbon (terrOC) from permafrost environments in Eastern Siberia has the potential to deliver significant amounts of carbon to the Arctic Ocean, via both fluvial and coastal erosion. Eroded terrOC can be degraded during offshore transport, or deposited across the wide East Siberian Arctic Shelf (ESAS). Most studies of terrOC on the ESAS have concentrated on solvent-extractable organic matter, but this represents only a small proportion of the total terrOC load. In this study we have used pyrolysis gas chromatography mass spectrometry (py-GCMS) to study all major groups of macromolecular components of the terrOC; this is the first time that this technique has been applied to the ESAS. This has shown that there is a strong offshore trend from terrestrial Phenols, Aromatics, Cyclopentenones to marine Pyridines. There is good agreement between proportion Phenols measured using py-GCMS and independent quantification of lignin phenol concentrations (r2 = 0.67, p < 0.01, n = 24). Furfurals, thought to represent carbohydrates, show no offshore trend and are likely found in both marine and terrestrial organic matter. We have also collected new radiocarbon data for bulk OC (14COC) which, when coupled with previous measurements, allows us to produce the most comprehensive 14COC map of the ESAS to date. Combining the 14COC and py-GCMS data suggests that the Aromatics group of compounds is likely sourced from old, aged terrOC in contrast to the Phenols group, which is likely sourced from modern woody material. We propose that an index of the relative proportions of Phenols and Pyridines can be used as a novel terrestrial vs. marine proxy measurement for macromolecular organic matter. Principal component analysis found that various terrestrial vs. marine proxies show different patterns across the ESAS, and shows that multiple river-ocean transects of surface sediments transition from river-dominated to coastal erosion-dominated to marine-dominated signatures

Dynamical scaling law in the development of drift wave turbulence

Destabilization and degradation of permafrost carbon in the Arctic regions could constitute a positive feedback to climate change. A better understanding of its fate upon discharge to the Arctic shelf is therefore needed. In this study, bulk carbon isotopes as well as terrigenous and marine biomarkers were used to construct two centennial records in the East Siberian Sea. Differences in topsoil and Pleistocene Ice Complex Deposit permafrost concentrations, modeled using δ13C and δ14C, were larger between inner and outer shelf than the changes over time. Similarly, lignin-derived phenol and cutin acid concentrations differed by a factor of ten between the two stations, but did not change significantly over time, consistent with the dual-carbon isotope model. High molecular weight (HMW) n-alkane and n-alkanoic acid concentrations displayed a smaller difference between the two stations (factor of 3-6). By contrast, the fraction for marine OC drastically decreased during burial with a half-life of 19-27 years. Vegetation and degradation proxies suggested supply of highly degraded gymnosperm wood tissues. Lipid Carbon Preference Index (CPI) values indicated more extensively degraded HMW n-alkanes on the outer shelf with no change over time, whereas n-alkanoic acids appeared to be less degraded toward the core top with no large differences between the stations. Taken together, our results show larger across-shelf changes than down-core trends. Further investigation is required to establish whether the observed spatial differences are due to different sources for the two depositional settings or, alternatively, a consequence of hydrodynamic sorting combined with selective degradation during cross-shelf transport

Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect, East Siberian Sea

© The Authors, 2010. This article is distributed under the terms of the Creative Commons Attribution 3.0 License. The definitive version was published in Biogeosciences 7 (2010): 3153-3166, doi:10.5194/bg-7-3153-2010.Climate warming in northeastern Siberia may induce thaw-mobilization of the organic carbon (OC) now held in permafrost. This study investigated the composition of terrestrial OC exported to Arctic coastal waters to both obtain a natural integration of terrestrial permafrost OC release and to further understand the fate of released carbon in the extensive Siberian Shelf Seas. Application of a variety of elemental, molecular and isotopic (δ13C and Δ14C) analyses of both surface water suspended particulate matter and underlying surface sediments along a 500 km transect from Kolyma River mouth to the mid-shelf of the East Siberian Sea yielded information on the sources, degradation status and transport processes of thaw-mobilized soil OC. A three end-member dual-carbon-isotopic mixing model was applied to deduce the relative contributions from riverine, coastal erosion and marine sources. The mixing model was solved numerically using Monte Carlo simulations to obtain a fair representation of the uncertainties of both end-member composition and the end results. Riverine OC contributions to sediment OC decrease with increasing distance offshore (35±15 to 13±9%), whereas coastal erosion OC exhibits a constantly high contribution (51±11 to 60±12%) and marine OC increases offshore (9±7 to 36±10%). We attribute the remarkably strong imprint of OC from coastal erosion, extending up to ~500 km from the coast, to efficient offshoreward transport in these shallow waters presumably through both the benthic boundary layer and ice-rafting. There are also indications of simultaneous selective preservation of erosion OC compared to riverine OC. Molecular degradation proxies and radiocarbon contents indicated a degraded but young (Δ14C ca. −60‰ or ca. 500 14C years) terrestrial OC pool in surface water particulate matter, underlain by a less degraded but old (Δ14C ca. −500‰ or ca. 5500 14C years) terrestrial OC pool in bottom sediments. We suggest that the terrestrial OC fraction in surface water particulate matter is mainly derived from surface soil and recent vegetation fluvially released as buoyant organic-rich aggregates (e.g., humics), which are subjected to extensive processing during coastal transport. In contrast, terrestrial OC in the underlying sediments is postulated to originate predominantly from erosion of mineral-rich Pleistocene coasts (i.e., yedoma) and inland mineral soils. Sorptive association of this organic matter with mineral particles protects the OC from remineralization and also promotes rapid settling (ballasting) of the OC. Our findings corroborate recent studies by indicating that different Arctic surface soil OC pools exhibit distinguishing susceptibilities to degradation in coastal waters. Consequently, the general postulation of a positive feedback to global warming from degradation of permafrost carbon may be both attenuated (by reburial of one portion) and geographically displaced (degradation of released terrestrial permafrost OC far out over the Arctic shelf seas).The ISSS-08 program was supported by the Knut and Alice Wallenberg Foundation, Headquarters of the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council (VR Contract No. 621-2004-4039 and 621-2007-4631), the US National Oceanic and Atmospheric Administration (Siberian Shelf Study), the Russian Foundation of Basic Research (08-05-13572, 08-05-00191-a, and 07-05-00050a), the Swedish Polar Research Secretariat, the Arctic Co-Op Program of the Nordic Council of Ministers (331080-70219) and the National Science Foundation (OPP ARC 0909546). O¨ . G. also acknowledges financial support as an Academy Research Fellow from the Swedish Royal Academy of Sciences, L. S. a Marie Curie grant (contract no. PIEF-GA-2008-220424), T. E. an NSF grant (ARC-0909377) and A. A. support from the Knut and Alice Wallenberg Foundation

East Siberian Sea, an Arctic region of very high biogeochemical activity

Shelf seas are among the most active biogeochemical marine environments and the East Siberian Sea is a prime example. This sea is supplied by seawater from both the Atlantic and Pacific Oceans and has a substantial input of river runoff. All of these waters contribute chemical constituents, dissolved and particulate, but of different signatures. Sea ice formation during the winter season and melting in the summer has a major impact on physical as well as biogeochemical conditions. The internal circulation and water mass distribution is significantly influenced by the atmospheric pressure field. The western region is dominated by input of river runoff from the Laptev Sea and an extensive input of terrestrial organic matter. The microbial decay of this organic matter produces carbon dioxide (CO&lt;sub&gt;2&lt;/sub&gt;) that oversaturates all waters from the surface to bottom relative to atmospheric level, even when primary production, inferred from low surface water nutrients, has occurred. The eastern surface waters were under-saturated with respect to CO&lt;sub&gt;2&lt;/sub&gt; illustrating the dominance of marine primary production. The drawdown of dissolved inorganic carbon equals a primary production of ~0.8 &amp;plusmn; 2 mol C m&lt;sup&gt;−2&lt;/sup&gt;, which when multiplied by half the area of the East Siberian Sea, ~500 000 km&lt;sup&gt;2&lt;/sup&gt;, results in an annual primary production of 0.4 (&amp;plusmn; 1) × 10&lt;sup&gt;12&lt;/sup&gt; mol C or ~4 (&amp;plusmn; 10) &amp;times; 10&lt;sup&gt;12&lt;/sup&gt; gC. Microbial decay occurs through much of the water column, but dominates at the sediment interface where the majority of organic matter ends up, thus more of the decay products are recycled to the bottom water. High nutrient concentrations and fugacity of CO&lt;sub&gt;2&lt;/sub&gt; and low oxygen and pH were observed in the bottom waters. Another signature of organic matter decomposition, methane (CH&lt;sub&gt;4&lt;/sub&gt;), was observed in very high but variable concentrations. This is due to its seabed sources of glacial origin or modern production from ancient organic matter, becoming available due to sub-sea permafrost thaw and formation of so-called taliks. The decay of organic matter to CO&lt;sub&gt;2&lt;/sub&gt; as well as oxidation of CH&lt;sub&gt;4&lt;/sub&gt; to CO&lt;sub&gt;2&lt;/sub&gt; contribute to a natural ocean acidification making the saturation state of calcium carbonate low, resulting in under-saturation of all the bottom waters with respect to aragonite and large areas of under-saturation down to 50 % with respect to calcite. Hence, conditions for calcifying organisms are very unfavorable

Исследование огнезащищенных фанерных плит на горючесть и токсичность

Ціль роботи порівняльне вивчення звичайних фанерних плит, а також просочених вогнебіозахистною сумішю, яка складається із суміши сольового антипирену та полімерного антисептика ДСА 2, а також гідрофобізуючого препарату «Силол» на горючість та токсичність. В ході роботы було показано, що фанерна плита, яку оброблено вогнебіозахистною сумішю, по показникам горючості та токсич ності значно превосходить не оброблену фанеру.The target of the work is comparative study of plywood — ordinary and pretreated by salt fire retardant and polymeric antiseptic ДСА 2 mixture with hydrophobying composition «Силол» — for the combustibility and the toxicity. It was shown that pretreated plywood is more toxic and less combustible

Organic carbon in surface sediments of Chaunskaya Bay (East Siberian Sea): results of pyrolytic analysis using the Rock-Eval method

Relevance. Dictated by the need to assess functioning of the biogeochemical regime of the Arctic region by studying geochemical properties of organic matter of bottom sediments on the example of the Chaunskaya Bay (East-Siberian Sea). Aim. To study the spatial variability of geochemical parameters of organic matter of bottom sediments of the Chaunskaya Bay using the Rock-Eval method, as well as to identify a possible relationship between the parameter TOC and the pelite fraction. Objects. Samples of bottom sediments of the Chaunskaya Bay (East Siberian Sea). Sampling took place in stages from three horizons (upper 0–2 cm, intermediate 2–5 cm, lower 5–10 cm) during a comprehensive scientific expedition to the R/V "Academician Oparin" in September–October 2020. Methods. Granulometric composition of bottom sediments was determined using the Analysette 22 NanoTec particle analyzer (Fritsch, Germany). The analysis of hydrocarbon compounds of organic matter was performed using pyrolytic analysis on the device (Rock Eval 6 Turbo of Vinci Technologies, France). Results. The results of pyrolytic analysis considered by the authors have shown that such factors as the primary productivity of the waters of the studied water area and the processes of erosion of the coastal zone play a decisive role in the formation of the composition of the TOC in bottom sediments of the Chaunskaya Bay. We also do not exclude the contribution of river runoff to the composition of the TOC in bottom sediments; however, we consider it small due to the insignificant inflow of river sediments into the waters of the studied area. The pyrolytic data obtained by us indicate that both the marine component (primary productivity) and the terrigenous component (erosion of the coastal complex) are present in the composition of the TOC in bottom sediments of the studied area