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Grain-size and geochemical evidence for sediment transport mechanisms in the northeastern part of the East Siberian Sea and on the adjacent continental slope

2026-01-14T07:40:31Z

Title: Grain-size and geochemical evidence for sediment transport mechanisms in the northeastern part of the East Siberian Sea and on the adjacent continental slope Authors: Ovsepyan Ekaterina; Dorokhova Evgeniia; Ovsepyan Yaroslav; Aliev Ramiz; Jin, Young Keun Abstract: Grain-size analyses, end-member modeling, X-ray fluorescence, and radionuclide activity measurements were conducted on sediment minicores collected from the middle-outer shelf of the East Siberian Sea (ESS) and the upper part of the adjacent continental slope to elucidate the sedimentation mechanisms in this poorly studied region. The grain-size data demonstrate that clayey silt and silt strongly dominate on the ESS shelf and the continental slope. In contrast, sandy silt has a patchy distribution. End-member modeling, applied here for the first time, indicates that sea ice (frazil and anchor ice) rafting, and nepheloid transport are the primary processes responsible for distributing sedimentary material across the ESS. The XRF data confirm the results of previous studies, reporting a predominantly lithogenic origin for ESS deposits. Combined grain size and geochemical records suggests that the shelf break area serves as a depocenter for fine silt particles, likely supplied by nepheloid flow, and represents the most productive area in the northeastern ESS. High sea surface productivity likely results from influence of nutrient-rich Pacific-derived waters, the upwelling of transformed Atlanticderived waters, or a combination of both. The accumulation of the high amount of fine silt near the shelf break is suggested to be related to relatively calm bottom-water conditions, resulting from the potential interaction of the northward-flowing cross-shelf currents and episodic southward-moving compensatory flows. Wind direction is considered a key factor controlling the intensity of fine-grained material distribution by nepheloid flows and anchor ice across the ESS shelf. Sedimentation rates derived from the radionuclide activity measurements vary from 1.3 mm yr(-1) on the outer shelf to 1.0 mm yr(-1) on the upper continental slope.

Genesis of shallow-water manganese nodules with uniquely high Mn/Fe ratios

2026-01-14T07:37:18Z

Title: Genesis of shallow-water manganese nodules with uniquely high Mn/Fe ratios Authors: Koo Hyo Jin; Cho Hyen Goo; Jin, Young Keun; Lee Dong-Hun; Kim Ji-Hoon; Rhee, Tae Siek; Hong, Jong Kuk; Lee Sung Keun Abstract: While manganese (Mn) nodules are authigenic metal concretions that form predominantly on deep-sea seafloor, they have also been found along shallow seafloors. The formation environments of these nodules - deep sea vs. shallow water - often result in distinct chemical and morphological characteristics. As Mn is one of the essential components of energy-storing technologies, assessing the proper estimation of Mn and metal contents in both deep-and shallow-water Mn nodules is critical. It has been found that the Mn content of shallow-water nodules is often lower than that from deep-sea environments. Here, we report the discovery of shallow-water Mn nodules with exceptionally high Mn/Fe ratios on the continental slope of the East Siberian Sea, Arctic Ocean. Despite their shallow-water origin, Mn nodules show morphological and chemical characteristics that are typically unique to deep-sea nodules. These distinctive features, including exceptionally high Mn/Fe ratios, may reflect suboxic diagenesis and the preferential remobilization and re-precipitation of Mn from the adjacent continental shelf. The formation of high Mn/Fe nodules may reflect unique ocean circulation patterns that provided oxygenated bottom waters to the study area. Particularly, Pacific Water entering through the Bering Strait, which overlaps with the nodule formation depth (160-240 m) and is enriched in dissolved oxygen, could facilitate Mn-rich nodule growth under suboxic diagenetic conditions since the Holocene. Shallow-water Mn nodules with uniquely high Mn/Fe ratios may offer a novel paleo-environmental proxy for reconstructing paleohydrology and biogeochemical evolutions in shallow marine environments. (c) 2025 China University of Geosciences (Beijing) and Peking University. Published by Elsevier B.V. on behalf of China University of Geosciences (Beijing). This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Final Report(Project name: Investigation of submarine resource environment and seabed methane release in the Arctic)

2022-03-24T07:15:38Z

Title: Final Report(Project name: Investigation of submarine resource environment and seabed methane release in the Arctic) Authors: Jin, Young Keun

Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf

2022-03-24T07:15:16Z

Title: Subsea permafrost as a potential major source of dissolved organic matter to the East Siberian Arctic Shelf Authors: Chen, Meilian; Kim, Ji-Hoon; Lee, Yun Kyung; Lee, Dong-Hun; Jin, Young Keun; Hur, Jin Abstract: Arctic subsea permafrost contains more organic carbon than the terrestrial counterpart (similar to 1400 Pg C vs. similar to 1000 Pg C) and is undergoing fast degradation (at rates of similar to 10 to 30 cm yr(-1) over the past 3 decades) in response to climate warming. Yet the flux of organic carbon sequestered in the sediments of subsea permafrost to overlying water column, which can trigger enormous positive carbon-climate feedbacks, remain unclear. In this study, we examined the dissolved organic matter (DOM) diffusion to bottom seawaters from East Siberian Sea (ESS) sediments, which was estimated at about 943-2240 g C m(-2) yr(-1) and 10-55 g C m(-2) yr(-1) at the continuous-discontinuous transition zone of subsea permafrost and the remainder shelf and slope sites, respectively. The released DOM is characterized by prevailing dominance (>= 98%) of low molecular weight (M-D < 350 Da) fractions. A red-shifted (emission wavelength >500 nm) fluorescence fingerprint, a typical feature of sediment/soil DOM, accounts for 4-6% and 7-8% in the fluorescence distributions of seawaters and pore waters, respectively, on ESS shelf. Statistical analysis revealed that seawaters and pore waters possessed similar DOM composition. The estimated total benthic efflux of dissolved organic carbon (DOC) was similar to 0.7-1.0 Pg C yr(-1) when the estimate was scaled up to the entire Arctic shelf underlain with subsea permafrost assuming the width of continuous-discontinuous transition zone is 1 to 10 m. This estimation is consistent with the established similar to 10-30 cm yr(-1) degradation rates of subsea permafrost by estimating its thaw-out time. Compiled observation data suggested that subsea permafrost might be a major DOM source to the Arctic Ocean, which could release tremendous carbon upon remineralization via its degradation to CO2 and CH4 in the water column. (C) 2021 Elsevier B.V. All rights reserved.