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https://doi.org/10.5194/bg-2019-470
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2019-470
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 03 Jan 2020

Submitted as: research article | 03 Jan 2020

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This preprint is currently under review for the journal BG.

Organic Carbon Characteristics in Ice-rich Permafrost in Alas and Yedoma Deposits, Central Yakutia, Siberia

Torben Windirsch1,2, Guido Grosse1,2, Mathias Ulrich3, Lutz Schirrmeister1, Alexander N. Fedorov4,5, Pavel Ya. Konstantinov4, Matthias Fuchs1, Loeka L. Jongejans1,2, Juliane Wolter1, and Jens Strauss1 Torben Windirsch et al.
  • 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Telegrafenberg A45, 14473 Potsdam, Germany
  • 2University of Potsdam, Institute of Geosciences, Karl-Liebknecht-Straße 24-25, 14476 Potsdam, Germany
  • 3Leipzig University, Institute for Geography, Johannisallee 19a, 04103 Leipzig, Germany
  • 4Melnikov Permafrost Institute, SB RAS, 36 Merzlotnaya str., Yakutsk, Republic of Sakha, Russia, 677010
  • 5BEST International Centre, North-Eastern Federal University, 58 Belinsky str., Yakutsk, Republic of Sakha, Russia, 677027

Abstract. Permafrost ground is one of the largest repositories of stored terrestrial natural carbon and might become a carbon source with ongoing global warming. In particular, syngenetically frozen ice-rich Yedoma deposits originating from the late Pleistocene store a large amount of carbon. This carbon has not yet become part of the recent carbon cycle. With this study of Yedoma and associated Alas deposits in Central Yakutia we aim to understand the local sediment genesis and its effect on permafrost carbon storage. For this purpose, we investigated the Yukechi Alas area (61.76495° N, 130.46664° E), a thermokarst landscape degrading into Yedoma in Central Yakutia. Two sediment cores (Yedoma upland, 22.35 m depth, and Alas basin, 19.80 m depth) were drilled in 2015. We analyzed for ice content, total carbon and total nitrogen content, total organic carbon content, stable oxygen and hydrogen isotopes, stable carbon isotopes, mass specific magnetic susceptibility, grain size distribution, and radiocarbon ages. Samples taken from both cores were radiocarbon-dated up to 50,000 years before present. The laboratory analyses of both cores revealed very low carbon contents down to several meters depth. Those core parts holding very little to no detectable carbon consist of coarser sandy material estimated to an age between 39,000 and 18,000 years before present. For this period we assume sediment input of organic-poor material. Water isotope data derived from pore ice within the Yedoma core indicate a continuously cold state of the lower core parts, thereby ruling out a potential theory of Holocene influence. In consequence, we conclude that no strong organic matter decomposition took place in the sediments of the Yedoma core until today. In contrast, the Alas core from an adjacent thermokarst basin was strongly disturbed by lake development and permafrost thaw, and accordingly its sediment and carbon characteristics differed from those of the Yedoma core. The Alas core shows homogeneous ice content and the water isotope characteristics of a slightly more decomposed organic material; the findings of very carbon-poor core sections from the Yedoma core can be duplicated. The Yedoma deposition was likely influenced by fluvial regimes in nearby streams and the Lena River shifting with climate. The low carbon content and the clear stratigraphical layering of different sediment types suggest that the Yedoma deposits in the Yukechi area differ from other Yedoma sites regarding carbon stock and sedimentological composition. We conclude that sedimentary composition and deposition regimes of Yedoma may differ significantly within the Yedoma domain. The resulting heterogeneity should be taken into account for upscaling approaches on the Yedoma carbon stock. The Alas core gives clear insights into the future development of Cenral Yakutian Yedoma deposits.

Torben Windirsch et al.

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Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Torben Windirsch et al.

Data sets

Organic material, sediment and ice characteristics of two permafrost cores from Yukechi Alas, Central Yakutia T. Windirsch, G. Grosse, M. Ulrich, L. Schirrmeister, A. Fedorov, P. Konstantinov, M. Fuchs, and J. Strauss https://doi.org/10.1594/PANGAEA.898754

Torben Windirsch et al.

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Short summary
To assess the circumarctic permafrost carbon storage in more detail, we examined two permafrost deposit types in Central Yakutia. We found only little and mainly undecomposed organic carbon in those deposits as a result of largely changing sedimentation processes. The carbon stock of the examined Yedoma deposits is only about 25 % of general Yedoma estimations. This implies a very heterogeneous Yedoma composition. High ice contents indicate a high vulnerability to degradation by global warming.
To assess the circumarctic permafrost carbon storage in more detail, we examined two permafrost...
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