Organic matter characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, west Alaska

Jongejans, Loeka L.; Strauß, Jens; Lenz, Josefine; Peterse, Francien; Mangelsdorf, Kai; Fuchs, Matthias; Grosse, Guido

doi:10.5194/bg-15-6033-2018

Cited by 44 publications

(49 citation statements)

References 68 publications

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“…On the other hand, it could simply reflect low input. In our case, we argue that the stable carbon isotope data of our cores, assuming that the source signal was more or less constant with time, are between -24.06 and -27.24 ‰ and are at the low end, but comparable to other studied sites from the Yedoma domain (Schirrmeister et al, 2013;Strauss et al, 2013;Jongejans et al, 2018). Both cores show the lowest δ 13 C values closest to the surface as the organic material is the most recent and therefore least decomposed.…”

Section: Carbon Accumulation and Loss At The Yukechi Study Sitesupporting

confidence: 65%

“…Assessing the carbon inventory of the full-length Central Yakutian cores examined in this study, we estimated an organic carbon density of 5.27 ± 1.42 kg/m³ for the sediments of the YED1 core down to a depth of 22.12 m bs, excluding the ice wedge. The organic carbon density at this site is approximately four times lower than estimated in previous studies of deep Yedoma deposits (Strauss et al, 2012;Shmelev et al, 2017;Jongejans et al, 2018). This also shows that, even when including roughly 10 m of organic carbon-free material, large portions of organic carbon must be stored below 3 m, as the organic carbon density increases from measurements of the top 3 m to measurements of the whole core.…”

Section: Central Yakutian Yedoma Deposits In a Circumarctic And Regiocontrasting

confidence: 42%

“…Strauss et al (2017) calculated a mean organic carbon density for the upper 3 m of Yedoma deposits in the Lena-Aldan interfluve of 25 to 33 kg/m 3 . Using a bootstrapping approach after Jongejans et al (2018), based on our measured values we found a much lower organic carbon density of 4.48 ± 1.43 kg/m 3 for the top 3 m of the YED1 core. For Alas1, an organic carbon density of 6.93 ± 2.90 kg/m 3 was calculated for the top 3 m. This results in a mean organic carbon density of only 4.40 kg/m 3 for the top 3 m of dry soil at the Yukechi study site.…”

Section: Central Yakutian Yedoma Deposits In a Circumarctic And Regiomentioning

confidence: 87%

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

Windirsch¹,

Grosse²,

Ulrich³

et al. 2020

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<p><strong>Abstract.</strong> 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&#176;&#8201;N, 130.46664&#176;&#8201;E), a thermokarst landscape degrading into Yedoma in Central Yakutia. Two sediment cores (Yedoma upland, 22.35&#8201;m depth, and Alas basin, 19.80&#8201;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.</p>

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Section: Carbon Accumulation and Loss At The Yukechi Study Sitesupporting

confidence: 65%

Section: Central Yakutian Yedoma Deposits In a Circumarctic And Regiocontrasting

confidence: 42%

Section: Central Yakutian Yedoma Deposits In a Circumarctic And Regiomentioning

confidence: 87%

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

Windirsch¹,

Grosse²,

Ulrich³

et al. 2020

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“…Yedoma is ice-rich (50-90 vol %, volume percent, ice) and usually has organic carbon contents of 2-4 wt % (weight percent) with an estimated deposit thickness of up to 40 m (Schirrmeister et al, 2013;Strauss et al, 2013). In central Yakutia, the cryostratigraphic characteristics of these syngenetic Late Pleistocene deposits have been previously studied by various researchers (Soloviev, 1959;Katasonov and Ivanov, 1973;Katasonov, 1975;Péwé et al, 1977;Péwé and Journaux, 1983). In the context of global climate change, such a high ice content, with intrasedimental ice and syngenetic ice wedges, renders Yedoma deposits highly vulnerable to thaw-induced landscape changes (Schirrmeister et al, 2013) and ground volume loss causing surface subsidence.…”

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confidence: 99%

Organic carbon characteristics in ice-rich permafrost in alas and Yedoma deposits, central Yakutia, Siberia

et al. 2020

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Abstract. Permafrost ground is one of the largest repositories of terrestrial organic carbon and might become or already is a carbon source in response to ongoing global warming. With this study of syngenetically frozen, ice-rich and organic carbon (OC)-bearing Yedoma and associated alas deposits in central Yakutia (Republic of Sakha), we aimed to assess the local sediment deposition regime and its impact on permafrost carbon storage. For this purpose, we investigated the Yukechi alas area (61.76495∘ N, 130.46664∘ E), which is a thermokarst landscape degrading into Yedoma in central Yakutia. We retrieved two sediment cores (Yedoma upland, 22.35 m deep, and alas basin, 19.80 m deep) in 2015 and analyzed the biogeochemistry, sedimentology, radiocarbon dates and stable isotope geochemistry. The laboratory analyses of both cores revealed very low total OC (TOC) contents (<0.1 wt %) for a 12 m section in each core, whereas the remaining sections ranged from 0.1 wt % to 2.4 wt % TOC. The core sections holding very little to no detectable OC consisted of coarser sandy material were estimated to be between 39 000 and 18 000 BP (years before present) in age. For this period, we assume the deposition of organic-poor material. Pore water stable isotope data from the Yedoma core indicated a continuously frozen state except for the surface sample, thereby ruling out Holocene reworking. In consequence, we see evidence that no strong organic matter (OM) decomposition took place in the sediments of the Yedoma core until today. The alas core from an adjacent thermokarst basin was strongly disturbed by lake development and permafrost thaw. Similar to the Yedoma core, some sections of the alas core were also OC poor (<0.1 wt %) in 17 out of 28 samples. The Yedoma deposition was likely influenced by fluvial regimes in nearby streams and the Lena River shifting with climate. With its coarse sediments with low OC content (OC mean of 5.27 kg m−3), the Yedoma deposits in the Yukechi area differ from other Yedoma sites in North Yakutia that were generally characterized by silty sediments with higher OC contents (OC mean of 19 kg m−3 for the non-ice wedge sediment). Therefore, we conclude that sedimentary composition and deposition regimes of Yedoma may differ considerably within the Yedoma domain. The resulting heterogeneity should be taken into account for future upscaling approaches on the Yedoma carbon stock. The alas core, strongly affected by extensive thawing processes during the Holocene, indicates a possible future pathway of ground subsidence and further OC decomposition for thawing central Yakutian Yedoma deposits.

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“…Thus, besides the quantification of organic C (OC), there is a growing number of studies aiming to elucidate the chemical composition of SOM and the processes and mechanisms involved in C 55 cycling and stabilization in permafrost-affected soils (i.a. Torn et al, 2013;Mueller et al, 2015;Strauss et al, 2017;Jongejans et al, 2018;Kuhry et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils

Prater¹,

Zubrzycki²,

Buegger³

et al. 2020

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Abstract. Permafrost-affected soils of the Arctic account for 70 % or 727 Pg of the soil organic carbon (C) stored in the permafrost region and therefore play a major role in the global C cycle. Most studies on the budgeting of C storage and the quality of soil organic matter (SOM) in the northern circumpolar region focus on bulk soils. Thus, although there is a plethora of assumptions regarding differences in terms of C turnover or stability, only little knowledge is available on the mechanisms stabilizing organic C in Arctic soils besides impaired decomposition due to low temperatures. To gain such knowledge, we investigated soils from Samoylov Island in the Lena River Delta with respect to the composition and distribution of organic C among differently stabilized SOM fractions. The soils were fractionated according to density and particle size to obtain differently stabilized SOM fractions differing in chemical composition and thus bioavailability. To better understand the chemical alterations from plant-derived organic particles in these soils rich in fibrous plant residues to mineral-associated SOM, we analysed the elemental, isotopic and chemical composition of particulate OM (POM) and clay-sized mineral-associated OM (MAOM). We demonstrate that the SOM fractions that contribute with about 17 kg C m−3 for more than 60 % of the C stock are highly bioaccessible and that most of this labile C can be assumed to be prone to mineralization under warming conditions. Thus, the amount of relatively stable, small occluded POM and clay-sized MAOM that account currently with about 10 kg C m−3 for about 40 % of the C stock will most probably be crucial for the quantity of C protected from mineralization in these Arctic soils in a warmer future. Using δ15N as proxy for nitrogen (N) balances indicated an important role of N inputs by biological N fixation, while gaseous N losses appeared less important. However, this could change, as with about 0.4 kg N m−3 one third of the N is present in bioaccessible SOM fractions, which could lead to increases in mineral N cycling and associated N losses under global warming. Our results highlight the vulnerability of SOM in Arctic permafrost-affected soils under rising temperatures, potentially leading to unparalleled greenhouse gas emissions from these soils.

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Organic matter characteristics in yedoma and thermokarst deposits on Baldwin Peninsula, west Alaska

Cited by 44 publications

References 68 publications

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

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

Organic carbon characteristics in ice-rich permafrost in alas and Yedoma deposits, central Yakutia, Siberia

From fibrous plant residues to mineral-associated organic carbon – the fate of organic matter in Arctic permafrost soils

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