the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
Assessing Organic Matter Characteristics in Ancient Permafrost: A Biogeochemical Study at the Batagay Megaslump, East Siberia
- 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, 14473 Potsdam, Germany
- 2Institute of Geosciences, University of Potsdam, 14476 Potsdam, Germany
- 3GFZ German Research Centre for Geosciences, Section Organic Geochemistry, 14473 Potsdam, Germany
- 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Polar Terrestrial Environmental Systems Section, 14473 Potsdam, Germany
- 5Cryolithology and Glaciology Department, Faculty of Geography, Lomonosov Moscow State University, 119991 Moscow
- 6Laboratory of Permafrost Landscapes, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk, Russia
- 7Laboratory of General Geocryology, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk
- acurrent address: Technische Universität Dresden, Institute of Geography, 01069 Dresden, Germany
- 1Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Permafrost Research Section, 14473 Potsdam, Germany
- 2Institute of Geosciences, University of Potsdam, 14476 Potsdam, Germany
- 3GFZ German Research Centre for Geosciences, Section Organic Geochemistry, 14473 Potsdam, Germany
- 4Alfred Wegener Institute Helmholtz Centre for Polar and Marine Research, Polar Terrestrial Environmental Systems Section, 14473 Potsdam, Germany
- 5Cryolithology and Glaciology Department, Faculty of Geography, Lomonosov Moscow State University, 119991 Moscow
- 6Laboratory of Permafrost Landscapes, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk, Russia
- 7Laboratory of General Geocryology, Melnikov Permafrost Institute, Siberian Branch of the Russian Academy of Science, 677010 Yakutsk
- acurrent address: Technische Universität Dresden, Institute of Geography, 01069 Dresden, Germany
Abstract. The Batagay megaslump, a permafrost thaw feature in northeastern Siberia, provides access to ancient permafrost up to ~650 ka old. We aimed to assess the permafrost-locked organic matter (OM) quality and to deduce paleoenvironmental information on glacial-interglacial timescales. We sampled five stratigraphic units exposed on the 55-m-high slump headwall and analyzed lipid biomarkers. Our findings revealed similar biogeochemical signatures for the glacial periods: the Lower Ice Complex (Marine Isotope Stage (MIS) 16 or earlier), the Lower Sand Unit (some time between MIS 16-6) and the Upper Ice Complex (MIS 4-2). The OM in these units has a terrestrial character, and microbial activity was likely limited. Contrarily, the n-alkane and fatty acid distributions differed for the units from interglacial periods: the Woody Layer (MIS 5), separating the Lower Sand and the Upper Ice Complex, and the Holocene Cover (MIS 1), on top of the Upper Ice Complex. The Woody Layer, marking an permafrost degradation disconformity, contained markers of terrestrial origin (sterols) and high microbial decomposition (iso- and anteiso-fatty acids). In the Holocene Cover, biomarkers pointed to wet depositional conditions and we identified branched and cyclic alkanes, which are likely of microbial or bacterial origin. Higher OM decomposition characterized the interglacial periods. As climate warming will continue permafrost degradation in the Batagay megaslump and in other areas, large amounts of deeply buried, ancient OM with a variable composition and degradability are mobilized, likely significantly enhancing greenhouse gas emissions from permafrost regions.
- Preprint
(1683 KB) -
Supplement
(1054 KB) - BibTeX
- EndNote
Loeka Laura Jongejans et al.
Status: open (until 10 Jun 2022)
-
RC1: 'Comment on tc-2022-12', Jack Hutchings, 02 May 2022
reply
Reviewer Comments
Jongejans et al. present a study that uses bulk and organic geochemical measurements to investigate the organic matter stored in the ~55 m headwall of the Batagay slump. This is quite intriguing as this slump is a unique insight into a long history of permafrost accumulation (and degradation) that may be useful for both understanding the evolution of permafrost landscapes as well as predicting future impacts of carbon stored in permafrost sediments as the environment is transformed by anthropogenic climate change. Overall, I find their manuscript to be well-written and quite detailed, but not overly long. I deeply appreciate the technical detail presented in the biomarker work (Table 2 is a delight) that is sometimes overlooked or omitted by organic geochemists.
I have relatively few questions and comments as this paper seems to fit nicely into the recent series of papers involving the ongoing investigation of the Batagay slump. Here are a few worth considering:
- The authors note that the interglacial units appear to have “decreased OM quality” whereas the glacial periods have “variable but overall higher OM quality”. This makes sense when thinking about relative temperature and rates of cycling and, perhaps, the different residence time of OM within the active layer where OM degradation occurs. However, the OM stock sizes between the interglacial and glacial periods must be quite different. Therefore, we might consider the differing consequences of releasing a relatively small amount of “fresh” glacial-era OM compared to relatively large amounts of “degraded” interglacial-era OM. Additionally, regardless of the characteristics of sediment-bound particulate OM, the Woody Layer contains, of course, wood and other plant detritus that will be readily remineralized upon thaw.
- Related to the above, I think a worthwhile and interesting calculation would be to estimate (even roughly) the relative sizes of C stocks within each of the types of units. If we could estimate the average C stock (i.e., organic C density per unit area) of these units, could we then also estimate (again, roughly) the amount of C mobilized by the Batagay slump since its formation?
- Combined with stock estimates, the authors could incorporate some of the biomarker-based degradation insights to categorize the pools of carbon mobilized as either “pre-processed” or “fresh” to perhaps get some insight into if we expect the mobilized material to be quickly remineralized or simply redeposited downstream. Combining this with knowledge of other thaw slumps could be useful for developing some insights into the consequences of this type of extreme thaw into local (nutrient loading), regional (source of deltaic organic matter), and even global (atmospheric) carbon cycles.
- This may be more appropriate for a different article (perhaps one with a stronger focus on cryostratigraphy and geomorphology), but, is the size/scale of Batagay a unique feature? Retrogressive thaw slumps are well-studied and widely documented, but the scale of Batagay is quite impressive. While we can expect that as we warm the Arctic, we will have more thaw-related features, will we expect more Batagay-scale slumps? And, do we think there is anything unique in terms of biogeochemical cycling and/or consequences for local/downstream ecosystems of a single Batagay-scale slump versus multiple, smaller slumps whose total volume of mobilized permafrost might be similar to Batagay?
- The authors note that an unconformity exists between the Lower Sand Unit and the Woody Layer and that the Woody Layer occupies erosional gullies that formed during the last interglacial. While I realize precise dating of accumulation rates is difficult, I would be curious to see an estimate of the amount of carbon mobilized from the Lower Sand Unit due to the warming-induced erosional processes during the last interglacial.
-
RC2: 'Comment on tc-2022-12', Anonymous Referee #2, 08 May 2022
reply
Permafrost soils store more than 30% of the global surface organic carbon. The thaw-induced carbon release in the form of greenhouse gases would create a positive feedback to amplify climate warming. In this paper, Jongejans et al., present the valuable records of TOC, TN and multiple lipid biomarkers to assess organic matter quality in a 650-ka ancient permafrost of east Siberia. Such old records cover glacial-interglacial climate variations, which provides a valuable opportunity to explore potential influence of climate changes on permafrost carbon cycling. Their biomarker evidences show higher organic matter decomposition during interglacial periods. This will be very useful for understanding of carbon cycles in permafrost regions as global climate warms. I have no major comments on this valuable paper and hence recommend to accept it after the following minor/moderate comments have been covered.
L22: Add what lipid biomarkers did you analyze in this study, such as alkanes, fatty acids.
L29: Delete “or bacterial”. Microbial origin contains bacterial origin.
L36: the world’s surface soil carbon?
L57-58: Biomarker tools as tracing permafrost thaw and carbon cycling are very important in this study. I suggest more previous publications are needed to introduce here. Multiple lipid biomarkers have been applied to sediment records for reconstructing carbon perturbations of permafrost (e.g., Evert et al. 2016, https://doi.org/10.1177/0959683616645942; Yao et al., 2021, https://doi.org/10.1130/G48891.1).
L115: What solvents (including solvent volume) do you use for separation the aliphatic, aromatic and polar NSO?
L127: The first mention of abbreviation “FA” is fatty acids?
L127: ACL can be also affected by climate changes and resulting alkane degradation, such as temperature and relative humidity. Terrestrial plants tend to produce longer n-alkanes to protect their water loss under higher temperature and drier conditions. Moreover, higher temperature and wetter conditions may facilitate higher microbial activities, may resulting in the faster degradation of organic matter.
L148: Add “may” before “contain”.
L145-146: Could you show a supplementary figure or table for these correlations?
L227: Please specify what biomolecules or organic indices can give insight into different OM sources.
L240: Change to “higher ACL” and “lower Paq”.
L260: Add a supplementary figure or table for these correlations. And elsewhere.
L280: Higher ACL does not indicate higher terrestrial source. Higher temperature or drier climate can also lead to higher ACL values.
L285: ACL can be affected multiple factors. Please see my comment “L127”.
L308: Are there aquatic plants grow around the study area? Higher Paq ratios could also be due to input of mosses - they also produce lots of mid-chain n-alkanes.
L318 and 330: Again, delete “or bacterial”. Microbial origin contains bacterial origin.
L346: Change to “rivers”.
L357: Add more references (e.g., Evert et al. 2016, https://doi.org/10.1177/0959683616645942; Yao et al., 2021, https://doi.org/10.1130/G48891.1).
L359: Please specify what past environments.
L370: The impacts of findings should be described as well. E.g. why are these findings important and for whom?
Table 2: Add m/z data of molecular weight, base peak, and characteristic peak of each individual compounds.
Loeka Laura Jongejans et al.
Loeka Laura Jongejans et al.
Viewed
| HTML | XML | Total | Supplement | BibTeX | EndNote | |
|---|---|---|---|---|---|---|
| 311 | 70 | 10 | 391 | 26 | 4 | 4 |
- HTML: 311
- PDF: 70
- XML: 10
- Total: 391
- Supplement: 26
- BibTeX: 4
- EndNote: 4
Viewed (geographical distribution)
| Country | # | Views | % |
|---|
| Total: | 0 |
| HTML: | 0 |
| PDF: | 0 |
| XML: | 0 |
- 1