Universität zu Köln

Melchert, Jan Olaf ORCID: 0000-0002-1548-340X, Wischhoefer, Philipp, Knoblauch, Christian, Eckhardt, Tim, Liebner, Susanne ORCID: 0000-0002-9389-7093 and Rethemeyer, Janet (2022). Sources of CO2 Produced in Freshly Thawed Pleistocene-Age Yedoma Permafrost. Front. Earth Sci., 9. LAUSANNE: FRONTIERS MEDIA SA. ISSN 2296-6463

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Abstract

The release of greenhouse gases from the large organic carbon stock in permafrost deposits in the circumarctic regions may accelerate global warming upon thaw. The extent of this positive climate feedback is thought to be largely controlled by the microbial degradability of the organic matter preserved in these sediments. In addition, weathering and oxidation processes may release inorganic carbon preserved in permafrost sediments as CO2, which is generally not accounted for. We used C-13 and C-14 analysis and isotopic mass balances to differentiate and quantify organic and inorganic carbon released as CO2 in the field from an active retrogressive thaw slump of Pleistocene-age Yedoma and during a 1.5-years incubation experiment. The results reveal that the dominant source of the CO2 released from freshly thawed Yedoma exposed as thaw mound is Pleistocene-age organic matter (48-80%) and to a lesser extent modern organic substrate (3-34%). A significant portion of the CO2 originated from inorganic carbon in the Yedoma (17-26%). The mixing of young, active layer material with Yedoma at a site on the slump floor led to the preferential mineralization of this young organic carbon source. Admixtures of younger organic substrates in the Yedoma thaw mound were small and thus rapidly consumed as shown by lower contributions to the CO2 produced during few weeks of aerobic incubation at 4 degrees C corresponding to approximately one thaw season. Future CO2 fluxes from the freshly thawed Yedoma will contain higher proportions of ancient inorganic (22%) and organic carbon (61-78%) as suggested by the results at the end, after 1.5 years of incubation. The increasing contribution of inorganic carbon during the incubation is favored by the accumulation of organic acids from microbial organic matter degradation resulting in lower pH values and, in consequence, in inorganic carbon dissolution. Because part of the inorganic carbon pool is assumed to be of pedogenic origin, these emissions would ultimately not alter carbon budgets. The results of this study highlight the preferential degradation of younger organic substrates in freshly thawed Yedoma, if available, and a substantial release of CO2 from inorganic sources.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Melchert, Jan Olaf UNSPECIFIED orcid.org/0000-0002-1548-340X UNSPECIFIED Wischhoefer, Philipp UNSPECIFIED UNSPECIFIED UNSPECIFIED Knoblauch, Christian UNSPECIFIED UNSPECIFIED UNSPECIFIED Eckhardt, Tim UNSPECIFIED UNSPECIFIED UNSPECIFIED Liebner, Susanne UNSPECIFIED orcid.org/0000-0002-9389-7093 UNSPECIFIED Rethemeyer, Janet UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-680882
DOI:	10.3389/feart.2021.737237
Journal or Publication Title:	Front. Earth Sci.
Volume:	9
Date:	2022
Publisher:	FRONTIERS MEDIA SA
Place of Publication:	LAUSANNE
ISSN:	2296-6463
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language SOIL ORGANIC-MATTER; ICE-RICH PERMAFROST; LENA RIVER DELTA; CARBON RELEASE; CLIMATE-CHANGE; GAS-PRODUCTION; DEPOSITS; DYNAMICS; DIOXIDE; VULNERABILITY Multiple languages Geosciences, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/68088