Release of pre-aged terrestrial organic matter from the Amur watershed during deglacial permafrost thaw revealed by compound-specific 14C analysis


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Gesine.Mollenhauer [ at ] awi.de

Abstract

During the last glacial permafrost-affected areas extended further south and were much larger than at present. During the transition to the Holocene, some of this permafrost must have thawed releasing much of the carbon stored within the soils. This may have contributed to atmospheric pCO2 rise and ∆14C decline, assuming that pre-aged or ancient carbon was released. Thawing permafrost likely has resulted in large amounts of terrigenous organic matter exported to the ocean, and records of this release may be found in sediments accumulated near the mouth of rivers draining permafrost-affected areas. We investigated two sediment cores (LV28-4 and SO178-13-6) recovered from the Okhotsk Sea near the mouth of the Amur River. Biomarker records document increased discharge of terrigenous organic matter during the last deglaciation between 17 and 8 ka. Compound-specific radiocarbon dating of long-chain n-alkanoic acids reveals that the terrigenous organic matter was substantially older at deposition during this period than during the late Holocene. During the deglaciation, ∆14C of these leax-wax lipids was similar to values observed off Siberian rivers draining discontinuous permafrost areas today (i.e., Ob and Yenisei), while modern values compare favourably with leaf-wax ∆14C observed in sediments off the Danube, a large river at a similar latitude as the Amur River. Our records thus provide evidence for deglacial release of substantial amounts of pre-aged organic matter from thawing permafrost.



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Conference (Talk)
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Not peer-reviewed
Publication Status
Published
Event Details
Goldschmidt Conference, 16 Aug 2015 - 21 Aug 2015, Prague.
Eprint ID
39510
Cite as
Mollenhauer, G. , Dummann, W. , Winterfeld, M. , Hefter, J. , Lembke-Jene, L. and Tiedemann, R. (2015): Release of pre-aged terrestrial organic matter from the Amur watershed during deglacial permafrost thaw revealed by compound-specific 14C analysis , Goldschmidt Conference, Prague, 16 August 2015 - 21 August 2015 .


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