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Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect, East Siberian Sea
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2010 (English)In: Biogeosciences, ISSN 1726-4170, E-ISSN 1726-4189, Vol. 7Article in journal (Refereed) Published
Abstract [en]

Climate warming in northeastern Siberia may induce thaw-mobilization of the organic carbon (OC) now held in permafrost. This study investigated the composition of terrestrial OC exported to Arctic coastal waters to both obtain a natural integration of terrestrial permafrost OC release and to further understand the fate of released carbon in the extensive Siberian Shelf Seas. Application of a variety of elemental, molecular and isotopic (delta C-13 and Delta C-14) analyses of both surface water suspended particulate matter and underlying surface sediments along a 500 km transect from Kolyma River mouth to the mid-shelf of the East Siberian Sea yielded information on the sources, degradation status and transport processes of thaw-mobilized soil OC. A three end-member dual-carbon-isotopic mixing model was applied to deduce the relative contributions from riverine, coastal erosion and marine sources. The mixing model was solved numerically using Monte Carlo simulations to obtain a fair representation of the uncertainties of both end-member composition and the end results. Riverine OC contributions to sediment OC decrease with increasing distance offshore (35 +/- 15 to 13 +/- 9%), whereas coastal erosion OC exhibits a constantly high contribution (51 +/- 11 to 60 +/- 12%) and marine OC increases offshore (9 +/- 7 to 36 +/- 10%). We attribute the remarkably strong imprint of OC from coastal erosion, extending up to similar to 500 km from the coast, to efficient offshoreward transport in these shallow waters presumably through both the benthic boundary layer and ice-rafting. There are also indications of simultaneous selective preservation of erosion OC compared to riverine OC. Molecular degradation proxies and radiocarbon contents indicated a degraded but young (Delta C-14 ca. -60% or ca. 500 C-14 years) terrestrial OC pool in surface water particulate matter, underlain by a less degraded but old (Delta C-14 ca. -500% or ca. 5500 C-14 years) terrestrial OC pool in bottom sediments. We suggest that the terrestrial OC fraction in surface water particulate matter is mainly derived from surface soil and recent vegetation fluvially released as buoyant organic-rich aggregates (e. g., humics), which are subjected to extensive processing during coastal transport. In contrast, terrestrial OC in the underlying sediments is postulated to originate predominantly from erosion of mineral-rich Pleistocene coasts (i.e., yedoma) and inland mineral soils. Sorptive association of this organic matter with mineral particles protects the OC from remineralization and also promotes rapid settling (ballasting) of the OC. Our findings corroborate recent studies by indicating that different Arctic surface soil OC pools exhibit distinguishing susceptibilities to degradation in coastal waters. Consequently, the general postulation of a positive feedback to global warming from degradation of permafrost carbon may be both attenuated (by reburial of one portion) and geographically displaced (degradation of released terrestrial permafrost OC far out over the Arctic shelf seas).

Place, publisher, year, edition, pages
2010. Vol. 7
Keyword [en]
arctic shelf waters bay mixing zone marine-sediments climate-change permafrost ocean matter coastal cycle river Environmental Sciences & Ecology Geology
Research subject
SWEDARCTIC 2008, ISSS-08
Identifiers
URN: urn:nbn:se:polar:diva-1939DOI: 10.5194/bg-7-3153-2010OAI: oai:DiVA.org:polar-1939DiVA: diva2:810352
Note

ISI Document Delivery No.: 673KM Times Cited: 30 Cited Reference Count: 79 Vonk, J. E. Sanchez-Garcia, L. Semiletov, I. Dudarev, O. Eglinton, T. Andersson, A. Gustafsson, O. Vonk, Jorien/H-5422-2011; Semiletov, Igor/B-3616-2013; Sanchez-Garcia, Laura/N-1172-2013 Sanchez-Garcia, Laura/0000-0002-7444-1242 Knut and Alice Wallenberg Foundation, Headquarters of the Far Eastern Branch of the Russian Academy of Sciences; Swedish Research Council [621-2004-4039, 621-2007-4631]; US National Oceanic and Atmospheric Administration; Russian Foundation of Basic Research [08-05-13572, 08-05-00191-a, 07-05-00050a]; Swedish Polar Research Secretariat; Nordic Council of Ministers [331080-70219]; National Science Foundation [OPP ARC 0909546]; Swedish Royal Academy of Sciences; Marie Curie grant [PIEF-GA-2008-220424]; NSF [ARC-0909377]; Knut and Alice Wallenberg Foundation We wish to thank many colleagues of the International Siberian Shelf Study 2008 (ISSS-08): Martin Krusa and Bart van Dongen for massive numbers of high-volume GF/F filtrations, Goran Bjork for the salinity and depth data, Vladimir Mordukhovich for help with sediment sampling and many other colleagues onboard the ISSS-08 expedition for laboratory and field assistance. The ISSS-08 program was supported by the Knut and Alice Wallenberg Foundation, Headquarters of the Far Eastern Branch of the Russian Academy of Sciences, the Swedish Research Council (VR Contract No. 621-2004-4039 and 621-2007-4631), the US National Oceanic and Atmospheric Administration (Siberian Shelf Study), the Russian Foundation of Basic Research (08-05-13572, 08-05-00191-a, and 07-05-00050a), the Swedish Polar Research Secretariat, the Arctic Co-Op Program of the Nordic Council of Ministers (331080-70219) and the National Science Foundation (OPP ARC 0909546). O. G. also acknowledges financial support as an Academy Research Fellow from the Swedish Royal Academy of Sciences, L. S. a Marie Curie grant (contract no. PIEF-GA-2008-220424), T. E. an NSF grant (ARC-0909377) and A. A. support from the Knut and Alice Wallenberg Foundation. 30 Copernicus gesellschaft mbh Gottingen Ecology; Geosciences, Multidisciplinary

Available from: 2015-05-07 Created: 2015-05-06 Last updated: 2015-05-26

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