Molecular and radiocarbon constraints on sources and degradation of terrestrial organic carbon along the Kolyma paleoriver transect, East Siberian Sea

• Published in: Biogeosciences
• Main Authors: Vonk, J. E., Sánchez-García, L., Semiletov, I., Dudarev, O., Eglinton, T.I., Andersson, A., Gustafsson, O.
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2010
• Subjects: /dk/atira/pure/sustainabledevelopmentgoals/climate_action; name=SDG 13 - Climate Action; /dk/atira/pure/sustainabledevelopmentgoals/life_below_water; name=SDG 14 - Life Below Water; Arctic; East Siberian Sea; Kolyma; Ice; kolyma river; permafrost; Siberia
• Online Access: https://research.vu.nl/en/publications/0db6c3cb-946f-4708-a10a-ad1d8fcc1eef; https://doi.org/10.5194/bg-7-3153-2010; https://hdl.handle.net/1871.1/0db6c3cb-946f-4708-a10a-ad1d8fcc1eef; http://www.scopus.com/inward/record.url?scp=77958164459&partnerID=8YFLogxK; http://www.scopus.com/inward/citedby.url?scp=77958164459&partnerID=8YFLogxK

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 (δ 13 C and Δ 14 C) 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 ∼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 (Δ14C ca. -60% or ca. 500 14 C years) terrestrial OC pool in surface water particulate matter, underlain by a less degraded but old (Δ14C ca. -500% or ca. 5500 14 C years) terrestrial OC pool in bottom sediments. We suggest that the terrestrial OC fraction in surface water particulate matter is mainly ...