Journal
JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES
Volume 116, Issue -, Pages -Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1029/2011JG001647
Keywords
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Funding
- German Ministry of Science and Education (Russian-German science collaboration Laptev Sea System)
- German Research Foundation (DFG) [SCHI 975/1-2, KI 849]
- NASA [NNX08AJ37G]
- NSF [ARC-0732735, 0747195, 0516326, 0620579]
- Division Of Environmental Biology
- Direct For Biological Sciences [1026415, 0516326, 0620579] Funding Source: National Science Foundation
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Permafrost deposits constitute a large organic carbon pool highly vulnerable to degradation and potential carbon release due to global warming. Permafrost sections along coastal and river bank exposures in NE Siberia were studied for organic matter (OM) characteristics and ice content. OM stored in Quaternary permafrost grew, accumulated, froze, partly decomposed, and refroze under different periglacial environments, reflected in specific biogeochemical and cryolithological features. OM in permafrost is represented by twigs, leaves, peat, grass roots, and plant detritus. The vertical distribution of total organic carbon (TOC) in exposures varies from 0.1 wt % of the dry sediment in fluvial deposits to 45 wt % in Holocene peats. Variations in OM parameters are related to changes in vegetation, bioproductivity, pedogenic processes, decomposition, and sedimentation rates during past climate variations. High TOC, high C/N, and low delta C-13 reflect less decomposed OM accumulated under wet, anaerobic soil conditions characteristic of interglacial and interstadial periods. Glacial and stadial periods are characterized by less variable, low TOC, low C/N, and high delta C-13 values indicating stable environments with reduced bioproductivity and stronger OM decomposition under dryer, aerobic soil conditions. Based on TOC data and updated information on bulk densities, we estimate average organic carbon inventories for ten different stratigraphic units in northeast Siberia, ranging from 7.2 kg C m(-3) for Early Weichselian fluvial deposits, to 33.2 kg C m(-3) for Middle Weichselian Ice Complex deposits, to 74.7 kg C m(-3) for Holocene peaty deposits. The resulting landscape average is likely about 25% lower than previously published permafrost carbon inventories.
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