Journal
BIOGEOSCIENCES
Volume 13, Issue 17, Pages 5003-5019Publisher
COPERNICUS GESELLSCHAFT MBH
DOI: 10.5194/bg-13-5003-2016
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Funding
- Knut and Alice Wallenberg Foundation
- Headquarters of the Far Eastern Branch of the Russian Academy of Sciences
- Swedish Research Council (VR) [621-2004-4039, 621-2007-4631, 621-2013-5297]
- US National Oceanic and Atmospheric Administration (OAR Climate Program Office) [NA08OAR4600758]
- Russian Foundation of Basic Research RFFI [08-05-13572, 08-05-00191-a, 07-05-00050a]
- Swedish Polar Research Secretariat
- US National Science Foundation [OPP ARC 0909546]
- Climate Research School of the Bolin Climate Research Centre
- EU [PIEF-GA-2011-300259, 328049]
- Russian Government [14.Z50.31.0012]
- Russian Science Foundation [15-17-20032]
- Russian Science Foundation [15-17-20032] Funding Source: Russian Science Foundation
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Ongoing global warming in high latitudes may cause an increasing supply of permafrost-derived organic carbon through both river discharge and coastal erosion to the Arctic shelves. Mobilized permafrost carbon can be either buried in sediments, transported to the deep sea or degraded to CO2 and outgassed, potentially constituting a positive feedback to climate change. This study aims to assess the fate of terrigenous organic carbon (TerrOC) in the Arctic marine environment by exploring how it changes in concentration, composition and degradation status across the wide Laptev Sea shelf. We analyzed a suite of terrestrial biomarkers as well as source-diagnostic bulk carbon isotopes (delta C-13, Delta C-14) in surface sediments from a Laptev Sea transect spanning more than 800 km from the Lena River mouth (< 10m water depth) across the shelf to the slope and rise (2000-3000m water depth). These data provide a broad view on different TerrOC pools and their behavior during cross-shelf transport. The concentrations of lignin phenols, cutin acids and high-molecular-weight (HMW) wax lipids (tracers of vascular plants) decrease by 89-99% along the transect. Molecular-based degradation proxies for TerrOC (e.g., the carbon preference index of HMW lipids, the HMW acids / alkanes ratio and the acid / aldehyde ratio of lignin phenols) display a trend to more degraded TerrOC with increasing distance from the coast. We infer that the degree of degradation of permafrost-derived TerrOC is a function of the time spent under oxic conditions during protracted cross-shelf transport. Future work should therefore seek to constrain cross-shelf transport times in order to compute a TerrOC degradation rate and thereby help to quantify potential carbon-climate feedbacks.
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