Fate of terrigenous organic matter across the Laptev Sea from the mouth of the Lena River to the deep sea of the Arctic interior
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 CO<sub>...
| Main Authors: | , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-09-01
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| Series: | Biogeosciences |
| Online Access: | http://www.biogeosciences.net/13/5003/2016/bg-13-5003-2016.pdf |
| Summary: | 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 CO<sub>2</sub> and
outgassed, potentially constituting a positive feedback to climate change.
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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 (<i>δ</i><sup>13</sup>C, Δ<sup>14</sup>C) in surface sediments from a
Laptev Sea transect spanning more than 800 km from the Lena River mouth
(< 10 m water depth) across the shelf to the slope and rise
(2000–3000 m 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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| ISSN: | 1726-4170 1726-4189 |