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| Titel |
GDGT distributions on the East Siberian Arctic Shelf: implications for organic carbon export, burial and degradation |
| VerfasserIn |
R. B. Sparkes, A. Doğrul Selver, J. Bischoff, H. M. Talbot, Ö. Gustafsson, I. P. Semiletov, O. V. Dudarev, B. E. van Dongen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 12 ; Nr. 12, no. 12 (2015-06-18), S.3753-3768 |
| Datensatznummer |
250117992
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| Publikation (Nr.) |
 copernicus.org/bg-12-3753-2015.pdf |
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| Zusammenfassung |
| Siberian permafrost contains a globally significant pool of organic carbon
(OC) that is vulnerable to enhanced warming and subsequent release into the
contemporary carbon cycle. OC release by both fluvial and coastal erosion has
been reported in the region, but the behaviour of this material in the Arctic
Ocean is insufficiently understood. The balance between OC deposition and
degradation on the East Siberian Arctic Shelf (ESAS) influences the
climate–carbon cycle feedback in this area. In this study we couple
measurements of glycerol dialkyl glycerol tetraethers (GDGTs) with bulk
geochemical observations to improve knowledge of the sources of OC to the
ESAS, the behaviour of specific biomarkers on the shelf and the balance
between delivery and removal of different carbon pools. Branched GDGT
(brGDGT) concentrations were highest close to river mouths, yet low in
"ice complex" permafrost deposits, supporting recent observations that brGDGTs
are mostly delivered by fluvial erosion, and may be a tracer for this in
complex sedimentary environments. BrGDGT concentrations and the branched and
isoprenoidal tetraether (BIT) index reduced quickly offshore, demonstrating a
rapid reduction in river influence. Stable carbon isotope ratios changed at a
different rate to the BIT index, suggesting not only that OC on the shelf is
sourced from fluvial erosion but also that erosion of coastal sediments delivers
substantial quantities of OC to the Arctic Ocean. A model of OC export from
fluvial, coastal and marine sources is able to recreate the biomarker and
bulk observations and provide estimates for the influence of fluvial and
coastal OC across the whole shelf. The model shows that coastal erosion
delivers 43 % of the OC and 87 % of the mineral sediment to the ESAS,
but that rivers deliver 72 % of brGDGTs, indicating that brGDGTs can be
used as a proxy for river-derived sediment. |
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