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| Titel |
Carbon transport by the Lena River from its headwaters to the Arctic Ocean, with emphasis on fluvial input of terrestrial particulate organic carbon vs. carbon transport by coastal erosion |
| VerfasserIn |
I. P. Semiletov, I. I. Pipko, N. E. Shakhova, O. V. Dudarev, S. P. Pugach, A. N. Charkin, C. P. McRoy, D. Kosmach, Ö. Gustafsson |
| 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 ; 8, no. 9 ; Nr. 8, no. 9 (2011-09-02), S.2407-2426 |
| Datensatznummer |
250006110
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| Publikation (Nr.) |
 copernicus.org/bg-8-2407-2011.pdf |
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| Zusammenfassung |
| The Lena River integrates biogeochemical signals from its vast drainage
basin, and the integrated signal reaches far out over the Arctic Ocean.
Transformation of riverine organic carbon (OC) into mineral carbon, and
mineral carbon into the organic form in the Lena River watershed, can be
considered to be quasi-steady-state processes. An increase in Lena discharge
exerts opposite effects on total organic (TOC) and total inorganic
(TCO2) carbon: TOC concentration increases, while TCO2
concentration decreases. Significant inter-annual variability in mean values
of TCO2, TOC, and their sum (total carbon, TC) has been found. This
variability is determined by changes in land hydrology which cause
differences in the Lena River discharge. There is a negative correlation in
the Lena River between TC in September and its mean discharge in August; a
time shift of about one month is required for water to travel from Yakutsk
to the Laptev Sea. Total carbon entering the sea with the Lena discharge is
estimated to be almost 10 Tg C yr−1. The annual Lena River discharge of
particulate organic carbon (POC) can be as high as 0.38 Tg (moderate to high
estimate). If we instead accept Lisytsin's (1994) statement that 85–95 %
of total particulate matter (PM) (and POC) precipitates on the marginal
"filter", then only about 0.03–0.04 Tg of Lena River POC reaches the
Laptev Sea. The Lena's POC export would then be two orders of magnitude less
than the annual input of eroded terrestrial carbon onto the shelf of the
Laptev and East Siberian seas, which is estimated to be about 4 Tg.
Observations support the hypothesis of a dominant role for coastal erosion
(Semiletov, 1999a, b) in East Siberian Arctic Shelf (ESAS) sedimentation and
the dynamics of the carbon/carbonate system. The Lena River is characterized
by relatively high concentrations of the primary greenhouse gases, dissolved
carbon dioxide (CO2) and methane (CH4). During all seasons the
river is supersaturated in CO2 compared to the atmosphere, by up to
1.5–2 fold in summer, and 4–5 fold in winter. This results in a significant
CO2 supersaturation in the adjacent coastal sea. Localized areas of
dissolved CH4 along the Lena River and in the Lena delta channels may
reach 100 nM, but the CH4 concentration decreases to 5–20 nM towards
the sea, which suggests that riverborne export of CH4 plays but a minor
role in determining the ESAS CH4 budget in coastal waters. Instead, the
seabed appears to be the source that provides most of the CH4 to the
Arctic Ocean. |
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