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Biogeosciences An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/bg-2017-115
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
03 Apr 2017
Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). A final paper in BG is not foreseen.
Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO2 flux induced by mineralization of terrestrial organic carbon
Erik Gustafsson1,2, Christoph Humborg2,3, Göran Björk4, Christian Stranne5,6,7, Leif G. Anderson4, Marc C. Geibel2,3, Carl-Magnus Mörth5,6, Marcus Sundbom3, Igor P. Semiletov8,9,10, Brett F. Thornton5,6, and Bo G. Gustafsson1,2 1Baltic Nest Institute, Stockholm University, Stockholm, 10691, Sweden
2Baltic Sea Centre, Stockholm University, Stockholm, 10691, Sweden
3Department of Environmental Science and Analytical Chemistry, Stockholm University, Stockholm, 10691, Sweden
4Department of Marine Sciences, University of Gothenburg, Gothenburg, 40530, Sweden
5Department of Geological Sciences, Stockholm University, Stockholm, 10691, Sweden
6Bolin Centre for Climate Research, Stockholm University, Stockholm, 10691, Sweden
7Center for Coastal and Ocean Mapping, University of New Hampshire, Durham, 03824, New Hampshire, USA
8University of Alaska Fairbanks, International Arctic Research Center, Fairbanks, Alaska, 99775-7320, USA
9Tomsk Polytechnic University, Tomsk, 634050, Russia
10Russian Academy of Sciences, Pacific Oceanological Institute, Vladivostok, 690041, Russia
Abstract. Measurements from the SWERUS-C3 and ISSS-08 Arctic expeditions were used to calibrate and validate a new physical-biogeochemical model developed to quantify key carbon cycling processes on the East Siberian Arctic Shelf (ESAS). The model was used in a series of experimental simulations with the specific aim to investigate the pathways of terrestrial dissolved and particulate organic carbon (DOCter and POCter) supplied to the shelf. Rivers supply on average 8.5 Tg C yr−1 dissolved inorganic carbon (DIC), and further 8.5 and 1.1 Tg C yr−1 DOCter and POCter respectively. Based on observed and simulated DOC concentrations and stable isotope values (δ13CDOC) in shelf waters, we estimate that only some 20 % of the riverine DOCter is labile. According to our model results, an additional supply of approximately 14 Tg C yr−1 eroded labile POCter is however required to describe the observed stable isotope values of DIC (δ13CDIC). Degradation of riverine DOCter and POCter results in a 1.8 Tg C yr−1 reduction in the uptake of atmospheric CO2, while degradation of eroded POCter results in an additional 10 Tg C yr−1 reduction. Our calculations indicate nevertheless that the ESAS is an overall small net sink for atmospheric CO2 (1.7 Tg C yr−1). The external carbon sources are largely compensated by a net export from the shelf to the Arctic Ocean (31 Tg C yr−1), and to a smaller degree by a permanent burial in the sediments (2.7 Tg C yr−1).

Citation: Gustafsson, E., Humborg, C., Björk, G., Stranne, C., Anderson, L. G., Geibel, M. C., Mörth, C.-M., Sundbom, M., Semiletov, I. P., Thornton, B. F., and Gustafsson, B. G.: Carbon cycling on the East Siberian Arctic Shelf – a change in air-sea CO2 flux induced by mineralization of terrestrial organic carbon, Biogeosciences Discuss., https://doi.org/10.5194/bg-2017-115, 2017.
Erik Gustafsson et al.
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Erik Gustafsson et al.
Erik Gustafsson et al.

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Short summary
In this study we quantify key carbon cycling processes on the East Siberian Arctic Shelf. A specific aim is to determine the pathways of terrestrial organic carbon (OC) supplied by rivers and coastline erosion – and particularly to what extent degradation of terrestrial OC contributes to air-sea CO2 exchange. We estimate that the shelf is a weak CO2 sink, although this sink is considerably reduced mainly by degradation of eroded OC and to a lesser extent by degradation of riverine OC.
In this study we quantify key carbon cycling processes on the East Siberian Arctic Shelf. A...
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