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. Gustafsson1,21Baltic 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
Received: 30 Mar 2017 – Accepted for review: 03 Apr 2017 – Discussion started: 03 Apr 2017
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).
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., doi:10.5194/bg-2017-115, in review, 2017.