Baltic Nest Institute, Stockholm University, Stockholm, 10691, Sweden
Baltic Sea Centre, Stockholm University, Stockholm, 10691, Sweden
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).
This preprint has been withdrawn.
How to cite. 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. [preprint], https://doi.org/10.5194/bg-2017-115, 2017.
Received: 30 Mar 2017 – Discussion started: 03 Apr 2017
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...