Sea-air exchange patterns along the central and outer East Siberian Arctic Shelf as inferred from continuous CO2, stable isotope, and bulk chemistry measurements

• Published in: Global Biogeochemical Cycles
• Main Authors: Humborg, Christoph, Geibel, Marc C., Anderson, Leif G., Björk, Göran, Mörth, Carl-Magnus, Sundbom, Marcus, Thornton, Brett F., Deutsch, Barbara, Gustafsson, Erik, Gustafsson, Bo, Ek, Jörgen, Semiletov, Igor
• Format: Article in Journal/Newspaper
• Language: English
• Published: Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi 2017
• Subjects: Earth and Related Environmental Sciences; Geovetenskap och miljövetenskap; Arctic; Arctic Ocean; East Siberian Sea; Laptev Sea; laptev
• Online Access: http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-147186; https://doi.org/10.1002/2017GB005656

This large-scale quasi-synoptic study gives a comprehensive picture of sea-air CO2 fluxes during the melt season in the central and outer Laptev Sea (LS) and East Siberian Sea (ESS). During a 7 week cruise we compiled a continuous record of both surface water and air CO2 concentrations, in total 76,892 measurements. Overall, the central and outer parts of the ESAS constituted a sink for CO2, and we estimate a median uptake of 9.4 g C m(-2) yr(-1) or 6.6 Tg C yr(-1). Our results suggest that while the ESS and shelf break waters adjacent to the LS and ESS are net autotrophic systems, the LS is a net heterotrophic system. CO2 sea-air fluxes for the LS were 4.7 g C m(-2) yr(-1), and for the ESS we estimate an uptake of 7.2 g C m(-2) yr(-1). Isotopic composition of dissolved inorganic carbon (delta C-13(DIC) and delta C-13(CO2)) in the water column indicates that the LS is depleted in delta C-13(DIC) compared to the Arctic Ocean (ArcO) and ESS with an offset of 0.5% which can be explained by mixing of delta C-13(DIC)-depleted riverine waters and 4.0 Tg yr(-1) respiration of OCter; only a minor part (0.72 Tg yr(-1)) of this respired OCter is exchanged with the atmosphere. Property-mixing diagrams of total organic carbon and isotope ratio (delta C-13(SPE-DOC)) versus dissolved organic carbon (DOC) concentration diagram indicate conservative and nonconservative mixing in the LS and ESS, respectively. We suggest land-derived particulate organic carbon from coastal erosion as an additional significant source for the depleted delta C-13(DIC).