Biological production in the Bellingshausen Sea from oxygen-to-argon ratios and oxygen triple isotopes

Castro Morales, Karel, Cassar, N., Shoosmith, D. R. and Kaiser, J. (2013) Biological production in the Bellingshausen Sea from oxygen-to-argon ratios and oxygen triple isotopes. Biogeosciences, 10 (4). pp. 2273-2291.

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We present estimates of mixed-layer net community oxygen production (N) and gross oxygen production (G) of the Bellingshausen Sea in March and April 2007. N was derived from oxygen-to-argon (O2/Ar) ratios; G was derived using the dual-delta method from triple oxygen isotope measurements. In addition, O2 profiles were collected at 253 CTD stations. N is often approximated by the biological oxygen air–sea exchange flux (Fbio based on the O2/Ar supersaturation, assuming that significant horizontal or vertical fluxes are absent. Here we show that the effect of vertical fluxes alone can account for Fbio values < 0 in large parts of the Bellingshausen Sea towards the end of the productive season, which could otherwise be mistaken to represent net heterotrophy. Thus, improved estimates of mixed-layer N can be derived from the sum of Fbio, Fe (entrainment from the upper thermocline during mixed-layer deepening) and Fv (diapycnal eddy diffusion across the base of the mixed layer). In the winter sea ice zone (WSIZ), the corresponding correction results in a small change of Fbio = (30 ± 17) mmol m-2 d-1 to N = (34 ± 17) mmol m-2 d-1. However, in the permanent open ocean zone (POOZ), the original Fbio value of (-17 ± 10) mmol m-2 d-1 gives a corrected value for N of (-2 ± 18) mmol m-2 d-1. We hypothesize that in the WSIZ, enhanced water column stability due to the release of freshwater and nutrients from sea ice melt may account for the higher N value. These results stress the importance of accounting for physical biases when estimating mixed-layer marine productivity from in situ O2/Ar ratios.

Item Type: Article
Additional Information: © Author(s) 2013. This work is distributed under the Creative Commons Attribution 3.0 License.
Uncontrolled Keywords: sdg 14 - life below water ,/dk/atira/pure/sustainabledevelopmentgoals/life_below_water
Faculty \ School: Faculty of Science > School of Environmental Sciences
Related URLs:
Depositing User: Pure Connector
Date Deposited: 08 Oct 2013 02:00
Last Modified: 01 Oct 2021 01:55
DOI: 10.5194/bg-10-2273-2013

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