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| Titel |
Sea–air CO2 fluxes in the Southern Ocean for the period 1990-2009 |
| VerfasserIn |
A. Lenton, B. Tilbrook, R. M. Law, D. Bakker, S. C. Doney, N. Gruber, M. Ishii, M. Hoppema, N. S. Lovenduski, R. J. Matear, B. I. McNeil, N. Metzl, S. E. Mikaloff Fletcher, P. M. S. Monteiro, C. Rödenbeck, C. Sweeney, T. Takahashi |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 10, no. 6 ; Nr. 10, no. 6 (2013-06-19), S.4037-4054 |
| Datensatznummer |
250018299
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| Publikation (Nr.) |
 copernicus.org/bg-10-4037-2013.pdf |
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| Zusammenfassung |
| The Southern Ocean (44–75° S) plays a critical role in the global
carbon cycle, yet remains one of the most poorly sampled ocean regions.
Different approaches have been used to estimate sea–air CO2 fluxes in
this region: synthesis of surface ocean observations, ocean biogeochemical
models, and atmospheric and ocean inversions. As part of the RECCAP (REgional
Carbon Cycle Assessment and Processes) project, we combine these different
approaches to quantify and assess the magnitude and variability in Southern
Ocean sea–air CO2 fluxes between 1990–2009. Using all models and
inversions (26), the integrated median annual sea–air CO2 flux of
−0.42 ± 0.07 Pg C yr−1 for the 44–75° S region, is
consistent with the −0.27 ± 0.13 Pg C yr−1 calculated using
surface observations. The circumpolar region south of 58° S has a
small net annual flux (model and inversion median:
−0.04 ± 0.07 Pg C yr−1 and observations:
+0.04 ± 0.02 Pg C yr−1), with most of the net annual flux
located in the 44 to 58° S circumpolar band (model and inversion
median: −0.36 ± 0.09 Pg C yr−1 and observations:
−0.35 ± 0.09 Pg C yr−1). Seasonally, in the
44–58° S region, the median of 5 ocean biogeochemical models
captures the observed sea–air CO2 flux seasonal cycle, while the median
of 11 atmospheric inversions shows little seasonal change in the net flux.
South of 58° S, neither atmospheric inversions nor ocean
biogeochemical models reproduce the phase and amplitude of the observed
seasonal sea–air CO2 flux, particularly in the Austral Winter.
Importantly, no individual atmospheric inversion or ocean biogeochemical
model is capable of reproducing both the observed annual mean uptake and the
observed seasonal cycle. This raises concerns about projecting future changes
in Southern Ocean CO2 fluxes. The median interannual variability from
atmospheric inversions and ocean biogeochemical models is substantial in the
Southern Ocean; up to 25% of the annual mean flux, with 25% of this
interannual variability attributed to the region south of 58° S.
Resolving long-term trends is difficult due to the large interannual
variability and short time frame (1990–2009) of this study; this is
particularly evident from the large spread in trends from inversions and
ocean biogeochemical models. Nevertheless, in the period 1990–2009 ocean
biogeochemical models do show increasing oceanic uptake consistent with the
expected increase of −0.05 Pg C yr−1 decade−1. In contrast,
atmospheric inversions suggest little change in the strength of the CO2
sink broadly consistent with the results of Le Quéré et al. (2007). |
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