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| Titel |
Interannual-to-decadal variability of North Atlantic air-sea CO2 fluxes |
| VerfasserIn |
S. Raynaud, J. C. Orr, O. Aumont, K. B. Rodgers, P. Yiou |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1812-0784
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| Digitales Dokument |
URL |
| Erschienen |
In: Ocean Science ; 2, no. 1 ; Nr. 2, no. 1 (2006-07-17), S.43-60 |
| Datensatznummer |
250000405
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| Publikation (Nr.) |
 copernicus.org/os-2-43-2006.pdf |
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| Zusammenfassung |
| The magnitude of the interannual variability of North Atlantic air-sea
CO2 fluxes remains uncertain. Interannual extremes simulated by
atmospheric inverse approaches are typically about ±0.3 Pg C yr−1,
whereas those from ocean models are less than ±0.1 Pg C yr−1. Thus
variability in the North Atlantic is either about 60% or less than
20% of the global variability of about ±0.5 Pg C yr−1 (as estimated
by both approaches). Here we explore spatiotemporal variability within
the North Atlantic basin of one ocean model in order to more fully
describe potential counteracting trends in different regions that may
explain why basin-wide variability is small relative to global-scale
variability. Typical atmospheric inverse approaches separate the North
Atlantic into at most a few regions and thus cannot properly simulate
such counteracting effects. For this study, two simulations were made
with a biogeochemical model coupled to a global ocean general
circulation model (OGCM), which itself was forced by 55-year NCEP
reanalysis fields. In the first simulation, atmospheric CO2 was
maintained at the preindustrial level (278 ppmv); in the second
simulation, atmospheric CO2 followed the observed increase.
Simulated air-sea CO2 fluxes and associated variables were then
analysed with a statistical tool known as multichannel singular
spectrum analysis (MSSA). We found that the subtropical gyre is not
the largest contributor to the overall, basin-wide variability, in
contrast to previous suggestions. The subpolar gyre and the
inter-gyre region (the transition area between subpolar and
subtropical gyres) also contribute with multipolar anomalies at
multiple frequencies: these tend to cancel one another in terms of the
basin-wide air-sea CO2 flux. We found a strong correlation between
the air-sea CO2 fluxes and the North Atlantic Oscillation (NAO), but
only if one takes into account time lags as does MSSA (maximum
r=0.64 for lags between 1 and 3 years). The effect of increasing
atmospheric CO2 (the anthropogenic perturbation) on total variability
was negligible at interannual time scales, whereas at the decadal
(13-year) time scale, it increased variability by 30%. |
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