Interannual-to-decadal variability of North Atlantic air-sea CO 2 fluxes
PAR00002831 International audience The magnitude of the interannual variability of North Atlantic air-sea CO 2 fluxes remains uncertain. Fluxes inferred from atmospheric inversions have large variability, whereas those simulated by ocean models have small variability. Part of the difference is that...
Published in: | Ocean Science |
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Main Authors: | , , , , |
Other Authors: | , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2005
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Subjects: | |
Online Access: | https://hal.science/hal-00331127 https://hal.science/hal-00331127/document https://hal.science/hal-00331127/file/osd-2-437-2005.pdf https://doi.org/10.5194/os-2-43-2006 |
Summary: | PAR00002831 International audience The magnitude of the interannual variability of North Atlantic air-sea CO 2 fluxes remains uncertain. Fluxes inferred from atmospheric inversions have large variability, whereas those simulated by ocean models have small variability. Part of the difference is that unlike typical atmospheric inversions, ocean models come with spatial resolution at the sub-basin scale. Here we explore sub-basin-scale spatiotemporal variability in the North Atlantic in one ocean model in order to better understand why the the North Atlantic basin may well contribute very little to the global variability of air-sea CO 2 flux. We made two simulations 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 CO 2 was maintained at the preindustrial level (278 ppmv); in the second simulation, atmospheric CO 2 followed the observed increase. Simulated air-sea CO 2 fluxes and associated variables were 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 CO 2 flux. We found a strong correlation between the air-sea CO 2 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 contribution of anthropogenic CO 2 to 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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