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| Titel |
Sea–air CO2 fluxes in the Indian Ocean between 1990 and 2009 |
| VerfasserIn |
V. V. S. S. Sarma, A. Lenton, R. M. Law, N. Metzl, P. K. Patra, S. Doney, I. D. Lima, E. Dlugokencky, M. Ramonet, V. Valsala |
| 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. 11 ; Nr. 10, no. 11 (2013-11-06), S.7035-7052 |
| Datensatznummer |
250085398
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| Publikation (Nr.) |
 copernicus.org/bg-10-7035-2013.pdf |
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| Zusammenfassung |
| The Indian Ocean (44° S–30° N) plays an important role
in the global carbon cycle, yet it remains one of the most poorly sampled ocean
regions. Several approaches have been used to estimate net sea–air CO2
fluxes in this region: interpolated observations, ocean biogeochemical
models, 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 Indian
Ocean sea–air CO2 fluxes between 1990 and 2009. Using all of the models
and inversions, the median annual mean sea–air CO2 uptake of
−0.37 ± 0.06 PgC yr−1 is consistent with the −0.24 ± 0.12 PgC yr−1
calculated from observations. The fluxes from the southern
Indian Ocean (18–44° S; −0.43 ± 0.07 PgC yr−1 are similar in magnitude to the annual uptake
for the entire Indian Ocean. All models capture the observed pattern of
fluxes in the Indian Ocean with the following exceptions: underestimation of
upwelling fluxes in the northwestern region (off Oman and Somalia),
overestimation in the northeastern region (Bay of Bengal) and underestimation of
the CO2 sink in the subtropical convergence zone. These differences
were mainly driven by lack of atmospheric CO2 data in atmospheric
inversions, and poor simulation of monsoonal currents and freshwater
discharge in ocean biogeochemical models. Overall, the models and inversions
do capture the phase of the observed seasonality for the entire Indian Ocean
but overestimate the magnitude. The predicted sea–air CO2 fluxes by
ocean biogeochemical models (OBGMs) respond to seasonal variability with
strong phase lags with reference to climatological CO2 flux, whereas the
atmospheric inversions predicted an order of magnitude higher seasonal flux
than OBGMs. The simulated interannual variability by the OBGMs is weaker
than that found by atmospheric inversions. Prediction of such weak
interannual variability in CO2 fluxes by atmospheric inversions was
mainly caused by a lack of atmospheric data in the Indian Ocean. The OBGM
models suggest a small strengthening of the sink over the period 1990–2009
of −0.01 PgC decade−1. This is inconsistent with the observations in the
southwestern Indian Ocean that shows the growth rate of oceanic pCO2 was
faster than the observed atmospheric CO2 growth, a finding attributed
to the trend of the Southern Annular Mode (SAM) during the 1990s. |
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