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| Titel |
Carbon dynamics and CO2 air-sea exchanges in the eutrophied coastal waters of the Southern Bight of the North Sea: a modelling study |
| VerfasserIn |
N. Gypens, C. Lancelot, A. V. Borges |
| 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 ; 1, no. 2 ; Nr. 1, no. 2 (2004-12-23), S.147-157 |
| Datensatznummer |
250000139
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| Publikation (Nr.) |
 copernicus.org/bg-1-147-2004.pdf |
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| Zusammenfassung |
| A description of the carbonate system has been incorporated in the MIRO
biogeochemical model to investigate the contribution of diatom and
Phaeocystis blooms to the seasonal dynamics of air-sea CO2 exchanges in the
Eastern Channel and Southern Bight of the North Sea, with focus on the
eutrophied Belgian coastal waters. For this application, the model was
implemented in a simplified three-box representation of the hydrodynamics
with the open ocean boundary box ‘Western English Channel’ (WCH) and the
‘French Coastal Zone’ (FCZ) and ‘Belgian Coastal Zone’ (BCZ) boxes receiving
carbon and nutrients from the rivers Seine and Scheldt, respectively.
Results were obtained by running the model for the 1996–1999 period. The
simulated partial pressures of CO2 (pCO2) were successfully
compared with data recorded over the same period in the central BCZ at
station 330 (51°26.05′ N; 002°48.50′ E). Budget calculations based
on model simulations of carbon flow rates indicated for BCZ a low annual
sink of atmospheric CO2 (−0.17 mol C m-2 y-1). On the
opposite, surface water pCO2 in WCH was estimated to be at annual
equilibrium with respect to atmospheric CO2. The relative contribution
of biological, chemical and physical processes to the modelled seasonal
variability of pCO2 in BCZ was further explored by running model
scenarios with separate closures of biological activities and/or river
inputs of carbon. The suppression of biological processes reversed direction
of the CO2 flux in BCZ that became, on an annual scale, a significant
source for atmospheric CO2 (+0.53 mol C m-2 y-1). Overall
biological activity had a stronger influence on the modelled seasonal cycle
of pCO2 than temperature. Especially Phaeocystis colonies which growth in spring
were associated with an important sink of atmospheric CO2 that
counteracted the temperature-driven increase of pCO2 at this period of
the year. However, river inputs of organic and inorganic carbon were shown
to increase the surface water pCO2 and hence the emission of CO2 to the atmosphere. Same calculations conducted in WCH, showed that
temperature was the main factor controlling the seasonal pCO2 cycle in
these open ocean waters. The effect of interannual variations of fresh water
discharge (and related nutrient and carbon inputs), temperature and wind
speed was further explored by running scenarios with forcing typical of two
contrasted years (1996 and 1999). Based on these simulations, the model
predicts significant variations in the intensity and direction of the annual
air-sea CO2 flux. |
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