the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
the Creative Commons Attribution-NonCommercial-ShareAlike 2.5 License.
The role of N2-fixation to simulate the pCO2 observations from the Baltic Sea
Abstract. Measurements in the central Baltic Sea have shown that dissolved inorganic carbon (DIC) concentrations in the upper water column continue to decrease even after complete depletion of dissolved inorganic nitrogen (DIN). To explain this observation, a new external supply of nitrogen is required without a concomitant supply of inorganic carbon. The primary proposed candidate process is N2-fixation. In order to address this question in the eastern Gotland Sea, a biogeochemical model containing nine state variables including diatoms, flagellates, and nitrogen fixing cyanobacteria, was coupled to a 1D physical model. The results from the winter period until the onset of the spring bloom of 1997 gave reasonable surface water values for partial pressure of CO2 (pCO2) compared with measurements of the pCO2. However, the model failed to simulate the observed pCO2 drawdown for the period from the end of the spring bloom until late summer. Even after introducing a seasonal dissolved organic carbon (DOC) excess production and varying different process parameterization the simulated pCO2 values did not improve. Only the shift from a sharp to a moderate temperature dependency in addition to an increase in the C:P ratio of the nitrogen fixing cyanobacteria made it possible for the model to match the pCO2 observations. The resulting total nitrogen fixation (167 mmol m-2 a-1) exceeds previous measurement-based estimates but is in good agreement with recent rate measurement based estimates.
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RC S271: 'The role of N2-fixation to simulate the', Anonymous Referee #1, 17 Jun 2005
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RC S367: 'General Comments', Anonymous Referee #2, 22 Jul 2005
- AC S456: 'Addressing comments of referee #2', Anita Leinweber, 20 Aug 2005
- AC S449: 'Addressing comments of referee #1', Anita Leinweber, 20 Aug 2005
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RC S367: 'General Comments', Anonymous Referee #2, 22 Jul 2005
-
RC S271: 'The role of N2-fixation to simulate the', Anonymous Referee #1, 17 Jun 2005
-
RC S367: 'General Comments', Anonymous Referee #2, 22 Jul 2005
- AC S456: 'Addressing comments of referee #2', Anita Leinweber, 20 Aug 2005
- AC S449: 'Addressing comments of referee #1', Anita Leinweber, 20 Aug 2005
-
RC S367: 'General Comments', Anonymous Referee #2, 22 Jul 2005
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Cited
4 citations as recorded by crossref.
- Carbon dioxide in European coastal waters A. Borges et al. 10.1016/j.ecss.2006.05.046
- Modelling the uptake and release of carbon dioxide in the Baltic Sea surface water A. Omstedt et al. 10.1016/j.csr.2009.01.006
- Carbon cycling in the Baltic Sea — The fate of allochthonous organic carbon and its impact on air–sea CO2 exchange E. Gustafsson et al. 10.1016/j.jmarsys.2013.07.005
- Biogeochemical Control of the Coupled CO2–O2 System of the Baltic Sea: A Review of the Results of Baltic-C A. Omstedt et al. 10.1007/s13280-013-0485-4