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| Titel |
Modelling coccolithophores in the North Sea: Their impact on the carbon budget |
| VerfasserIn |
Ina Lorkowski, Johannes Pätsch, Fabian Schwichtenberg |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250048349
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| Zusammenfassung |
| Coccolithophores play an important role in the global marine carbon cycle. They affect the
biological pump via primary production and are the most important pelagic calcifiers that
contribute to the carbonate counter pump. Their calcification influences the Total Alkalinity
and DIC concentration of marine ecosystems and thus the pCO2 of seawater and uptake
capacity of atmospheric CO2. While calcification is increasing the pCO2 the primary
production and other mechanisms like enhanced vertical export due to combined calcite
-organic carbon - agglutination is decreasing pCO2. To obtain a reasonable carbon budget
it has to be determined which effect matters most under different environmental
conditions.
Therefore, a coccolithophore module was implemented in the biogeochemical ecosystem
model ECOHAM. The implemented calcification was made dependent on light, temperature
and the calcite saturation state of seawater (Ω). The model consists of three phytoplankton
groups, namely diatoms, coccolithophores and flagellates, two zooplankton groups, bacteria,
two detritus fractions, DOM and inorganic nutrients. It resolves the biogeochemical cycles of
carbon, nitrogen, phosphorus, silicate and oxygen. To capture the effect of calcification
on the carbonate system, Total Alkalinity is computed prognostically. The model
was coupled to HAMSOM for the hydrodynamic calculations and applied to the
North European Continental Shelf (47Ë 41‘ – 63Ë 53’ N, 15Ë 5’ W – 13Ë 55’
E).
The focus of our investigations is lying on the carbon budget and especially the air-sea
flux of carbon dioxide of the North Sea. Blooms of coccolithophores mainly occur in the
deeper and seasonally stratified northern North Sea. This region is characterised as a strong
sink for atmospheric carbon dioxide with a mean uptake of 2.12 mol C yr-1m-2 during 1970
to 2006 in a former ECOHAM simulation without coccolithophores. The comparison of these
results with the corresponding application including the new coccolithophore – module
reveals the effects of calcification on the carbonate system, which occur in the range of
hours and days, and on the annual carbon budgets. When TEP-building processes
including clustering of carbonate and organic carbon are included into the model we see
also a significant change in the strength of the carbon pump on longer time scales. |
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