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| Titel |
Sensitivity of different formulations of the seawater CaCO3 saturation state (ΔCO3, Ω ) to ocean acidification: implications for pelagic CaCO3 dissolution in ocean biogeochemical models |
| VerfasserIn |
Birgit Schneider |
| 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 |
250048292
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| Zusammenfassung |
| The saturation state of seawater with respect to CaCO3 can usually be expressed in two
different ways, either as the difference of the in situ carbonate ion concentration to saturation
(ΔCO3=CO3-CO3,sat) or as the ratio (Ω=CO3/CO3,sat). Since both formulations refer to the
same phenomenon, the deviation from equilibrium, they are usually considered as equally
applicable. However, a difference in the pressure (depth) dependent sensitivity of both
expressions to ocean acidification (change in CO3) may result in an underestimation
(overestimation) of the vulnerability of deep (shallow) ocean calcifying organisms when
using Ω. According to a simple sensitivity analysis, the change of Ω at depth has only 1/3
of the effect that would be seen at the sea surface for the same amount of CO3
change. When applied for the calculation of CaCO3 dissolution kinetics, e.g. in ocean
biogeochemical models, this results in a three-times slower CaCO3 dissolution reaction
at depth, although finally the same amount of CaCO3 would be dissolved. This
slow-down may even grow when non-linear dissolution kinetics (higher reaction rate
orders) are applied. In a sensitivity study an ocean biogeochemical model is used,
exploring the parameter space of CaCO3 dissolution kinetics as given in the literature.
Forced by a 1-4xCO2 scenario including stabilization thereafter, we find that the
resulting reduction in CaCO3 export at the millennial time scale varies between
two and more than 10 percent, which means that there are significant differences
in the impact on particle ballasting, depending on the kinetic expression applied. |
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