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| Titel |
Evaluating the deep-ocean circulation of a global ocean model using carbon isotopic ratios |
| VerfasserIn |
Andre Paul, Stephanie Dutkiewicz, Jake Gebbie, Martin Losch, Olivier Marchal |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250132154
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| Publikation (Nr.) |
 EGU/EGU2016-12634.pdf |
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| Zusammenfassung |
| We study the sensitivity of a global three-dimensional biotic ocean carbon-cycle model to the
parameterizations of gas exchange and biological productivity as well as to deep-ocean
circulation strength, and we employ the carbon isotopic ratios δ13C and Δ14C of dissolved
inorganic carbon for a systematic evaluation against observations. Radiocarbon (Δ14C) in
particular offers the means to assess the model skill on a time scale of 100 to 1000 years
relevant to the deep-ocean circulation.
The carbon isotope ratios are included as tracers in the MIT general circulation model
(MITgcm). The implementation involves the fractionation processes during photosynthesis
and air-sea gas exchange. We present the results of sixteen simulations combining two
different parameterizations of the piston velocity, two different parameterizations of
biological productivity (including the effect of iron fertilization) and four different
overturning rates. These simulations were first spun up to equilibrium (more than 10,000
years of model simulation) and then continued from AD 1765 to AD 2002. For the model
evaluation, we followed the OCMIP-2 (Ocean Carbon-Cycle Model Intercomparision Project
phase two) protocol, comparing the results to GEOSECS (Geochemical Ocean Sections
Survey) and WOCE (World Ocean Circulation Experiment) δ13C and natural Δ14C data in
the world ocean.
The range of deep natural Δ14C (below 1000 m) for our single model (MITgcm) was
smaller than for the group of different OCMIP-2 models. Furthermore, differences
between different model parameterizations were smaller than for different overturning
rates.
We conclude that carbon isotope ratios are a useful tool to evaluate the deep-ocean
circulation. Since they are also available from deep-sea sediment records, we postulate that
the simulation of carbon isotope ratios in a global ocean model will aid in estimating the
deep-ocean circulation and climate during present and past. |
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