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| Titel |
Carbon Isotopes in an Earth System Model |
| VerfasserIn |
M. Cuntz, C. H. Reick, E. Maier-Reimer, M. Heimann, M. Scholze, T. Naegler |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250023269
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| Zusammenfassung |
| We present first calculations of the carbon isotopic composition of carbon dioxide in the
Earth System Model (ESM) COSMOS.
Earth System models consist of coupled models of the ocean, the atmosphere, the land
surface, the biosphere (marine and terrestrial, plants and soils), and the cryosphere (snow and
ice). In COSMOS from the Max Planck Institute for Meteorology, Hamburg, Germany, these
components are the model of the atmospheric circulation ECHAM, the physical ocean model
MPI-OM, the land surface parameterisation JSBACH and the oceanic carbon cycle model
HAMOCC. The ESM COSMOS therefore calculates its own climate and CO2 concentrations
during the diel course with a few degrees resolution, driven only by solar activity and human
perturbations.
The new model version now computes the multiple fractionation processes occurring
during uptake of CO2 from the atmosphere by the terrestrial and marine biosphere. The
model then redistributes the isotopic compositions in the land and ocean biospheres,
including respiration, phenology, fire, land-use change and carbon export. This means that it
includes a full isotopic carbon cycle, in the atmosphere, the ocean and on land. The model
calculates not only the stable carbon isotope signatures but also radiocarbon activities in the
Earth System. It will include in future the radiocarbon perturbation due to nuclear bomb
tests.
We compare first results of the ESM with other global estimates of terrestrial
discrimination. We also compare predicted zonal and seasonal variations of isotope ratios in
atmospheric CO2 with measurements from the GLOBALVIEW flask network.
The stable and radioactive carbon isotopes are excellent tests for the overall model
performance but also for individual model components. For example radiocarbon will be
used to test stratosphere-troposphere exchange, ocean circulation and air-sea gas
exchange.
The isotope-enabled model can be used in future for example to predict carbon isotope
ratios of terrestrial plants, globally. It can track the changes in atmospheric compositions due
to land use changes; for example the conversion of C3 ecosystems to C4 cultivation during
the last century. But it can also track carbon isotope changes observed during the little ice
age, as recorded in ice cores, and attribute them to land and ocean processes, and more
specifically to climate or anthropogenic contributions. |
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