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| Titel |
Carbon isotopes in the ocean model of the Community Earth System Model (CESM1) |
| VerfasserIn |
A. Jahn, K. Lindsay, X. Giraud, N. Gruber, B. L. Otto-Bliesner, Z. Liu, E. C. Brady |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 8 ; Nr. 8, no. 8 (2015-08-05), S.2419-2434 |
| Datensatznummer |
250116500
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| Publikation (Nr.) |
 copernicus.org/gmd-8-2419-2015.pdf |
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| Zusammenfassung |
| Carbon isotopes in the ocean are frequently used as paleoclimate proxies and as present-day
geochemical ocean tracers. In order to allow a more direct comparison of climate model results
with this large and currently underutilized data set, we added a carbon isotope module to the ocean
model of the Community Earth System Model (CESM), containing the cycling of the stable isotope
13C and the radioactive isotope 14C. We implemented the 14C tracer
in two ways: in the "abiotic" case, the 14C tracer is only subject to air–sea gas
exchange, physical transport, and radioactive decay, while in the "biotic" version, the
14C additionally follows the 13C tracer through all biogeochemical and
ecological processes. Thus, the abiotic 14C tracer can be run without the ecosystem
module, requiring significantly fewer computational resources. The carbon isotope module calculates
the carbon isotopic fractionation during gas exchange, photosynthesis, and calcium carbonate
formation, while any subsequent biological process such as remineralization as well as any
external inputs are assumed to occur without fractionation. Given the uncertainty associated with
the biological fractionation during photosynthesis, we implemented and tested three
parameterizations of different complexity. Compared to present-day observations, the model is able
to simulate the oceanic 14C bomb uptake and the 13C Suess effect reasonably
well compared to observations and other model studies. At the same time, the carbon isotopes reveal
biases in the physical model, for example, too sluggish ventilation of the deep Pacific Ocean. |
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