Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)

Author(s) Jahn, A., Lindsay, K., Giraud, X., Gruber, N., Otto-Bliesner, B.L., Liu, Z., Brady, E.C.
Publication Type Journal Items, Publication Status: Published
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Title Carbon isotopes in the ocean model of the Community Earth System Model (CESM1)
Author(s) Jahn, A.
Lindsay, K.
Giraud, X.
Gruber, N.
Otto-Bliesner, B.L.
Liu, Z.
Journal or Series Title Geoscientific Model Development: GMD
Volume Number 8
Issue Number 8
Start Page 2419
End Page 2434
ISSN 1991-959X
1991-9603
Publisher Copernicus
Publication Place Göttingen
Publication Date 2015-08
Abstract 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 C-13 and the radioactive isotope C-14. We implemented the C-14 tracer in two ways: in the "abiotic" case, the C-14 tracer is only subject to air-sea gas exchange, physical transport, and radioactive decay, while in the "biotic" version, the C-14 additionally follows the C-13 tracer through all biogeochemical and ecological processes. Thus, the abiotic C-14 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 C-14 bomb uptake and the C-13 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.
DOI 10.5194/gmd-8-2419-2015
Document Type Article
Publication Status Published
Language English
Assigned Organisational Unit(s) 03731
Organisational Unit(s)
NEBIS System Number 010180250
Source Database ID WOS-000360652200003
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@article{Jhn2015,
author = "Jahn, A. and Lindsay, K. and Giraud, X. and Gruber, N. and Otto-Bliesner, B.L. and Liu, Z. and Brady, E.C.",
title = "{C}arbon isotopes in the ocean model of the {C}ommunity {E}arth {S}ystem {M}odel ({C}{E}{S}{M}1)",
journal = "Geoscientific Model Development: GMD",
year = 2015,
volume = "8",
number = "8",
pages = "2419--2434",
month = aug,
}


E-Citations record created: Mon, 28 Sep 2015, 08:39:43 CET