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| Titel |
A model-based evaluation of the transit-time distribution (TTD) method for inferring anthropogenic carbon storage in the ocean |
| VerfasserIn |
Yan-Chun He, Jerry Tjiputra, Helene Langehaug, Emil Jeansson, Yongqi Gao, Jörg Schwinger, Are Olsen |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250146221
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| Publikation (Nr.) |
 EGU/EGU2017-10232.pdf |
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| Zusammenfassung |
| The transit time distribution (TTD) method is widely used to infer the anthropogenic carbon
(Cant) concentration in the ocean with obtained water mass age from transient tracers such as
chlorofluorocarbons (CFCs) and sulfur hexafluoride (SF6). Its accuracy relies on the
validity of several assumptions, notably (i) a steady state ocean circulation, (ii) a
prescribed tracer saturation history, e.g., a constant 100% saturation, (iii) a prescribed
degree of mixing in the ocean, denoted as Δ∕Γ, e.g., a unity Δ∕Γ in space and
time, (iv) a constant surface water air-sea CO2 disequilibrium with time, and (v)
that preformed alkalinity can be sufficiently estimated by salinity or salinity and
temperature. Here, these assumptions are evaluated using model-simulated data
with known concentrations of Cant. The results give a lower limit of 11.4 Pg C
or 7.8% and an upper limit of 19.8 Pg C or 13.6% uncertainty of the estimated
global Cant inventory due to above assumptions, which is about half of previous
estimate. The (ii), (iv) and (iii) assumptions are the three largest source of uncertainties,
accounting for 5.5%, 3.8% and 3.0%, respectively, while the assumptions of (i)
and (iv) only contribute about 0.6% and 0.7%. Regionally, the Southern Ocean
contributes the largest uncertainty of 7.8%, while the North Atlantic contributes
about 1.3%. It suggested that spatial-dependency of Δ∕Γ, and temporal changes in
tracer saturation and air-sea CO2 disequilibrium should be considered to reduce the
uncertainty of TTD, which is increasingly important under a changing ocean climate. |
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