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| Titel |
Comparison of ten packages that compute ocean carbonate chemistry |
| VerfasserIn |
J. C. Orr, J.-M. Epitalon, J.-P. Gattuso |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 5 ; Nr. 12, no. 5 (2015-03-09), S.1483-1510 |
| Datensatznummer |
250117849
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| Publikation (Nr.) |
 copernicus.org/bg-12-1483-2015.pdf |
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| Zusammenfassung |
| Marine scientists often use two measured or modeled carbonate system
variables to compute others. These carbonate chemistry
calculations, based on well-known thermodynamic equilibria, are now
available in a dozen public packages. Ten of those were compared
using common input data and the set of equilibrium constants
recommended for best practices. Current versions of all 10 packages
agree within 0.2 μatm for pCO2, 0.0002 units
for pH, and 0.1 μmol kg−1 for CO32− in
terms of surface zonal-mean values. That represents more than a
10-fold improvement relative to outdated versions of the same
packages. Differences between packages grow with depth for some
computed variables but remain small. Discrepancies derive largely
from differences in equilibrium constants. Analysis of the
sensitivity of each computed variable to changes in each constant
reveals the general dominance of K1 and K2
but also the comparable sensitivity to KB for the
AT–CT input pair. Best-practice
formulations for K1 and K2 are implemented
consistently among packages. Yet with more recent formulations
designed to cover a wider range of salinity, packages disagree by up
to 8 μatm in pCO2, 0.006 units in pH, and
1 μmol kg−1 in CO32− under typical surface
conditions. They use different proposed sets of coefficients for
these formulations, all of which are inconsistent. Users would do
well to use up-to-date versions of packages and the constants
recommended for best practices. |
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