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| Titel |
Carbonate system in the water masses of the Southeast Atlantic sector of the Southern Ocean during February and March 2008 |
| VerfasserIn |
M. González-Dávila, J. M. Santana-Casiano, R. A. Fine, J. Happell, B. Delille, S. Speich |
| 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 ; 8, no. 5 ; Nr. 8, no. 5 (2011-05-31), S.1401-1413 |
| Datensatznummer |
250005829
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| Publikation (Nr.) |
 copernicus.org/bg-8-1401-2011.pdf |
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| Zusammenfassung |
Carbonate system variables were measured in the South Atlantic sector of the
Southern Ocean along a transect from South Africa to the southern limit of
the Antarctic Circumpolar Current (ACC) from February to March 2008. Eddies
detached from the retroflection of the Agulhas Current increased the
gradients observed along the fronts. Minima in the fugacity of CO2,
fCO2, and maxima in pH on either side of the frontal zone were observed,
noting that within the frontal zone fCO2 reached maximum values and pH
was at a minimum.
Vertical distributions of water masses were described by their carbonate
system properties and their relationship to CFC concentrations. Upper
Circumpolar Deep Water (UCDW) and Lower Circumpolar Deep Water (LCDW)
offered pHT,25 values of 7.56 and 7.61, respectively. The UCDW also had
higher concentrations of CFC-12 (>0.2 pmol kg−1) as compared to
deeper waters, revealing that UCDW was mixed with recently ventilated
waters. Calcite and aragonite saturation states (Ω) were also
affected by the presence of these two water masses with high carbonate
concentrations. The aragonite saturation horizon was observed at 1000 m in
the subtropical area and north of the Subantarctic Front. At the position of
the Polar Front, and under the influence of UCDW and LCDW, the aragonite
saturation horizon deepened from 800 m to 1500 m at 50.37° S, and
reached 700 m south of 57.5° S. High latitudes proved to be the most
sensitive areas to predicted anthropogenic carbon increase. Buffer
coefficients related to changes in [CO2], [H+] and Ω with
changes in dissolved inorganic carbon (CT) and total alkalinity
(AT) offered minima values in the Antarctic Intermediate Water and UCDW
layers. These coefficients suggest that a small increase in CT will
sharply decrease the status of pH and carbonate saturation. Here we present
data that suggest that south of 55° S, surface water will be
under-saturated with respect to aragonite within the next few decades. |
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