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Titel |
Ocean acidification from 1997 to 2011 in the subarctic western North Pacific Ocean |
VerfasserIn |
M. Wakita, S. Watanabe, M. Honda, A. Nagano, K. Kimoto, K. Matsumoto, M. Kitamura, K. Sasaki, H. Kawakami, T. Fujiki, K. Sasaoka, Y. Nakano, A. Murata |
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 ; 10, no. 12 ; Nr. 10, no. 12 (2013-12-02), S.7817-7827 |
Datensatznummer |
250085450
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Publikation (Nr.) |
copernicus.org/bg-10-7817-2013.pdf |
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Zusammenfassung |
Rising atmospheric CO2 contents have led to greater CO2 uptake by
the oceans, lowering both pH due to increasing hydrogen ions and CaCO3
saturation states due to declining carbonate ion (CO32−). Here we
used previously compiled data sets and new data collected in 2010 and 2011
to investigate ocean acidification of the North Pacific western subarctic
gyre. In winter, the western subarctic gyre is a source of CO2 to the
atmosphere because of convective mixing of deep waters rich in dissolved
inorganic carbon (DIC). We calculated pH in winter mixed layer from DIC and
total alkalinity (TA), and found that it decreased at the rate of −0.0011 ± 0.0004 yr−1 from 1997 to 2011. This decrease rate is slower
than that expected under the condition of seawater/atmosphere equilibration, and
it is also slower than the rate in the subtropical regions (−0.002 yr−1). The slow rate is caused by a reduction of CO2 emission in
winter due to an increase in TA. Below the mixed layer, the calcite
saturation horizon (~ 185 m depth) shoaled at the rate of 2.9 ± 0.9 m yr−1 as the result of the declining CO32−
concentration (−0.03 ± 0.01 μmol kg−1 yr−1).
Between 200 m and 300 m depth, pH decline during the study period
(−0.0051 ± 0.0010 yr−1) was larger than ever reported in the open North
Pacific. This enhanced acidification rate below the calcite saturation
horizon reflected not only the uptake of anthropogenic CO2 but also the
increase in the decomposition of organic matter evaluated from the increase
in AOU, which suggests that the dissolution of CaCO3 particles
increased. |
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