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Spatial variability and decadal trend of the oceanic CO2 in the western equatorial Pacific warm/fresh water

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Title: Spatial variability and decadal trend of the oceanic CO2 in the western equatorial Pacific warm/fresh water
Authors: Ishii, Masao Browse this author
Inoue, Hisayuki Y. Browse this author →KAKEN DB
Midorikawa, Takashi Browse this author
Saito, Shu Browse this author
Tokieda, Takayuki Browse this author
Sasano, Daisuke Browse this author
Nakadate, Akira Browse this author
Nemoto, Kazuhiro Browse this author
Metzl, Nicolas Browse this author
Wong, C. S. Browse this author
Feely, Richard A. Browse this author
Keywords: Carbon dioxide
Partial pressure
Dissolved inorganic carbon
Equatorial Pacific
Decadal trend
Issue Date: Apr-2009
Publisher: Elsevier Ltd.
Journal Title: Deep Sea Research Part II : Topical Studies in Oceanography
Volume: 56
Issue: 8-10
Start Page: 591
End Page: 606
Publisher DOI: 10.1016/j.dsr2.2009.01.002
Abstract: Data of the partial pressure of carbon dioxide in surface seawater (pCO2sw) collected in the western equatorial Pacific (144°E - 160°W, 5°S - 5°N) since the 1980's have been used to determine the spatial variability and decadal trends in pCO2sw. A total of 109 cruises since 1983, including 30 cruises since 1990 with total dissolved inorganic carbon (TCO2) measurements, are synthesized for this zone. The western equatorial Pacific warm/fresh surface water where T ≥ 29.0 ℃ and S ≤ 34.8 is nitrate-depleted and it is moderately supersaturated with CO2 (0 < ΔpCO2 (= pCO2sw - pCO2air) / μatm < 40). A slight CO2 undersaturation (-20 < ΔpCO2 / μatm < 0) was also observed on many cruises where thin, low density layers (σt < 21.4) capped barrier layers. The undersaturation may result from net biological uptake of CO2 due to nitrogen fixation. Excluding the data in such a extremely light waters, we determined changes in the linear growth rate of pCO2sw of +0.3 ± 1.3 μatm year^[-1] for 1985 - 1990, +2.2 ± 0.7 μatm year^[-1] for 1990 - 1999, and -0.2 ± 1.0 μatm year^[-1] for 1999 - 2004. The rate of increase was +1.5 ± 0.2 μatm year^[-1] for the entire period (1985 - 2004). The variation in the rate of increase of pCO2sw is fairly consistent with the change in the rate of increase of salinity-normalized TCO2 from +2.1 ± 0.4 μmol kg^[-1] year^[-1] during 1992 - 1999 to +0.4 ± 0.9 μmol kg^[-1] year^[-1] during 1999 - 2004. These changes are anti-correlated with the decadal variation in the geostrophic mass transport from subtropics of both hemispheres into the equatorial zone in the Pacific.
Type: article (author version)
Appears in Collections:環境科学院・地球環境科学研究院 (Graduate School of Environmental Science / Faculty of Environmental Earth Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 吉川 久幸

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