炭酸系観測データから推定した北太平洋亜熱帯域における酸性化の状況 Ocean acidification in the subtropical North Pacific estimated from accumulated carbonate data

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Abstract

   人為起源CO<sub>2</sub>の吸収・蓄積に伴い、海洋表層の全炭酸濃度が長期的に増加し、酸性化を引き起こす。海洋の酸性化が今後さらに進行した場合、海洋生態系に大きな影響を及ぼすことが懸念されている。北太平洋亜熱帯域においてこれまでに取得・蓄積されてきた海水中CO<sub>2</sub>分圧等の炭酸系観測データを使用して、pHの高精度観測が行われていない期間における東西各海域のpH時系列を推定した。北太平洋亜熱帯の各海域で見積られたpHは、いずれも長期的に有意な低下傾向(年平均変化率-0.001~-0.002yr<sup>-1</sup>)を示した。水温変化の寄与を除いたpHの低下速度は、亜熱帯東部で大きい。亜熱帯東部では、亜寒帯系の高全炭酸水が流入して酸性化を加速させている可能性が見出された。また、pHの低下は、40年前に比べて近年加速しており、今後のCO<sub>2</sub>の排出シナリオに応じてさらに速くなると推定された。

   The recent uptake of anthropogenic carbon by the ocean brings about changes in the surface-ocean carbon cycle that could result in ocean acidification with subsequent serious effects on marine ecosystems. We evaluated the trend of ocean acidification in the surface layer of extensive regions of the subtropical North Pacific using synthesized data for partial pressure of CO<sub>2</sub> for the past 40 years because no precise pH data were available. The results show significant trends of acidification (a pH decrease of 0.01 to 0.02 per decade) over the subtropical North Pacific. The rate of pH decrease, after excluding the contribution from changes in sea surface temperature, was highest in the eastern subtropical region. In this region in particular, the intrusion of subarctic waters with high concentrations of dissolved inorganic carbon could have contributed to the relatively high rate of acidification. Comparisons of the estimated rate of pH decrease for the past 26 years with those for the decade following 1969 and for 50 years into the future suggest an acceleration of acidification in recent years, as well as in the future, depending on the scenario of future anthropogenic CO<sub>2</sub> emission.

Journal

  • Papers in Meteorology and Geophysics

    Papers in Meteorology and Geophysics (62), 47-56, 2011

    Japan Meteorological Agency / Meteorological Research Institute

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