2011 Volume 62 Pages 47-56
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 CO2 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 CO2 emission.
