Ocean acidification in the western North Pacific subtropical and tropical zones

Abstract

We analysed the seasonal variations and long-term trend of total CO₂, pH and saturation index of aragonite in the western North Pacific tropical and subtropical zone on the basis of the measurements of the partial pressure of CO₂ in surface water that have been made by MRI and JMA along 137E and its adjacent regions since early 1980s. In the northern subtropics, seasonal variations are remarkable and long-term trend of TCO₂ increase and ocean acidification that are consistent with the rate of the atmospheric CO₂ rise have been determined. In the southern subtropics and in the tropics, seasonal variation is small and the mean rates of TCO₂ increase and ocean acidification for the past three decades are smaller than in the northern subtropics.