Ishii et al. from Japan’s Environment and Marine Department has analyzed time series observations of many oceanic CO2 parameters measured just off the southern coast of Honshu, Japan. Their measurements, spanning a 14-year period from 1994-2008, consisted of partial pressures of CO2, pH levels, aragonite saturation rates, and calcite saturation rates. The results from Ishii’s analysis shows a moderate trend of increasing pCO2 levels, and decreasing pH levels, aragonite saturation rates, and calcite saturation rates over the 14-year period. The trends discovered in the study all show that ocean acidification is continuing to intensify and particularly threatening calcifying species with the declining aragonite and calcite saturation rates. However, the data show a very significant seasonal pattern where pH and carbonate saturation rates peak during the summer months and dip in the winter months. Ishii et al. attributed this to the lower water temperatures as well as upwelling of CO2 rich waters up to the surface during the winter months.

Journal of Geophysical Research 116, 649-659 (2010)