Effects of CO2 on the ocean environment

The most immediate environmental effect of solving CO2 in the ocean is a reduction of the pH. The present rate of change of pH in the surface mixed layer due to invasion of anthropogenic CO2 from the atmosphere is close to 0.015 pH units per decade. A cumulative reduction of 0.1 units has already taken place during the past 200 years, and a further reduction of 0.2 to 0.3 pH units may occur in the next century. This perturbation may be compared to the existing range of pH in the world ocean of 0.5 pH units, a seasonal amplitude of up to 0.1 pH units locally, and to glacial to interglacial variations of 0.2-0.3 pH units in 10000 years (0.0003 pH units per decade). Emissions to the atmosphere expose species in almost all ocean surface waters, including high productivity zones, to permanent and uniform reduction of pH. Disposal of CO2 at fixed locations in the ocean can give strong maximum pH reduction at depth where natural variability in pH is smaller and tolerance limits for biota probably narrower.