Caldeira Lab Research:Ocean acidification and ocean carbon cycle

Atmospheric CO2 stabilization and ocean acidification

Long Cao & Ken Caldeira

An exploration of the effects of atmospheric CO2 concentration on the chemistry of the ocean. High CO2 concentrations cause an undersaturation of aragonite in the ocean surrounding coral reefs as well as an overall reduction in oceanic pH levels. This displays the possibility for serious damage to the ocean's ecosystems.

Cao, L; Caldeira, K, 2008. Atmospheric CO2 stabilization and ocean acidification, Geophysical Research Letters 35 (19), DOI: 10.1029/2008GL035072.


Atmospheric CO2 concentration's effect on pH and aragonite saturation: pH lowers concurrently with rising CO2 concentrations, as does aragonite saturation. These kinds of changes to ocean chemistry could have dire consequences for marine life, especially coral reefs.


We use a coupled climate/carbon-cycle model to examine the consequences of stabilizing atmospheric CO2 at different levels for ocean chemistry. Our simulations show the potential for major damage to at least some ocean ecosystems at atmospheric CO2 stabilization levels as low as 450 ppm. Before the industrial revolution, more than 98% of corals reefs were surrounded by waters that were >3.5 times saturated with respect to their skeleton materials (aragonite). If atmospheric CO2 is stabilized at 450 ppm only 8% of existing coral reefs will be surrounded by water with this saturation level. Also at this CO2 level 7% of the ocean South of 60_S will become undersaturated with respect to aragonite, and parts of the high latitude ocean will experience a decrease in pH by more than 0.2 units. Results presented here provide an independent and additional basis for choosing targets of atmospheric CO2 stabilization levels.