Caldeira Lab Research:Ocean acidification and ocean carbon cycle

Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean

Ken Caldeira & Michael E. Wickett

Continued CO2 emissions in the future are likely to create major changes in the chemistry of the ocean, including a reduction in aragonite and calcite saturation as well as a reduction in pH. This paper presents the effects on ocean chemistry in several different modeled situations, including continued unchecked emissions, eventual stabilization of CO2 levels, and stabilization obtained through deep sea injection of carbon dioxide. The results show that even in the best case scenario CO2 emissions could have serious effects on marine life in the future.

Caldeira, K., and M.E. Wickett, Ocean model predictions of chemistry changes from carbon dioxide emissions to the atmosphere and ocean. Journal of Geophysical Research (Oceans) 110, C09S04, doi:10.1029/2004JC002671, 2005.

Change in pH and mineral saturation for 2100 and 2300 for concentration stabilization: Predicted reductions in pH and mineral saturation for various CO2 stabilization scenarios in the years 2100 and 2300. This includes stabilization at levels from 450 to 1000ppm. Each situation resulted in a drop in both pH and mineral saturation.

Changes in precipitation In the same two experimental simulations. (a) and (b) are again our climate simulated with twice the CO2 concentration from before the Industrial Revolution, while (c) and (d) are the climate with a 1.84% uniform reduction in insolation. The left column shows the precipitation change relative to pre Industrial Revolution levels, while the right column shows where in the world this change is statistically significant.


We present ocean chemistry calculations based on ocean general circulation model simulations of atmospheric CO2 emission, stabilization of atmospheric CO2 content, and stabilization of atmospheric CO2 achieved in total or in part by injection of CO2 to the deep ocean interior. Our goal is to provide first-order results from various CO2 pathways, allowing correspondence with studies of marine biological effects of added CO2. Parts of the Southern Ocean become undersaturated with respect to aragonite under the Intergovernmental Panel on Climate Change Special Report on Emissions Scenarios (SRES) A1, A2, B1, and B2 emission pathways and the WRE pathways that stabilize CO2 at 650 ppm or above. Cumulative atmospheric emission of 5,000 Pg C produces aragonite undersaturation in most of the surface ocean; 10,000 Pg C also produces calcite undersaturation in most of the surface ocean. Stabilization of atmospheric CO2 at 450 ppm produces both calcite and aragonite undersaturation in most of the deep ocean. The simulated SRES pathways produce global surface pH reductions of ≈0.3–0.5 units by year 2100. Approximately this same reduction is produced by WRE650 and WRE1000 stabilization scenarios and by the 1250 Pg C emission scenario by year 2300. Atmospheric emissions of 5000 Pg C and 20,000 Pg C produce global surface pH reductions of 0.8 and 1.4 units, respectively, by year 2300. Simulations of deep ocean CO2 injection as an alternative to atmospheric release show greater chemical impact on the deep ocean as the price for having less impact on the surface ocean and climate. Changes in ocean chemistry of the magnitude shown are likely to be biologically significant.