Approximately half of the man-made carbon dioxide emissions since the industrial revolution have been absorbed by the oceans. This process, also known as the solubility pump (see link for more detail), acts as a buffer to atmospheric increases in CO2 which lead to warming. However, in the absorption of CO2 by the oceans, a form of acid (carbonic acid) is formed. This has caused an overall reduction in the pH of the oceans, or an increase in the acidity.
An understanding of the full impacts of ocean acidification is at a relatively early stage. As such, there is more work to do in order to fully understand how the oceans interact with the atmposphere, their capacity to continue to act as a carbon sink and the impact on any sea ecosystems. However, continuing increases in the acidity of the oceans is highly likely to impact on sensitive marine environments such as corals. Increased levels of coral bleaching have been observed and linked to increased acidity. Other shell based organisms are also thought to be particularly sensitive to changes in the pH of the oceans.
