This indicator shows acidity levels in the ocean, which are strongly affected by the amount of carbon dioxide in the water.
- Measurements made over the last few decades have demonstrated that ocean carbon dioxide levels have risen, accompanied by an increase in acidity (that is, a decrease in pH) (see Figure 1).
- Modeling suggests that over the last few centuries, ocean acidity has increased globally (meaning pH has decreased), most notably in the Atlantic (see Figure 2).
- Direct observations show that pH levels fluctuate more frequently in some areas of the ocean than in others. 3 More measurements are needed to better understand the links between these natural fluctuations and long-term changes in ocean acidity.
US Environmental Protection Agency (EPA). Web page.