KEY FACTS
What is already happening
- Atmospheric CO2 exceeded 414 ppm in 2021 and has continued to increase by approximately 2.4 ppm per year over the last decade. The global ocean absorbs approximately a quarter of anthropogenic carbon dioxide (CO2) emissions annually.
- The North Atlantic Ocean contains more anthropogenic CO2 than any other ocean basin, and surface waters are experiencing an ongoing decline in pH (increasing acidity). Rates of acidification in bottom waters are occurring faster at some locations than in surface waters.
- Some species are already showing effects from ocean acidification when exposed to short-term fluctuations and could be used as indicator species for long-term impacts on marine ecosystems.
What could happen in the future
- Models project that the average continental shelf seawater pH will continue to decline to year 2050 at similar rates to the present day, with rates then increasing in the second half of the century, depending on the emissions scenario.
- The rate of pH decline in coastal areas is projected to be faster in some areas (e.g. Bristol Channel) than others, such as the Celtic Sea.
- Under high-emission scenarios, it is projected that bottom waters on the North-West European Shelf seas will become corrosive to more soluble forms of calcium carbonate (aragonite). Episodic undersaturation events are projected to begin by 2030.
- By 2100, up to 90% of the north-west European shelf seas may experience undersaturation for at least one month of each year.
- High levels of nearshore variability in carbonate chemistry may mean that some coastal species have a higher adaptative capacity than others. However, all species are at increased risk from extreme exposure episodes.
Findlay H.S., Artoli Y., Birchenough S.N.R., Hartman S., León P. and Stiasny M., in press. Climate change impacts on ocean acidification relevant to the UK and Ireland. MCCIP Science Review. Article.
