365 Days of Climate Awareness 12 - Ocean Acidification

365 Days of Climate Awareness

12 - Ocean Acidification

As carbon dioxide continues to enter the atmosphere from combustion of fossil fuels, roughly 30% is absorbed by the ocean. CO₂ in the ocean does not have the insulating effect it does in the atmosphere--water is quite efficient enough itself in retaining heat--but it does affect the chemistry.

pH means "power of Hydrogen", and measures alkalinity versus acidity. Neutral pH is 7. Alkalines are higher on the scale (typically between 7 and 14, but very strong alkalines are higher). Acids typically measure between 0 and 7, but extremely strong acids have negative pH. The global mean for pH of the ocean was 8.2 prior to the Industrial Revolution, and is now 8.1. The ocean is becoming more acidic, because of the added CO₂. When carbon dioxide goes into solution in water, the reaction forming carbonic acid takes place:

    H₂O + CO₂ <--> H + HCO₃-

Only a low percentage of dissolved CO₂ becomes this acid, but it's been enough to make the global ocean more acidic, with widespread effects. Many animals and microscopic plankton produce their own shells from minerals absorbed from seawater. But in the increasing acidity--the dropping pH--of the ocean, those shells are dissolving again, leaving a growing number of sea creatures without their ordinary form of protection. The lowering pH also impacts coral reefs: along with rising temperatures it causes the corals to lose their color ("bleach") and then die.

Mean oceanic pH over the past 25 million years

Tomorrow: eustatic sea level.

Be well!