December 2022

Oceans are becoming acidic

This article is part of our series focused on the causes and consequences of a warming planet.

sunset over oceanAs Midwesterners, we may not pay much attention to news about the oceans. But Midwesterners are greatly affected by the impact that oceans have on our climate.

About a quarter of the world’s greenhouse gas emissions don’t remain in the atmosphere but are absorbed by the oceans. This reduces the amount of atmospheric heat created.

The absorption occurs because carbon dioxide is water soluble and easily absorbed by water. It is estimated that 30 million tons of carbon dioxide are absorbed by our oceans every day, forming weak carbonic acid.

This increase in acidity impacts life in the oceans. For example, as the acidity increases, the availability of calcium carbonate declines, which is an important building block for sea life with shells and skeletons. This increasing acidity has a dramatic negative impact on shelled species such as oysters, shrimp, lobsters, clams, sea urchins, and calcareous plankton.

A measure of acidity is the pH scale, which runs from 0 to 14. Low numbers are acidic and high numbers are basic. Seven, the halfway mark, is neutral. Ocean pH has been slightly basic over the last 300 million years, averaging about 8.2. The current ocean pH is around 8.1. This small drop represents a 25% increase in acidity. By the end of the century with continued carbon dioxide emissions, ocean pH could drop to 7.6, a substantial reduction in the survival of sea life. This would be an acidity level not experienced for more than 20 million years.

Unless we control greenhouse gas emissions, ocean organisms may need to find a way to adapt to these substantial and rapid changes in the oceans or perish. However, recent research indicates the capacity of the oceans to absorb more carbon dioxide in the future seems to be diminishing. Although good news for the oceans, this will result in a larger buildup of carbon dioxide in the atmosphere, resulting in faster atmospheric warming and climate change.

See the Ag Decision Maker website for more from this series.

Don Hofstrand, retired extension agricultural business specialist,
Reviewed by Dr. Eugene Takle, retired professor emeritus Iowa State University


Don Hofstrand

retired extension agricultural business specialist
View more from this author
Reviewed by

Dr. Eugene Takle

retired professor emeritus Iowa State University