Daily Earth Science Environment Hydrosphere Repost

Ocean Acidification

Most people associate climate change with increased greenhouse gases in the atmosphere. But the role of greenhouse gases in the oceans is not as well understand. Climate change affects the oceans in more ways than just sea-level rise. An intricate relationship exists between the atmosphere and ocean chemistry. Part of this ocean/atmosphere relationship is ocean acidification. 

Oceans cover about 71% of the surface of the planet. Where the ocean and atmosphere meet, they interact and exchange carbon dioxide (CO2). The earth’s current CO2 budget dictates that when CO2 enters the atmosphere from burning fossil fuels, only about 45% of that CO2 stays in the atmosphere. Land plants use about 25% of the emitted CO2, and then the oceans absorb the remaining 30%. Since colder water absorbs more CO2 than warmer water, Arctic oceans are more significant reservoirs for CO2 than tropical waters.

Carbonate buffering is the name given to the CO2 exchange process between the atmosphere and the oceans. When the CO2 enters the ocean, it reacts with water to form carbonic acid, and this causes ocean acidification.

Buffering is a reversible set of chemical reactions. As atmospheric CO2 increases, the oceans become more acidic (lower pH). If atmospheric CO2 drops, then the sea reverses the reaction and returns CO2 to the atmosphere. The earth’s oceans hold about 93% of the CO2 reserves on the planet’s surface, so their role in regulating atmospheric CO2 is critical.

Where are we now?

The industrial revolution was in full swing by 1830. For the 10,000 years before the industrial revolution, the atmospheric CO2 level held steady between 260 – 290 parts per million (ppm). But, between 1830 and 1950, atmospheric CO2 moved up to 310 ppm. Since 1950, it has risen to 411 ppm, or a 50% increase from the beginning of the industrial revolution.

Atmospheric CO2 from 1700 to present (From Scripps Institution of Oceanography)

Carbonate buffering informs us that rising CO2 in the atmosphere creates significant ocean acidification. Dissolved CO2 in the oceans has increased by about a third since 1850, and ocean pH has dropped from 8.16 to 8.05. The 0.11 change doesn’t seem like much, but it represents a 33% increase in acidity since the pH scale is logarithmic. 

What does it mean?

The effects of ocean acidification start at the bottom of the food chain. Higher acidity decreases the amount of calcium carbonate available for small planktonic creatures to make their shells. Groups like pteropods are an important planktonic component at the base of the food chain, and without the plankton, the ocean ecosystem collapses. If plankton can’t produce viable shells because of increasing acidity, then the species won’t survive, and the ocean’s fish populations dependent on those plankton will decline. 

Oceans are a vital resource for humans, and more than 3.0 billion people on the planet depend on fish as a primary source of protein. Ocean acidification is real. It is a significant consequence of human-made climate change and a material threat to key food chains that sustain our societies.


A crab crisis from coastal water acidification (Source: ArcheanWeb) – https://archeanweb.com/2020/01/31/a-crab-crisis-from-coastal-water-acidification/ Also:

Acid and phytoplankton in the ocean’s food chain (Source: ArcheanWeb) – https://archeanweb.com/2020/01/28/acid-and-phytoplankton-the-oceans-food-chain/ Also:


What is carbonate buffering? (John Brennan –  Sciencing) – https://sciencing.com/carbonate-buffering-8299150.html Also:

What is happening in the ocean (NASA Climate Kids) – https://climatekids.nasa.gov/ocean/ Also:

Ocean-Atmosphere CO2 Exchange (NOAA – Science on a Sphere) – https://sos.noaa.gov/datasets/ocean-atmosphere-co2-exchange/ Also:

How much CO2 can the oceans take up? (Rob Monroe – Scripps Institution of Oceanography) – https://scripps.ucsd.edu/programs/keelingcurve/2013/07/03/how-much-co2-can-the-oceans-take-up/ Also:

Learn about 5 scary consequences to ocean acidification (Dolphinaris) – https://www.dolphinaris.com/learn-about-5-scary-consequences-to-ocean-acidification/ Also:

Acids, bases, & the pH scale (Science Buddies) – https://www.sciencebuddies.org/science-fair-projects/references/acids-bases-the-ph-scale Also:

Feature Image: Waves at La Corniche (By Christian Ferrer) (Modified) – https://commons.wikimedia.org/wiki/File:Waves_at_La_Corniche.jpg – This file is licensed under the Creative Commons Attribution 4.0 International license. – https://creativecommons.org/licenses/by/4.0/deed.en

William House
William is an earth scientist and writer with an interest in providing the science "backstory" for breaking environmental, earth science, and climate change news.