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Ocean Acidification: More CO2 = More Acidic

By Climate Central

Oceans cover 71 percent of the earth’s surface and have a huge capacity to store heat, playing a critical role in the climate system. In addition to that role, oceans are a complex and rich ecosystem on their own — helping to sustain life on land. But there are many threats to the viability of the oceans. One of them is acidification. CO2 mixes with seawater to form carbonic acid, making the oceans more acidic, which threatens food supply and the economies of coastal communities.


Ocean acidification may not be the first thing that comes to mind when you think about impacts of more CO2 in the atmosphere. But currently, oceans absorb about a quarter of the CO2 humans produce every year. All gases in the atmosphere interact with seawater, but when CO2 mixes with the water, it forms carbonic acid. Increased carbonic acid leads to the depletion of carbonate ions, which are an essential component of minerals vital for building sea shells.

Acidity is measured on the pH scale, where 0 is most acidic, 7 is neutral, and 14 is most basic (a base is the opposite of an acid). Since the industrial revolution, the ocean pH has dropped from 8.2 to 8.1. While that does not sound like much, that's a 30 percent increase in acidity. Each digit on the scale indicates a change by a factor of 10. So, a pH of 7 is 10 times more acidic than an 8. At current emission rates, ocean pH may drop to 7.8 by the end of the century, creating an ocean more acidic than any seen in the past 100 million years.

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