Oceans are acidifying faster than ever

Acidity in the Earth's oceans is increasing more rapidly than any time in the last 300 million years, leading to severe consequences for marine ecosystems.

An animation showing a computer forecast of how the ocean pH will look in 2100 under emission scenarios. Purple dots show cold-water coral reefs. Red dots show warm-water coral reefs. The pH scale is shown on the right. NOAA

The burning of fossil fuels and the release of carbon dioxide into the atmosphere don't affect just the air--it also impacts the Earth's oceans, according to U.S. National Oceanic and Atmospheric Administration (NOAA).

Oceans absorb the carbon dioxide, which in turn changes the water's pH acidity levels. What this means is that coral reefs are growing at a slower rate and the survival of marine species is decreasing, according to NOAA.

Now, the speed at which ocean pH level is changing is faster than any time in the last 300 million years, according to a new study published in the journal Science today.

"Ocean acidification may have severe consequences for marine ecosystems," reads the study. "However, assessing its future impact is difficult because laboratory experiments and field observations are limited by their reduced ecologic complexity and sample period."

To combat this obstacle, the scientists working on the study looked at ancient climate records dating back 300 million years to study marine and animal extinction and evolutionary changes, such as when the dinosaurs were killed off 65 million years ago.

They came upon a unique case 56 million years ago when there was a massive emission of carbon into the atmosphere that occurred naturally, which they believe was caused by volcanoes. With this data, the scientists then tried to decipher possible impacts they could translate to better understand modern-day climate change.

Back then, the average temperature rose by 10.8 degrees, the oceans became 0.4 units more acidic on the 14-point pH scale, and many types of coral went extinct, according to the study. This change happened over a 5,000-year period.

One of the study's authors, Baerbel Hoenisch, told Reuters in an interview that what happened 56 million years ago was a fast warm-up and quick acidification, but was small compared with what has happened on Earth since the start of the industrial revolution 150 years ago.

Over the past 150 years, the earth's oceans have become more acidic by 0.1 unit of pH, and the study's scientists predict that by 2100 there will be an increase to 0.2 or 0.3 pH.

"Given that the rate of change was an order of magnitude smaller compared to what we're doing today, and still there were these big ecosystem changes, that gives us concern for what is going to happen in the future," Hoenisch said.

This story was corrected at 11:56 a.m. PT Friday to clarify how carbon dioxide affects the oceans' pH acidity.

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About the author

Dara Kerr, a freelance journalist based in the Bay Area, is fascinated by robots, supercomputers and Internet memes. When not writing about technology and modernity, she likes to travel to far-off countries.

 

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