This Is Where Humans Have Made Our Oceans Most Acidic

Is an ocean near you dissolving sea bones? The most comprehensive study yet of the globe's acidifying oceans will tell you.

Brian Merchant

Brian Merchant

Since the beginning of the Industrial Revolution, humans have driven the world's oceans to become 30 percent more acidic. The oceans absorb about a quarter of the carbon dioxide released into the atmosphere each year—a volume that has skyrocketed in recent decades—which in turn raises their acidity. Your city's cars and power plants are making the ocean's pH drop, in other words.

That's the widely-accepted theory, anyway. Ocean acidification has been examined in a number of regions (in some parts of the Pacific, the ocean is already so acidic it's dissolving sea snails' shells) and extensively modeled. But we lacked a comprehensive, data-supported picture of what the phenomenon looked like on a global scale. 

Enter Columbia University's Taro Takahashi and his team, who have just published research that paints "the most comprehensive picture yet of how acidity levels vary across the world's oceans," and presents the results in a series of detailed maps.

"I started out from a neutral point to prove or disprove whether that information was correct or not," he told me in an interview. "What I found was that it was being acidified according to the carbon dioxide released into the atmosphere."

No surprise there—but, as Takahashi says, it's "good to know" for sure, so we can plan for the future.

"The main point is that I am laying a foundation, in 2005, of where the ocean was," Dr. Takahashi said. Until now, "there was no global observation of data." 

The ocean's pH levels in 2005—red is a mellow alkaline, purple is acidic as hell.

So, Takahashi analyzed four decades' worth of ocean data to better pinpoint where the acidity was greatest. The Indian Ocean, it turns out, is ten percent more acidic than average. And colder oceans near the poles are acidifying far more rapidly than temperate ones. Waters near Iceland as well as the Antarctic Ocean, for instance, are acidifying at an astonishing rate of five percent per decade. 

Right now, his research suggests that the Bering Strait is the most acidic place on Earth during the winter.

So why does this matter? Marine ecosystems can tolerate small pH drops; they're used to some acid swings. But when oceans get too acidic, they can prevent shellfish from forming shells, or result in deadly coral bleaching, for example. In the Arctic Ocean, which we now know is becoming much more acidic, levels of the mineral aragonite have fallen, which makes it harder for tiny, bottom-of-the-food-chain sea snails to grow—thus decreasing the food supply for Arctic fish. 

Levels of aragonite in the oceans—some sea creatures need this stuff to grow their shells.

And while no scientist can be sure what, exactly, will happen as the oceans absorb even more CO2, we're heading towards a tipping point where oceans will be more acidic more of the time.

"Ocean acidity changes seasonally up and down," Takahashi told me, "so the marine ecosystem is used to fluctuations in acidity. But by 2050, it's going outside of the normal seasonal changes." 

And that's when we could see some serious problems. His findings are in line with those of Europe's Environment Agency, which also found that beginning around 2050, marine animals like coral would have serious trouble growing

Takahashi stresses that as with the CO2 rise in the atmosphere, there will be winners and losers in the marine world, and that it's impossible to predict what will shake out. But he still sounds concerned.

"We should take care of our oceans. Many human lives rely on it," he told me. "We don't want to see a catastrophic change in the oceans; that would have a dramatic effect on human life."