Environment

The seafloor is dissolving, thanks to human activity

A new study has found that human activity is dissolving the seafloor
A new study has found that human activity is dissolving the seafloor
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A research vessel investigating the effects of human-created carbon dioxide emissions on the seafloor, which is found to be dissolving at an increased rate
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A research vessel investigating the effects of human-created carbon dioxide emissions on the seafloor, which is found to be dissolving at an increased rate
Oceanographer Robert Key aboard a research vessel near Antarctica
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Oceanographer Robert Key aboard a research vessel near Antarctica
A map of the parts of the ocean that are experiencing the most extreme seafloor dissolution, thanks to carbon dioxide emissions
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A map of the parts of the ocean that are experiencing the most extreme seafloor dissolution, thanks to carbon dioxide emissions
A new study has found that human activity is dissolving the seafloor
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A new study has found that human activity is dissolving the seafloor

Excess carbon dioxide isn't just building up in the atmosphere – the oceans are holding onto more of the stuff too, fizzing them up like soda. As the seas get warmer and more acidic, all kinds of havoc is wrought, and now a new study has identified yet another symptom. Researchers at Princeton and McGill Universities have found that the seafloor is beginning to dissolve as a result of human activity.

According to the Smithsonian's Ocean Portal organization, about 525 billion tons of CO2 has been absorbed by the world's oceans since the beginning of the industrial era, making seawater up to 30 percent more acidic than it was 200 years ago. That makes it the fastest known change in ocean chemistry in 50 million years or so, and the effects have already been devastating.

Ocean acidification is contributing to coral bleaching, upsetting predator/prey relationships, messing with the survival instincts of fish, and even dissolving certain sea creatures. And now we have a new problem to add to the ever-growing list: pockets of acidic water are reaching the bottom of the ocean and destroying the seabed.

A research vessel investigating the effects of human-created carbon dioxide emissions on the seafloor, which is found to be dissolving at an increased rate
A research vessel investigating the effects of human-created carbon dioxide emissions on the seafloor, which is found to be dissolving at an increased rate

A healthy seafloor is made mostly of calcite, which comes from the decomposed remains of plankton and other sea creatures. But increased CO2 levels are quickly ramping up the acidity and eating away at the calcite. In the worst hit areas, such as the Northern Atlantic and the southern oceans, the normally chalky-white material is becoming a muddy brown color.

The new study investigated the extent of the dissolving seafloor, and how much blame belongs to human influence. Basically, the deepest parts of the sea are already fairly acidic, thanks to higher pressure, lower temperature and stored CO2. But closer to the surface, conditions are less hostile, meaning calcium carbonate particles will accumulate on the seafloor at shallower depths. The point where the two transition is called the calcite compensation depth (CCD).

This depth is one of the main metrics of seafloor dissolution, since anything below that point will dissolve. The study examined recent databases of bottom-water chemistry and other conditions in the western North Atlantic Ocean, and found that the CCD there has risen by about 300 m (984 ft) since the beginning of the industrial era.

A map of the parts of the ocean that are experiencing the most extreme seafloor dissolution, thanks to carbon dioxide emissions
A map of the parts of the ocean that are experiencing the most extreme seafloor dissolution, thanks to carbon dioxide emissions

In the lab the team recreated the seafloor at different depths, to get a better understanding of what factors influence the dissolution of calcite. By modeling and comparing the rates of seafloor dissolution from preindustrial and modern times, the team was able to calculate the amount that can be classed as human-induced. In the Northern Atlantic, this was between 40 and 100 percent.

"For decades we have been monitoring the increasing levels of anthropogenic carbon dioxide as it moves from the atmosphere into the abyssal ocean," says Robert Key, co-author of the study. "While expected, it is none the less remarkable that we can now document a direct influence of that process on carbonate sediments. It will be really interesting to see if we can further support this result with new data generated by autonomous floats in the Southern Ocean."

The next steps for the team are to model the seabeds based on predictions of future carbon dioxide scenarios, to determine how fast seafloors might be dissolving over the next few centuries.

The research was published in the journal Proceedings of the National Academy of Sciences.

Sources: Princeton University, McGill University

13 comments
Anne Ominous
This doesn't add up. 525 billion tons CO2 = 4.76 x 10^14 kg. There are about 1.4 x 10^21 kg of ocean water. Or nearly 7 orders of magnitude more ocean mass than than much CO2. Even when it's converted to molar equivalents, there is no possible way that much CO2 could "acidify" that much ocean by "30%". It simply isn't possible. Especially considering that the ocean is already a buffered solution, so adding CO2 doesn't simply acidify it... it takes a lot more CO2 than it would for, say, tap water.
Rumata
Let's face the facts. 1. Solved CO2 can make only sweetwater acidic. The salt content of seawater makes it definitely basic, and carbonic acid is too weak to turn it acidic. Only undersea vulcanic activities (like underwater gas eruptions with sulfur content) can make seawater locally acidic. Only totally uneducated people can belive that solved CO2 can make seawater acidic. 2. The ocean already stores 140,000 billion tons of solved CO2 in it. Hence, the 525 billion tons of human CO2 makes only 0,37% of it. So the 525 billion tons of CO2 can't make any measureable effect. Even if all known fossil fuel reseve on Earth were burned, it could increase the CO2 content of the oceans only by 10,7%. And even then the chemistry of oceans would remain basic. 3. During Cretaceous Age, the atmospheric CO2-level was 4 times higher than today. And that was the time, when the the greatest population of sea creatures with calcum carbonate skeletone were living. 4. Anybody, who had ever seen a soda bottle, should understand at once, that the oceans regulate the atmospheric CO-level. If the temperature is higher, then the equilibrium pressure of CO2 above the soda water will be higher. If the temperature is lower, then the equilibrium pressure of CO2 above the soda water will be lower. If there is more CO2, then the soda water will sink the excess amount to restore the equilibrium. If there is less CO2, then the soda water release the needed amount to restore the equilibrum. 5. There is no measureable correlation between the yearly amount of human CO2 emission and the yearly increase of atmospheric CO2-level, because the oceans regulates the CO2-level in the air. But there is a strong correlation between the global average temperature of a given year and the yearly increase of CO2-level in the air, because it is determined only by the yearly warming of the surface of oceans.
Subtle
That the ocean floors are dissolving is good news. It means that the top side of the seas will no longer be rising. Of course, this is sarcasm. I'm a geophysicist and agree with the two earlier posts. Good that you published them.
piperTom
The article says "as the seas get ... more acidic, all kinds of havoc is wrought" in the minds of those who love havoc. As the oceans' pH descends from about 8.0 to 7.9, it has still a way to go before it hits *neutral*. So, the seas are getting more NEUTRAL and ... this is havoc?
ljaques
OhMyGodWe'reAllGonnaDieAgainAgainAgain! What is the normal annual change in ocean pH (and temperature) for every year in between Ice Ages? (HINT: they have no data for any of it) I'll give you 1,000,000:1 odds they can't tell you that, or where we are between them. All they know is that IT'S MAN'S FAULT! (and women likely have nothing to do with it.) Feh...
Nelson Hyde Chick
Climate change and its ill repercussions will be impossible to reverse as long as mankind is allowed to grow by billions more. Go anthropocene!!!
VincentWolf
So if the seafloor dissolves will the oceans pour into the mantle??. Jist kidding.
Aloysius
Yeah, it's not like Global Warming is our problem. Like they say, I'll be dead by then. It's our children's problem and our children's children problem. Who cares, right? /s
YuraG
If I were to suggest my own math in order to take on the subject, I would first read the whole article on pnas.org rather than these well-written bullets. I wonder if those commenters who shared their numbers have read the original source and completely.
Catweazle
"Excess carbon dioxide isn't just building up in the atmosphere – the oceans are holding onto more of the stuff too, fizzing them up like soda." How curious. Only yesterday there was a climate change article that was using the DECREASE in dissolved CO2 and O2 in the oceans caused by the rising temperature to make some apocalyptic prediction about us being doomed due to something or other... I wish these scientists would make their minds up!
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