Environment

The ocean's crucial carbon capture mechanism is slowing down

The ocean's crucial carbon cap...
Photosynthesizing plankton help capture carbon from the atmosphere, but warming temperatures are slowing down the process
Photosynthesizing plankton help capture carbon from the atmosphere, but warming temperatures are slowing down the process
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Photosynthesizing plankton help capture carbon from the atmosphere, but warming temperatures are slowing down the process
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Photosynthesizing plankton help capture carbon from the atmosphere, but warming temperatures are slowing down the process

The Earth is actively fighting back against human-induced climate change. Some of the excess carbon dioxide we're pumping into the air is absorbed by "carbon sinks" like forests and oceans, which helps to slow down – but not stop – the greenhouse effect. Unfortunately, a new study has found that oceans are gradually becoming less effective carbon sinks, thanks to rising global temperatures.

Photosynthesizing organisms do most of the heavy lifting when it comes to bailing CO2 out of the air. Forests have stepped up their game in recent years, absorbing more greenhouse gases than usual and helping slow the rise of atmospheric CO2 levels. Meanwhile, plankton at the sea surface are gobbling up carbon in the water, and as they die, they drag it down to the depths of the ocean at a rate of about 6 billion tons a year.

But a study from MIT has found that warming of the waters is slowing down this natural sponging process. That's because photosynthesizing organisms flourish or flounder depending on the water temperatures – and so do respirers, creatures like bacteria and krill that absorb oxygen and release carbon dioxide. While photosynthesizers grow and die faster in colder waters, respirers are more active when it's warmer.

The delicate dance between these two competing yet symbiotic types of organism greatly affects how well the oceans perform as a carbon sink. The team developed a model to measure the "export efficiency" – the rate at which carbon is absorbed into the deep – at different temperatures, centered around the interplay between photosynthesizers and respirers.

"We had a simple way to describe how we think temperature influences export efficiency, based on this fundamental metabolic theory," says B.B. Cael, first author of the study. "Now, can we use that to see how export efficiency has changed over the time period where we have good temperature records? That's how we can estimate whether export efficiency is changing as a result of climate change."

To do so, the researchers gathered temperature data from three different sources, taken every month between 1982 and 2014 and reporting on locations all over the world. Then, they fed that information into their model to estimate the average export efficiency for the planet's oceans every month, and tracked how that changed over time.

Over those 33 years, water temperatures increased at the ocean surface, while the export efficiency decreased by between 1 and 2 percent. That might not sound like a whole lot, but it equates to an extra 100 million tons of plankton remaining near the surface every year.

"We figured the amount of carbon that is not sinking out as a result of global temperature change is similar to the total amount of carbon emissions that the United Kingdom pumps into the atmosphere each year," says Cael. "If carbon is just standing in the surface ocean, it's easier for it to end up back in the atmosphere."

The team says the model has the potential to be used to predict how effective the ocean will be as a carbon sink in the future, but it won't be as reliable thanks to uncertain temperature projections.

The study was published in the journal Limnology and Oceanography.

Source: MIT

6 comments
Rumata
MIT guys are totally wrong with thir idea. The atmospheric CO2-level is determined by the temperature dependent equilibrum between solved CO2 in the oceans and the gaseous CO2 in the air. Actually, the oceans store 50 times more CO2 than the atmosphere. Hence, in the current equilibrum, the 98% of the human CO2 emission is sucked up by the oceans, and only 2% of it will remain in the air, regardless of the amount of human emission. And because currently the human CO2 emission is ~5ppm/year (relative to the volume of the atmosphere), the human emission can only increase the atmospheric CO2-level only by 0,1ppm/year, hich is undetectable. So, the actual change in the amount of CO2 sucked by the oceans comes only from temperature variations, that change the equilibrum. Hence, there is no "sponge effect" at all. There is only temperature-dependent equilibrum. Global temperature determines the atmospheric CO2 level. - So, it is true, that photsythesis or fossil fuel burning can change the atmospheric CO2 level. But because of the huge storage capacity and huge CO2 reserve of oceans, photosynthesis or fossil fuel burning can only change it very slow. For examle, with the current 5ppm/year human emission, we would need 1000 years to increase the atmospheric CO2 level by 100ppm. And the effects of photosysthesis can be even slower. Hence, nobody can really measure the "sponge effect" of photosysthesis, because for short (<1000 year) terms, the effect of global temperature changes on equilibrum CO2 level are much stronger than that.
Hugh Rose
This is fantasy land reporting. Thank you Rumata for your comment. C02 is plant food and any warming/increase in plant food is good for anyone trying to grow foodstuffs. The current level of 403 ppm it is quite literally a drop in the ocean!
Anne Ominous
I will only say that I'd take this study with a huge grain of salt.
If all the alarming news of the last 15 years had turned out to be true, we would all have been dead long ago.
chase
I was touted by some as one of the top ten SW Aquarist in the world at one time not too long ago. Which i guess means i know a thing or two about contained reef systems. ie saltwater systems. The ocean just a bigger containment of saltwater. And it wasn't that i was a grand scientist. Or oceanographer that made me so good at what i did. To me it was simple. It came naturally to me. And yes i studied my ass off. Point is, and yes there's a point to this. Sometimes you don't need to be an MIT grad to recognize change. To realize there's a problem. The new "fad" of propaganda.. which is all propaganda is, a fad. And truer to the term than global warming will ever will be. Is to deny what has been recognized as change, and is a major problem. Why have a new "fad" of deniability propaganda? The answer is quite simple. Money. And Power. Fear of the loss, or desire of gain of either.
The science has been done. And by those that know and have access to more first hand information than anyone that's going to post on the comments here. Including me. It's been done many times over by scientist all over the world. And all recognize and agree with the findings.
Again... We don't really need to be a scientist to see something is happening. That change in nature is coming about at a very fast rate.
You want to say humans had nothing to do with it? Fine. Personally, i think you'd have to be a complete moron not to recognize the human impact on the planet. Some impact so bad you'll die in a very short order if you go visit certain areas that have been so damaged by human interaction. Waters that'll kill you by the time you finish the drinking a glass of it, again due to human interaction.
Be that as it may. There is a major change coming. Be out an ice age or what ever. Current CO2 levels beyond anything seen before. Who caused it.. let's toss that out the window for a moment. The fact is, adding to it is a bad thing. As humans we add too much. To much of a lot of things. And that needs to change. The Earth is a container, a confined space. Just a bigger one than an aquarium. But the principal for curing problems or things that get out of balance the same. If levels are too high, you have to lower them. If too low, you raise them. Balance is fragile. The smaller the confined space, the more critical it becomes. The Earth is out of balance. It will try to correct balance on its own. The father it goes out of balance the harsher the corrective measures. When nature tried to correct balance.. all kinds of crazy shit happens. Things get wacky as it attempts to re-establish balance. That's all that science is really trying to warn everyone about. How many times have people shown the world that fracking caused their water to be able to be lit on fire coming out of the faucet? Certainly more than once. How many times did the gas companies deny fracking had anything to do with it? And spread a "fad" of propaganda of denial. "Oh the water was like that" "Oh it's safe to drink!" Etc etc. You can join in the the current fad of denial... But keep in mind. If you're posting a comment on this. You just may be still alive to eat those words when nature comes a calling to balance the books. And nature.. well she don't care who's at fault, nor about profit and loss statements. I hope I'm here for it when it comes. When the ocean flicks the switch so to speak. It should prove interesting to say the least. Cheers...
Tjoe
My state has 23,000,000 acres of which 95% was covered by hardwood forests about 250 years ago. In 1920 it reached a low of under 15% with forest. Today it's around 20% with marginal lands reverting to (un-managed) forestland.
That's 17,000,000 fewer acres growing deciduous trees (just in one state)... a huge carbon sink that now grows corn and beans for about 3 months a year and is raw earth for 9. Funny that Paris didn't mention midwest US de-forestation.
Douglas Bennett Rogers
Desert irrigation and other evaporation has about five times the effect of human CO2. It would be a lot cheaper to reduce pumped desert water by 20% than to shut down fossil fuel burning. Another issue is direct reflectivity. An easy way to increase this is desertification. This happens on its own as a response to global warming.