Invisible barrier on ocean surface reduces carbon uptake by half

May 29, 2018, Newcastle University
Credit: Newcastle University

An invisible layer of biological compounds on the sea surface reduces the rate at which carbon dioxide gas moves between the atmosphere and the oceans, scientists have reported.

Surfactants are organic compounds produced by marine plankton and bacteria that form an oily film on the surface of the water.

Publishing their findings today in the journal Nature Geoscience, scientists from Newcastle, Heriot-Watt and Exeter universities say the findings have major implications for predicting our future climate.

The world's oceans currently absorb around a quarter of all anthropogenic emissions, making them the largest long-term sink of carbon on Earth.

Atmosphere- gas exchange is controlled by turbulence at the , the main cause of which is waves generated by wind. Greater turbulence means increased gas exchange and, until now, it was difficult to calculate the effect of biological surfactants on this exchange.

The Natural Environment Research Council (NERC), Leverhulme Trust and European Space Agency funded team developed a novel experimental system that directly compares "the effect" between different sea waters collected along oceanographic cruises, in real time.

Using this and satellite observations the team then found that surfactants can reduce carbon dioxide exchange by up to 50 percent.

Predicting future global climate

Professor Rob Upstill-Goddard, professor of marine biogeochemistry at Newcastle University, said:

"These latest results build on our previous findings that, contrary to conventional wisdom, large sea surface enrichments of natural surfactants counter the effects of high winds.

"The suppression of carbon dioxide uptake across the ocean basin due to surfactants, as revealed by our work, implies slower removal of anthropogenic carbon dioxide from the atmosphere and thus has implications for predicting future global climate."

"As surface temperatures rise, so too do surfactants, which is why this is such a critical finding," adds Dr Ryan Pereira, a Lyell Research Fellow at Heriot-Watt University in Edinburgh.

"The warmer the ocean surface gets, the more surfactants we can expect, and an even greater reduction in gas exchange. 

"What we discovered at 13 sites across the Atlantic Ocean is that biological surfactants suppress the rate of gas exchange caused by the wind. We made unique measurements of gas transfer using a purpose-built tank that could measure the relative exchange of gases impacted only by surfactants present at these sites.

"These natural surfactants aren't necessarily visible like an oil slick, or a foam, and they are even difficult to identify from the satellites monitoring our ocean's surface. 

"We need to be able to measure and identify the organic matter on the surface microlayer of the ocean so that we can reliably estimate rates of gas exchange of climate active gases, such as carbon dioxide and methane."

Using satellite data to monitor ocean
The University of Exeter team, Drs Jamie Shutler and Ian Ashton, led the satellite component of the work. Dr Ashton said: "Combining this new research with a wealth of satellite data available allows us to consider the effect of surfactants on gas exchange across the entire Atlantic Ocean, helping us to monitor dioxide on a global scale."

The team collected samples across the Atlantic Ocean in 2014, during a NERC study on the Atlantic Meridional Transect (AMT). Each year the AMT cruise undertakes biological, chemical and physical oceanographic research between the UK and the Falkland Islands, South Africa or Chile, a distance of up to 13,500km, to study the health and function of our oceans.

The research cruise crosses a range of ecosystems from sub-polar to tropical and from coastal and shelf seas and upwelling systems to oligotrophic mid-ocean gyres.

Explore further: A switch in ocean circulation that helped end the Ice Age

More information: Ryan Pereira et al. Reduced air–sea CO2 exchange in the Atlantic Ocean due to biological surfactants, Nature Geoscience (2018). DOI: 10.1038/s41561-018-0136-2

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8 comments

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rileyss10
5 / 5 (1) May 29, 2018
This is probably too simplistic, but is this a possible good thing given that the only way we can reduce atmospheric carbon levels back to pre industrial levels is by carbon sequestration? It would be easier to remove from the atmosphere than from the ocean. Of course the easiest thing is to not create it in the first place, but it's past time for that.
JongDan
1.6 / 5 (7) May 29, 2018
@rileyss10
The question is, do we even want to reduce CO₂? Increased levels mean accelerated photosynthesis and as a result also higher possible agricultural yields. https://phys.org/...ury.html
Shootist
1.6 / 5 (7) May 30, 2018
This is probably too simplistic, but is this a possible good thing given that the only way we can reduce atmospheric carbon levels back to pre industrial levels is by carbon sequestration?


if you're worried, plant trees. Tell your mouthpieces to stop flying jet planes. Personally, I worry more about glaciation than co2.
PTTG
3.8 / 5 (4) May 30, 2018
JongDan, that's a lie. Shootist, you're an asshole, a liar, and a propagandist. Go to hell.
leetennant
5 / 5 (2) May 30, 2018
This is probably too simplistic, but is this a possible good thing given that the only way we can reduce atmospheric carbon levels back to pre industrial levels is by carbon sequestration? It would be easier to remove from the atmosphere than from the ocean. Of course the easiest thing is to not create it in the first place, but it's past time for that.


Volume is the biggest issue here. Although I think there's interesting work to be done in the area of seaweed farming, especially since a lot of seaweed types can be eaten. Seaweed farming could sequester CO2 and provide a more sustainable means of feeding people - assuming we could find a way to harvest it without releasing the sequestered CO2.
antialias_physorg
4.3 / 5 (6) May 30, 2018
The question is, do we even want to reduce CO₂? Increased levels mean accelerated photosynthesis

No. Photosynthesis is not driven solely by CO2 content but also requires nitrogen (from the soil, not the air) and water. The latter two are limiting factors. Rising CO2 and rising heat also mean that there is more evaporation...which means plants will require more water just to retain the status quo in photosynthesis.That means where water is the limiting factor plant growth will decrease.

You can achieve greater plant growth in a greenhouse if you add CO2 because there you can also add nitrogen and water to the soil at will. In the wild that doesn't work (unless you feel like starting a campaign to dump gigatonnes of nitrogen and water into rainforests. But I'm pretty sure that will cost a fair bit of cash)

In any case even the most ludicrously optimistic 'greening' effect will top out and then you're back to square one with a MUCH larger CO2 problem to deal with.
leetennant
5 / 5 (2) May 30, 2018
Oh @antialias_physorg... the same people who argue that the greenhouse effect isn't a problem because "the Earth is not a greenhouse" then decide it *is* a greenhouse when they're arguing why it isn't a problem on another issue.

The Earth is not a greenhouse. So you can't look at one to make decisions on how plants will respond globally to increasing CO2 levels.
granville583762
3 / 5 (4) May 31, 2018
We are observing biological phenomena of algae living on the surface of the sea where we have lost our senses, taking one compound that is part of the sea and atmosphere and has been for 4.5billion years a dooms day scenario of calamites proportions which without we would not exist! - may be that is the dooms day scenario of calamites proportions is that we do exist!

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