Seeding oceans with iron may not confer promised climate benefits

May 15, 2014
Seeding oceans with iron may not confer promised climate benefits
Ocean fertilisation.

Adding iron to the Southern Ocean may not have the climate benefits that advocates of geoengineering have hoped for, a new study suggests.

The theory is to fertilise plankton so they absorb more carbon from the atmosphere and thereby slow down climate change. But researchers found that natural patterns mean most of the carbon probably wouldn't stay put for long enough for a significant effect on the climate.

Simulations show that even if this method succeeds in absorbing carbon from the atmosphere and sinking it a kilometre beneath the Antarctic waters, currents may mean it only stays there for a few decades.

'This adds to the evidence that iron fertilisation is never going to be the one solution to the problem of climate change, though there are still a few places it could be useful,' says Josie Robinson, a PhD student at the University of Southampton and National Oceanography Centre and lead author of the paper, which appears in Geophysical Research Letters. 'Even if all the problems that have already been pointed out with it were somehow solved, we've shown that ocean circulation will limit any benefits.'

Robinson and her co-authors used a high-resolution 3D model of ocean circulation to simulate the movement of carbon that had been added to the Southern Ocean around Antarctica over the course of a century. By the end of that time, two thirds of the carbon had returned to the surface - on average, it took just under 38 years, far less than would be needed for any real effect on the climate.

So-called ocean iron fertilisation (OIF) has been seen as a strong candidate for geoengineering - modifying some aspect of the land, ocean or atmosphere to soften the blow of global warming. It would involve feeding iron into parts of the ocean where its absence is the major factor limiting plankton growth – that is, where other vital nutrients are plentiful but iron is scarce.

This video is not supported by your browser at this time.
Video showing the movement of the particles by which the carbon from iron fertilisation were represented using the oceanographic model. Each dot represents one particle; its colour represents its depth underwater.

Filling this gap could create huge blooms of plankton as these tiny marine plants feast on the sudden banquet, absorbing large amounts of carbon from the air. When the plankton die, would-be-geoengineers hope this carbon will sink down with their bodies and be trapped for millennia in the mud of the seabed, where it can't affect the climate. The Southern Ocean is one of the biggest iron-deficient areas on Earth, so it's been a popular candidate for iron fertilisation.

The idea seems plausible, but scientists have increasingly been asking tough questions. Some have pointed out that much of the carbon absorbed by the plankton won't make it to the seabed; instead, it will decompose on the way down and come right back to the surface to be released to the atmosphere.

The new study goes one step further by looking at the problem from the perspective of a physical oceanographer rather than a marine biologist or biogeochemist. They started out from the assumption that these problems have been solved, so that carbon from a plankton bloom has somehow got down to a kilometre beneath the surface; they then asked how long it would stay there.

'Other studies have looked at ocean circulation alongside marine biology, interactions between the sea surface and the atmosphere, and lots of other things,' says Robinson. 'We just concentrated on the ocean circulation, which meant we could use a much higher-resolution model than they could, and that gives us a much better understanding of how carbon would behave after reaching the deep ocean.'

It turns out that some of the very factors that make the Southern Ocean an attractive target for iron fertilisation also mean this probably wouldn't have much lasting benefit. Water that's rich in nutrients other than iron wells up here from the deep sea to the surface, and it's this that means only need a little iron to form large blooms. But these upwelling currents also pump deep carbon back into shallow waters where it can escape into the air.

Robinson says the research shows the importance of considering ocean circulation in assessing these kinds of proposal. 'A lot of the discussion has centred on the Southern Ocean, but from a physical oceanographer's point of view it's about the worst possible place to hide carbon,' she comments.

She adds that although the case for iron fertilisation in the Southern Ocean is weakened, the technique may still have some possibilities elsewhere - for example, the north Pacific is one potential target, with iron-poor waters and much less upwelling of water from the ocean depths.

An alternative option may be to move away from the idea of fertilisation with iron, focusing instead on adding other elements such as nitrogen or phosphorus to nutrient-poor waters where there's very little upwelling and so a much better chance of keeping down for long enough to have a significant effect on the climate. This could be more expensive than adding , but then letting run rampant wouldn't be cost-free either.

Explore further: Southern Ocean iron cycle gives new insight into climate change

More information: "How deep is deep enough? Ocean iron fertilization and carbon sequestration in the Southern Ocean." J. Robinson, E. E. Popova, A. Yool, M. Srokosz, R. S. Lampitt and J. R. Blundell. Geophysical Research Letters, Volume 41, Issue 7, pages 2489-2495, 16 April 2014. DOI: 10.1002/2013GL058799

add to favorites email to friend print save as pdf

Related Stories

The fate of bioavailable iron in Antarctic coastal seas

Dec 13, 2013

Science is exploring many options for carbon dioxide sequestration in order to mitigate the climatological impact of CO2. One of these is geoengineering: deliberate, large-scale intervention in the Earth's ...

Recommended for you

Kiribati leader visits Arctic on climate mission

Sep 20, 2014

Fearing that his Pacific island nation could be swallowed by a rising ocean, the president of Kiribati says a visit to the melting Arctic has helped him appreciate the scale of the threat.

NASA catches a weaker Edouard, headed toward Azores

Sep 19, 2014

NASA's Aqua satellite passed over the Atlantic Ocean and captured a picture of Tropical Storm Edouard as it continues to weaken. The National Hurricane Center expects Edouard to affect the western Azores ...

User comments : 18

Adjust slider to filter visible comments by rank

Display comments: newest first

verkle
1.9 / 5 (14) May 15, 2014
Whatever man tries to do to reign in "climate change"----it will all be futile. Or, could make things worse.

Climate Religion (beholding climate as a god, and making it one of our top priorities) might as well be killed off before it progresses any further.
Waaalt
3.8 / 5 (5) May 15, 2014
Somehow, the science press has plenty of time to ridicule geoengineering, but can't be bothered to make protecting the best carbon sinks above sea level a priority.

Here is practical geoengineering: plant some trees. Better yet, stop cutting them down where they matter most: equatorial forests/jungles in Brazil, Africa, and Indonesia. Then let and help them recover.

I can't and should not take any sort of carbon policy or 'climate change' related agenda seriously until it is willing to make the protection of equatorial, tropical jungles etc the very first priority.

If humanity literally used no fossil fuels whatsoever, but still burnt down the equatorial biomes so they could be turned into farmland, then all the dire predictions would have to stay about the same anyway.

Restoring equatorial biomes is better than not, but mostly too late: burning them down releases 500+ years of stored carbon, while reducing the total capacity of the biosphere to fix carbon.
Shootist
1 / 5 (3) May 15, 2014
Whatever man tries to do to reign in "climate change"----it will all be futile. Or, could make things worse.


bloody nonsense.

If carbon mitigation becomes necessary (unlikely according to Dyson), the planting of fast growing plants will occur. Problem solved.

This issue is driven at least partly by those who believe the State should control the means of production.

PinkElephant
4.2 / 5 (5) May 15, 2014
@Shootist,

"No balloon and no aeroplane will ever be practically successful."

-William Thomson, 1st Baron Kelvin

If you *have to* pick a genius scientist as your contrarian idol, a towering giant of Lord Kelvin's stature beats the pants off dinky wee Freeman Dyson.

... just sayin'
alfie_null
5 / 5 (3) May 16, 2014
Whatever man tries to do to reign in "climate change"----it will all be futile. Or, could make things worse.

Y'know, that pretty much sums up anything new we try. I'm real glad the likes of you aren't in charge of things. We'd all still be living in caves, living short nasty lives, probably dying painfully, and in general not knowing squat about anything.
antialias_physorg
5 / 5 (1) May 16, 2014
Here is practical geoengineering:

Here's a practical geoengineering approach: Get some reflective screens into space. They don't need to be overly large.

And the advantage (as opposed to ALL other geoengineering approaches) is that you can turn them off pretty much instantly when not needed (or if they should have some unwanted side effect)

Dumping gunk into the oceans certainly doesn't sound like a 'no side-effects guarateed'-scenario to me. Pretty much the opposite.

And we have NO way to clean it up if stuff goes haywire. None whatsoever.
Agomemnon
1 / 5 (2) May 16, 2014
Here is practical geoengineering:

Here's a practical geoengineering approach: Get some reflective screens into space. They don't need to be overly large.


What is wrong with you people!! CO2 is not a problem. Too little CO2 is a problem. If you cut our current CO2 concentration in half you will kill all plant life on earth.

The current giant elephant in the room that is harming the planet isn't CO2 its things like Glyphosate which is an endrocrine disrupting, cancer causing, patented-antibiotic that is in the rain, soil, and tissue of every man woman and child in Western civilization.
antialias_physorg
5 / 5 (1) May 16, 2014
If you cut our current CO2 concentration in half you will kill all plant life on earth.

Erm..how about: no? Where do you get that idea?

Agomemnon
1 / 5 (2) May 16, 2014
If you cut our current CO2 concentration in half you will kill all plant life on earth.

Erm..how about: no? Where do you get that idea?


facts of minimal requirements for plant life to exist. You know...science.
PinkElephant
5 / 5 (3) May 16, 2014
@Agomemnon,
CO2 is not a problem.
How, in your *expert* judgement, is it not a problem?
If you cut our current CO2 concentration in half you will kill all plant life on earth.
Current concentration is ~400 ppm. Half of that is 200 ppm. It's been at that level numerous times in even not-too-ancient history:

http://www1.ncdc....tion.gif

Oddly, Earth plant life is still around...
its things like Glyphosate which is an endrocrine disrupting, cancer causing, patented-antibiotic that is in the rain, soil, and tissue of every man woman and child in Western civilization
Just because various synthetic chemical pollution is a problem, doesn't preclude excess CO2 from being a problem. You're employing a false dichotomy. Also Glyphosate is a pesticide, not an antibiotic. That's not to say excessive (ab)use of antibiotics isn't a problem. But again, all of these are not mutually exclusive issues.
Agomemnon
1 / 5 (2) May 17, 2014
.
its things like Glyphosate which is an endrocrine disrupting, cancer causing, patented-antibiotic that is in the rain, soil, and tissue of every man woman and child in Western civilization
Just because various synthetic chemical pollution is a problem, doesn't preclude excess CO2 from being a problem. You're employing a false dichotomy. Also Glyphosate is a pesticide, not an antibiotic. That's not to say excessive (ab)use of antibiotics isn't a problem. But again, all of these are not mutually exclusive issues.
I am not applying a false dichotomy. I'm pointing out a real problem with real immediate hazards (glyphosate). Which is an herbicide, not a pesticide like you said, and is a patented antibiotic. I didn't patent it Monsanto did.
You, on the other hand, are attributing magical and non-scientific properties to CO2. Plant asphysxiation due to lack of CO2 is between .02% and .016% (depending on species). Plants evolved with several times the CO2 we currenlty have.
PinkElephant
5 / 5 (2) May 17, 2014
@Agomemnon,

I apologize, when I said pesticide I indeed meant herbicide. But then weeds are a kind of pest aren't they.

Anyway an antibiotic is something that specifically targets bacteria. Antibiotic is a synonym for antibacterial.

As for 'magical' or 'unscientific' CO2 properties, I suggest you at least find the global warming article on Wikipedia and familiarise yourself with the bare fundamentals of this SCIENCE in lieu of continuing to spout sheer inanities. Cheers.
Agomemnon
1 / 5 (1) May 18, 2014
@PinkElephant
I said glyphosate (Roundup) is an antibiotic (you know the kind the CDC is warning against overuse because of supergerms being created by said antibiotics) because it is. Monsanto has a patent on glyphosate as an antibiotic. That is a real danger, not CO2.

I know the global warming theory well. It's the catastrophic crisis global warming that is obviously nonesense. For one even as CO2 has increased there has been no global warming for 18 years. I'm of course referring to empirically measured values from satellites. I know the value and effect of CO2 as a greenhouse gas, which is why I discounted the crisis theory long ago.
PinkElephant
5 / 5 (2) May 19, 2014
Monsanto has a patent on glyphosate as an antibiotic.
Only half-true. Glyphosate acts as an 'antibiotic' only in combination with certain 'adjuvants'. By itself, it is quite ineffective as an antibiotic, and is readily metabolized by soil bacteria. Glyphosate's primary identification is as an herbicide; its weak antibacterial properties are more of a side-effect.
It's the catastrophic crisis global warming that is obviously nonesense.
Well, you must be a towering *genius* indeed, if it's so obvious to you and yet so not obvious to the rest of the scientific community. Or, you are full of crap. Perhaps the latter is more likely...
For one even as CO2 has increased there has been no global warming for 18 years.
Wrong. See these:
http://static.ber...pped.pdf
http://www.nodc.n...CONTENT/
I know the value and effect of CO2 as a greenhouse gas
You obviously do not. You are ignorant of the physics involved.
Agomemnon
1 / 5 (1) May 19, 2014
@PinkElephant,
See this is what I keep talking about. Real crisis issues are ignored (Glyphosate) and false crisis (catastrophic global warming) is paid attention to.

First: Glyphosate does not readily metabolize you Mansanto apologist. Glyphosate is in rain and water supply and found in the breast milk of mothers across the country. It bioaccumulates in human tissue as well as animals that are fed this crap. The EPA, fraud organization that it is, keeps increasing by thousands of percent its allowable amount of this poison. But CO2, which is non-toxic plant food, they are all concerned about. Nonesense.

PinkElephant
5 / 5 (2) May 19, 2014
I do not apologize for Monsanto. Humans and animals are not bacteria. I *agree* with you that Glyphosate is a problem, you dimwit... And, I can both walk and chew bubblegum at the same time - we can be addressing both CO2 and other pollutants. Pollution controls are not mutually exclusive.
Agomemnon
1 / 5 (1) May 19, 2014
You cannot address CO2 that will reduce its concentration in the atmosphere. Its not a problem anyway. You cannot prove CO2 is a problem (especially when its a net positive good) at least in any scientific way.
You are selling a belief system via a narrative. Not scientific proof.
What is your proposal what would actually work? Anything?
That's what I thought.
PinkElephant
5 / 5 (2) May 19, 2014
Natural removal of excess CO2 from the atmosphere is a process that takes many centuries, even if we abruptly stopped adding yet more CO2 into the system. It's far slower in action than the GW effect of that excess CO2.

As for solutions, it's pointless discussing them with someone who refuses to acknowledge the very existence of the problem in the first place.

And physics has long since proven that excess CO2 is a problem. That you are ignorant of the math and data involved (and seemingly smug and proud about your ignorance - as if it were some badge of honor - well, maybe among the secret moron society, but I digress), doesn't make any of it go away. All it produces is a picture of you standing bent over, with your head buried deep in the ground.