April 19, 2004
Iron Enriching Southern Ocean Pulls Carbon Dioxide From Atmosphere

Salting the Southern Ocean with iron results in increased growth of phytoplankton that take carbon dioxide from the atmosphere and extract the carbon into a form that eventually sinks deep into the ocean.

A remarkable expedition to the waters of Antarctica reveals that iron supply to the Southern Ocean may have controlled Earth's climate during past ice ages. A multi-institutional group of scientists, led by Dr. Kenneth Coale of Moss Landing Marine Laboratories (MLML) and Dr. Ken Johnson of the Monterey Bay Aquarium Research Institute (MBARI), fertilized two key areas of the Southern Ocean with trace amounts of iron. Their goal was to observe the growth and fate of microscopic marine plants (phytoplankton) under iron-enriched conditions, which are thought to have occurred in the Southern Ocean during past ice ages. They report the results of these important field experiments (known as SOFeX, for Southern Ocean Iron Enrichment Experiments) in the April 16, 2004 issue of Science.

Previous studies have suggested that during the last four ice ages, the Southern Ocean had large phytoplankton populations and received large amounts of iron-rich dust, possibly blown out to sea from expanding desert areas. In order to simulate such ice-age conditions, the SOFeX scientists added iron to surface waters in two square patches, each 15 kilometers on a side, so that concentrations of this micronutrient reached about 50 parts per trillion. This concentration, though low by terrestrial standards, represented a 100-fold increase over ambient conditions, and triggered massive phytoplankton blooms at both locations. These blooms covered thousands of square kilometers, and were visible in satellite images of the area.

Each of these blooms consumed over 30,000 tons of carbon dioxide, an important greenhouse gas. Of particular interest to the scientists was whether this carbon dioxide would be returned to the atmosphere or would sink into deep waters as the phytoplankton died or were consumed by grazers. Observations by Dr. Ken Buesseler of Woods Hole Oceanographic Institution and Dr. Jim Bishop of Lawrence Berkeley National Laboratories (reported separately in the same issue of Science) indicate that much of the carbon sank to hundreds of meters below the surface. When extrapolated over large portions of the Southern Ocean, this finding suggests that iron fertilization could cause billions of tons of carbon to be removed from the atmosphere each year. Removal of this much carbon dioxide from the atmosphere could have helped cool the Earth during ice ages. Similarly, it has been suggested that humans might be able to slow global warming by removing carbon dioxide from the atmosphere through a massive ocean fertilization program.

This report provides support for the idea that dissolving large quantites of iron into the ocean could be used as a technique to slow or perhaps even reverse the build-up of carbon dioxide in the atmosphere. The report of the Woods Hole scientists is particularly interesting because it suggests that some of the carbon pulled from the atmosphere by ocean iron fertilization will stay out of the atmosphere for long enough to be worthwhile as an approach for preventing global warming.

Sequestered iron that falls deep in the oceans will stay out of the atmosphere for centuries. (same article here)

The controversial idea of fertilizing the ocean with iron to remove carbon dioxide from the atmosphere gained momentum in the 1980s. Climate and ocean scientists, as well as ocean entrepreneurs and venture capitalists, saw potential for a low-cost method for reducing greenhouse gases and possibly enhancing fisheries. Plankton take up carbon in surface waters during photosynthesis, creating a bloom that other animals feed upon. Carbon from the plankton is integrated into the waste products from these animals and other particles, and settles to the seafloor as "marine snow" in a process called the "biological pump." Iron added to the ocean surface increases the plankton production, so in theory fertilizing the ocean with iron would mean more carbon would be removed from surface waters to the deep ocean. Once in the deep ocean, the carbon would be "sequestered" or isolated in deep waters for centuries. The oceans already remove about one third of the carbon dioxide released each year due to human activities, so enhancing this ocean sink could in theory help control atmospheric carbon dioxide levels and thus regulate climate.

Cost estimates for removing carbon from the atmosphere using ocean iron fertilization are much lower than competing alternative mechanisms of sequestration.

However; estimates have been produced, suggesting only US$1-5 per tonne of carbon fixed. This compares very well with US$50-200 for other proposed sinks, so both commercial and political interest is thus high.

The range of cost estimates for removing carbon with ocean iron fertilization vary considerably.

A controversial report by the National Academy of Sciences in 1992 looked at iron fertilization, among other geoengineering options. Although the NAS noted some caveats, it concluded that iron fertilization does have one attractive feature: a relatively cheap price tag. Running 360 ships full-time to fertilize 46 million square kilometers of ocean would cost somewhere between $10 billion and $110 billion a year.

Additional work needs to be done to measure other possible effects of fertilization that might undermine the benefit of removing carbon from atmospheric carbon dioxide.

Understanding of the impact on greenhouse gas balances through ocean fertilisation by the addition of iron or nutrients, such as nitrates and phosphates, is still limited (Annex B). With regard to iron fertilisation, there are substantial uncertainties about the overall response of the Southern Ocean ecosystem, and it is possible fertilisation could lead to increased emissions of other greenhouse gases, nitrous oxide and methane, significantly offsetting any increased uptake of carbon dioxide. Estimated costs of ocean fertilisation are highly uncertain. One source estimates are £3 to £37/tC but this may be rather optimistic due to uncertainties over the effectiveness of the process. The other option, ocean fertilisation by nutrients appears to be even less practical than that for iron. Costs are also uncertain but are likely to be higher at £30 to £120/tC.

But those estimates will become more precise as additional research work more accurately measures how much of the carbon fixed by ocean plants ends up sinking into the ocean depths.

The ferilization of oceans with iron would need to be done continuously to maintain a continued rate of extraction of carbon from the atmosphere to counteract carbon dioxide emissions from fossil fuel burning. Cessation of seeding would very quickly lead to a return to lower levels of plankton.

Projections from this experiment indicate that if the polar oceans were completely seeded in such a fashion, atmospheric CO2 would decrease by about 10%. This would substantially mitigate the greenhouse effect caused by CO2. Such plankton growth has other benefits as well. One potential benefit may be that the increase in plankton would lead to an increase in the populations of other ocean fauna, such as whales and dolphins, that feed on plankton. Another benefit, again, is that it is relatively inexpensive. A continual iron-seeding program would cost only about $10 billion a year. Yet another benefit is that plankton growth stops about a week after seeding, so if the plankton were determined to have a detrimental effect, the effort could be quickly disbanded.

Most of the world's carbon (leaving aside deeply buried carbon) is already in the oceans.

But why store carbon in the oceans?
Faced with the stark reality, even the International Panel on Climate Change has admitted that we may have to consider what it calls ‘carbon management strategies’ to complement reductions in greenhouse gas emissions. One option is to store the excess carbon on land; this is already being done in deep geological formations, abandoned mines and the like.

But it is the oceans that have the greatest natural capacity to absorb and store carbon. On an annual basis, the surface of the ocean absorbs about 30% of the carbon in the atmosphere, less during El Niño years. But over very long timescales, of thousands of years, as much as 85% is absorbed by the oceans. The ocean contains an estimated 40,000 billion tons of carbon, as compared to 750 billion tons in the atmosphere and about 2200 billion tons on land. This means that, were we to take all the atmospheric CO2 and put it in the deep ocean, the concentration of CO2 in the ocean would change by less than 2%.

Iron ocean fertilization could be a bone for fish growth as the fish ate away at the much larger quantities of plankton. So part of the cost of this proposal might be paid for in larger fish catches. If a property rights system could be worked out for the fertilized ocean fisheries then a portion of the sales of harvested fish could go toward paying for the ocean fertilization. Though a carbon tax on all oil, natural gas, and coal extraction could be levied as well.

Share |      Randall Parker, 2004 April 19 12:53 AM  Engineering Environmental

Saul Nunez said at November 10, 2006 1:00 PM:

I read the article in the Science magazine when it came out. I thought it was a great finding. But, what has happened since then? Has any country taken interest in fertilizing the ocean waters with iron? I hope to hear from you.

Best regards,

Saul Nunez

ben said at February 2, 2007 5:47 AM:

Yes I am equally curious. Is this a viable option? Has any work be done to measure what the potential side effects might be?

Haven Schrecengost said at October 30, 2007 2:51 PM:

I want to be a part of this solution. Is there a reputable charity to donate to that is taking action.

Brett Clements said at February 16, 2008 4:10 PM:

The earth relies too heavily on the crude oil infrastructure to reduce carbon omissions, especially at a time when countries like China and India will be putting cars on the roads. This civilization has gone way too far down the petro-chemical road. The only way out of this mess is to remove carbon from the atmosphere. And remove it fast. Unfortunately, I'm not a scientist. Only a documentary film-maker, who is happy to contribute his talents to this discussion. The ocean is our air conditioner. Salting it with iron is a lot more doable than some of the other crazy ideas I've heard but we'd better get moving.

Don Libby said at March 9, 2008 12:04 PM:

Recent work on ocean fertilization and other geo-engineering options is summarized in the IPCC Fourth Assessment Report, Working Group III "Mitigation of Climate Change", Chapter 11 (downloadable from http://www.ipcc.ch/ipccreports/ar4-wg3.htm .) Basically it says more recent research on ocean fertilization shows earlier work over-estimated carbon sequestration potential and under-estimated the potential cost. It's not something to rush into. Fortunately, many other mitigation options are discussed in the report, many of which would actually make money (especially energy conservation). I think carbon capture and storage, as well as biomass energy with charcoal sequestration in soils, are the most likely techniques for removing CO2 from the atmosphere for the next several decades. Check out the International BioChar Initiative: http://www.biochar-international.org/home.html

alan said at June 24, 2008 12:52 AM:

I think this is a great idea. Not only does it offer the option of removing carbon dioxide from the atmosphere, the increase in marine life would offer an alternative food source for humans. More abundant and cheaper seafood can mean a diversion of our dietry protein intake away from red meat sourced from live stock, a known significant source of greenhouse gas in the form of methane. To compound this effect, less livestock would mean less agricultural land needed in the form of pastures, which can mean more land dedicated to the planting of trees and hence offer additional land based carbon sequestration. Having no expertise in this field myself, my only concern is regarding the fate of the carbon sequestered in the oceans: could it somehow return to the atmosphere detrimentally; and what are the bio-environmental and geological implication of extra carbon sequestration in the deep ocean.

I do no believe fiscal consideration should be considered in the discussion of possibly reversing global warming on two fronts: firstly because 'money' is an artificial concept and that the salvation of our planet and our own futures is being obstructed by something we have 'thought up' is simply ludicrous; and secondly because the potential cost associated with allowing climate change to continue on present course could easily outweigh any cost needed to halt or reverse this progression, and by that I refer to the costs of increasing natural disasters such as hurricanes and flash floods, the cost of aid to salvage and preserve human lives after disasters, the loss of lives and livelihoods and jobs that will lead to disruptions in affected industries, and then the indeterminable long term sequelae of increased health care costs, increased crime rates and generational propagation of low socioeconomic related problems in the affected populations.

That alternative and innovative alternatives must be considered such as this is without questions. Contemporary politics talk alot about reducing carbon emissions and offsetting it. Frankly I think carbon credit is the most retarded thing I've heard: first because if you refer to the above paragraph you'll see why because money is artificial, and secondly paying someone else so you can produce emissions is just defeating the whole principle of what you are trying to achieve in the first place. Reducing carbon emissions too I think is a ridiculous idea. Unless one goes about drilling/refining and stealing all the oil reserves from around the world, putting them into barrels and firing the entire stockpile into the space towards the Sun, there is no way to reduce carbon emissions. With the increasing population and urbanization in places such as China and India, there is going to be rising demands for fuel and cosumerism. This will only mean more cars, more trucks to deliver goods and produce, more factories to produce said cars, trucks and produce/product, hence more demand on fossil fuels, coal and eletricity.

Ari said at September 8, 2008 5:29 PM:

Seeding the ocean with iron or nitrogen fertilizers is a very short sighted and dangerous solution to our over consumption issues as a society. There is no way to tell the long term detrimental effects of adding more nutrients to the ocean. Just the posts on this website show that even people who are educated enough to look at Science and actually care about the environment have no idea about the basic affects increased nutrients have on marine ecosystems. If you don't know a lot about marine ecosystems its easy to assume that increasing phytoplankton will increase other organisms on higher trophic levels, but that is not the case. Anyone ever heard of eutrophication?? When primary producers are increased due to a deposition of more nutrients it upsets the balance of that ecosystem. Higher productivity of phytoplankton and algae limit the sunlight available to other organisms and drastically change the oxygen balance of the ecosystem.(Higher oxygen during the day due to increased photosynthesis and much lower at night due to increased organisms that require oxygen to live) This can cause dead zones where there is little to no available oxygen and larger animals such as fish and shrimp will die of suffocation.

Scientists do not even know if there is a direct correlation between increased iron and cooler temperatures or how to control this effect once it has begun. Plus it could lead to emission of other greenhouse gases, and death of entire underwater ecosystems! So if scientists aren't sure, then massive companies trying to make money off of scared citizens sure as hell don't know!

Everyone is always looking for quick fixes for our environmental problems. If we spent that much energy on cutting back emissions and developing renewables, we would already be on our way to healing the environment. But since even fixing the environment has now become big business, money will win again and we'll just keep letting corporations do the thinking for us. so sad.....

Michael Ejercito said at April 24, 2009 11:16 AM:

Cutting back emissions will create poverty and hardship.

Jason said at July 7, 2010 10:09 PM:

Not cutting back emissions will create the ultimate hardship. Forever.

Matt said at April 12, 2011 9:51 PM:

Ari this at least has to be tried, like you said no one knows the long term consequences, but im sure they can at least be predicted by trialing it. The artical states the benefits this could have on the ocean life... Surely the phytoplankton would not get so thick that seaweed and coral would not recieve sunlight, im sure if that was an occurance it would have been stated in the article? The whole food chain relies upon phytoplankton,therefore if this caused a drastic increase in sea life, we would counteract that by having a diet focused on seafood instead. Sea food of course having a much lower impact on the world than meat and poultry production.

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