What . . . About Geoengineering . . . Part IV: Shall We OIF?


If you’re puzzled by the question in the title because you don’t know what “OIF” means, please stand by. An explanation is forthcoming. But, first, I think I should mention that the growing concentration of carbon dioxide in the atmosphere is making the ocean more acidic.[1] As a result, species that depend on calcification, such as corals, mollusks, and even some types of algae, are being affected. And when they suffer, species up the food chain suffer, too. According to biologists who made a case study of Tatoosh Island, just off the northwest corner of Washington state, populations of gulls and murres declined 50 percent over a decade due, the researchers suspect, to the damage inflicted on their food supply by increased ocean acidity.[2] Fisherman and scientists in Alaska worry about the impact of “corrosive waters” on halibut, salmon, and smelt.[3]

Given that oceans cover 70 percent of the planet, the fact that CO2 is acidifying the world’s oceans is a very big deal. So geoengineers have come up with a few ideas for making the water less acidic. One of them, known as ocean iron fertilization (or OIF, for short), involves dumping tons of iron into the sea.

Why OIF-up the ocean? Well, because lush blooms of algae could grow in some parts of the ocean where they don’t grow now—if only the water contained more of the essential nutrient iron. And more algae might be helpful because, while alive, the little green organisms would absorb carbon dioxide from the air, and then, when they passed away, their itty-bitty bodies would sink to the ocean floor, taking the absorbed carbon with them. Once the algae carried the carbon to the bottom of the sea, it would remain locked up there indefinitely. So, if more iron in the water would mean more algae, and more algae would mean less atmospheric CO2, and less atmospheric CO2 would mean less global warming, then why not dump a little iron in the water? That’s the question a group of scientists pondered, anyway.

So they donned their lab coats and got to work. In beaker experiments, they found that for every one part of iron they added, algae sequestered 100,000 parts of carbon.[4] Based on those encouraging laboratory results, groups of geoengineering scientists took to the sea to conduct field experiments. A 1995 iron sprinkling of the equatorial Pacific reportedly turned “[c]rystal-clear blue water . . . green overnight as plankton bloomed by the ton.” Recalling the experience for a reporter, Canadian oceanographer Bill Cochian gushed, “It was almost frightening the change was so massive!” According to Cochian, in the wake of the half-metric-ton iron dump, the algae population increased thirty-fold and sucked nearly 2,500 metric tons of CO2 from the air.[5]

Twelve years later, scientists who gathered for an ocean-iron-fertilization conference at the Woods Hole Oceanographic Institution reported far less impressive results, however. In each of twelve separate experiments (six in the Southern Ocean, four in the northwest Pacific, and two in the equatorial Pacific), the algae population did multiply rapidly after the introduction of iron. In some cases, the surface waters’ chlorophyll content (which scientists use as a proxy for algae because it is easier to measure than individual algae are to count) increased as much as fifteen-fold. Unfortunately, however, “[o]nly a tiny fraction of the carbon drawn down by blooms [sunk] from the surface into deeper waters.” According to Philip Boyd, of the New Zealand National Institute for Water and Atmospheric Research, approximately 200 tons of carbon were sequestered for every one ton of iron added to the water, and although that sounds pretty good, it’s “a far cry from early experiments in laboratory beakers that yielded estimates around 100,000 to 1.” Scientists believed their results might have been better if their budgets had allowed them to monitor the ocean at deeper levels and for longer periods. But even though their results were a bit disappointing, the scientists’ consensus at the 2007 conference was “that iron fertilization does in principle work well enough to squirrel away carbon for at least a few decades—possibly useful in the world’s efforts to solve its carbon emissions problem.”[6]

So, ocean iron fertilization seems to have several things going for it. For one thing, it’s simple. It requires little but knowing the best parts of the ocean to fertilize, sailing there, and then tossing the iron into the drink. For another thing, as elements go, iron is cheap. According to Stuart Sim, author of The Carbon Footprint Wars, an investment of around $100 billion in ocean iron fertilization would enable enough algae to grow to make a significant difference in atmospheric CO2.[7] And for yet another thing, unlike the various solar-radiation-management proposals discussed in earlier posts, ocean iron fertilization would combat acidification of the ocean. Before carbon dioxide ever had the chance to make the ocean acidic, our little, green algal friends would suck it right out of the air. (You go, greens!)

Are you, perchance, now waiting for the other shoe to drop? If so, you won’t be disappointed because as you anticipated, I am going to tell you why ocean iron fertilization might not be such a great idea.

But not until the next post. So please check in tomorrow (or as soon as you can) for “What You Always Wanted to Know About Geoengineering but Were Afraid to Ask, Part V.”


[1] Lovejoy, Thomas E. “Geo-Engineering Can Help Save the Planet.” New York Times. June 10, 2011.

[2] Solie, Stacey. “Scientists Adopt Tiny Island as a Warming Bellwether.” New York Times. October 6, 2012.

[3] Eilperin, Juliet. “Ocean Acidification Emerges as New Climate Threat.” Washington Post. September 30, 2012.

[4] Powell, Hugh. “Will Ocean Iron Fertilization Work?” Oceanus. Woods Hole Oceanographic Institution. January 7, 2008. http://www.whoi.edu/oceanus/viewArticle.do?id=35609

[5] “Large Dose of Iron Revitalizes Lifeless Expanse of Ocean.” Associated Press. Eugene Register-Guard. October 4, 1996, p. 7B.

[6] Powell, Hugh. “Will Ocean Iron Fertilization Work?”

[7] Sim, Stuart. 2009. The Carbon Footprint Wars: What Might Happen If We Retreat From Globalization? Edinburgh, UK: Edinburgh University Press, p. 106.






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