380 Fertilizing the Ocean with Iron Is this a viable way to help reduce carbon dioxide levels in the atmosphere? 360 ive me half a tanker of iron, and I’ll give you an ice Twenty years on, Martin’s line is still viewed alternately age” may rank as the catchiest line ever uttered by a as a boast or a quip—an opportunity too good to pass up or a biogeochemist.“G The man responsible was the late John Martin, misguided remedy doomed to backfire. Yet over the same pe- former director of the Moss Landing Marine Laboratory, who riod, unrelenting increases in carbon emissions and mount- discovered that sprinkling iron dust in the right ocean waters ing evidence of climate change have taken the debate beyond could trigger plankton blooms the size of a small city. In turn, academic circles and into the free market. the billions of cells produced might absorb enough heat-trap- Today, policymakers, investors, economists, environ- ping carbon dioxide to cool the Earth’s warming atmosphere. mentalists, and lawyers are taking notice of the idea. A few Never mind that Martin companies are planning new, was only half serious when larger experiments. The ab- 340 he made the remark (in his Ocean Iron Fertilization sence of clear regulations for “best Dr. Strangelove accent,” either conducting experiments he later recalled) at an infor- An argument for: Faced with the huge at sea or trading the results mal seminar at Woods Hole consequences of climate change, iron’s in “carbon offset” markets Oceanographic Institution outsized ability to put carbon into the oceans complicates the picture. But (WHOI) in 1988. With global isn’t just an opportunity, it’s a responsibility. economists conclude that the warming already a looming growing urgency to solve our problem, others were inclined An argument against: It’s a meager, emissions problem will reward to take him seriously. temporary, unverifiable proposition involving anyone who can make iron private individuals dumping materials into At the time, ice-core re- fertilization work. 320 cords suggested that during the common waters of the world’s oceans. In past experiments “we past glacial periods, naturally A middle ground: Careful experiments were trying to answer the occurring iron fertilization conducted by scientists are our best hope question, ‘how does the world had repeatedly drawn as much work?’—not ‘how do we make (ppm) for learning how much carbon can be 2 as 60 billion tons of carbon out sequestered without harming the ocean the world work for us?’ ” Ken- of the atmosphere. Laboratory ecosystem. neth Coale, the present-day experiments suggested that director of Moss Landing every ton of iron added to the Marine Lab, said recently. ocean could remove 30,000 to “They’re totally separate. We 110,000 tons of carbon from have not done the experiment 300 CO Atmospheric the air. Early climate models hinted that intentional iron fer- to address the issues that we’re talking about today.” tilization across the entire Southern Ocean could erase 1 bil- “We’re in a learning process that involves a balance of lion to 2 billion tons of carbon emissions each year—10 to 25 science, commercial, and a whole variety of social activities percent of the world’s annual total. and interests,” said Anthony Michaels, director of the Wrig- Since 1993, 12 small-scale ocean experiments have shown ley Institute for Environmental Studies at the University of that iron additions do indeed draw carbon into the ocean— Southern California. “We’ve got to set up a measured process though perhaps less efficiently or permanently than first for moving forward.” thought. Scientists at the time agreed that disturbing the bot- The two scientists were speaking at a fall 2007 conference tom rung of the marine food chain carried risks. that brought together some 80 participants representing the 280 1000 1200 1400 Year 1600 1800 2007 4 OCEANUS MAGAZINE Vol. 46, No. 1, 2008 www.whoi.edu/oceanus 380 THE CARBON CYCLE—Carbon moves naturally through ground, ocean, and sky in a slow cycle over millions of years. People have short-circuited this cycle by quickly transferring hydrocarbons from ground to air. Iron fertilization proposes to accelerate the transfer of carbon from air back to ocean. CO2 1 Plants absorb CO2 from air to 2 Iron-rich dust is blown by winds grow, and 360 CO2 into the ocean and stimulates decompose phytoplankton blooms. to release CO2. Dust 3 Air and sea exchange CO2. 4 Phytoplankton Zooplankton 9 Rocks are take up CO2 to grow. 5 eventually eat phytoplankton But only a small percentage uplifted onto 7 and respire CO2. 340 of the sinking carbon reaches land and the deep sea. A tiny fraction is weathered to buried in seaoor sediments. release carbon Most is recycled back to the 6 Some carbon to soils and surface 100 to 1,000 years later sinks to the the atmosphere. by the ocean’s circulation. depths in the form of decaying biota and fecal pellets. 8 Over millions of years, carbon is incorporated into rocks or turned into hydrocarbons. 320 Jack Cook, WHOI scientific, commercial, regulatory, and economic sides of the host of new, worrying consequences; and its effec- debate. The conference was convened by WHOI marine geo- tiveness is difficult for anyone to measure. (ppm) chemists Ken Buesseler and Scott Doney, and Hauke Kite- In certain regions, including the equato- 2 Powell of the WHOI Marine Policy Center. In talks and rial and north Pacific and the entire South- wide-ranging discussions, participants raised serious doubts ern Ocean, a simple iron addition does cause about the practicality, efficacy, and safety of large-scale iron phytoplankton to grow rapidly. But tiny fertilization. Yet many also seemed to accept that more sci- zooplankton, known as “grazers,” eat ence—in the form of carefully designed and conducted ex- much of the bloom almost as soon as it 300 CO Atmospheric periments—is the best way to resolve those doubts, one way starts. This begins a chain of recycling or the other. that ensues from the sea surface to the seafloor as grazers, krill, Not as simple as it sounds fish, whales, and microbes Martin made his pronouncement jokingly because he eat, excrete, and decom- knew that he was glossing over several hindrances to us- pose. Much of the im- Atmospheric carbon ing iron fertilization to sequester carbon in the ocean. Op- mense carbon prize dioxide levels have ponents to the idea are quick to point out the three major won by iron increased precipitously ones: It may be less efficient than it at first seems; it raises a addition since the 1850s, and continue to rise. 280 1000 1200 1400 Year 1600 1800 2007 WoodS holE OCEANOGRAPHIC INSTITUTION 5 Ken Buesseler, WHOI IRON EXPERIMENTS OFF ANTARCTICA—Scientists aboard the Australian research vessel Aurora Australis studied the natural cycling of iron in the Southern Ocean in 2001. Ken Buesseler, a marine chemist at Woods Hole Oceanographic Institution, was aboard that expedition, and in 2002 he served as chief scientist of the Southern Ocean Iron Experiment (SOFeX). The three-ship operation investigated the results of adding iron to stimulate a phytoplankton bloom in the Southern Ocean. quickly leaks back into the atmosphere as building blocks needed for plankton growth. corals, or warm the surface layer and change carbon dioxide gas. “You might make some of the ocean circulation patterns. What is critical for the effectiveness of greener by iron enrichment, but you’re go- On the other hand, more plankton iron fertilization schemes is the amount ing to make a lot of the ocean bluer,” said might produce more of a chemical called of organic carbon that actually sinks from Robert Anderson, senior scholar at Lamont- dimethylsulfide, which can drift into the at- the surface and is sequestered in the depths Doherty Earth Observatory. mosphere and encourage cloud formation, (see Page 10). Only a small percentage of Other participants at the WHOI confer- thus cooling the atmosphere and helping to carbon—in the form of dead cells and fecal ence—John Cullen, a biological oceanog- counteract greenhouse warming. And oth- pellets—falls to the seafloor and stays there, rapher at Dalhousie University in Canada, ers argue that increased plankton supplies unused, for millennia. A higher percentage Andrew Watson, a biogeochemist at the might enhance fish stocks. (between 5 and 50 percent) will at least reach University of East Anglia, U.K., and Then there is the practical problem of middle-depth waters, where the carbon will Jorge Sarmiento, a modeler at Princeton’s verification. Iron fertilization companies remain for decades. Proponents consider this Geophysical Fluid Dynamics Laborato- would earn profits by measuring how much result good enough to buy society time to ry—pointed out several other ecological carbon they sequester and then selling the come up with other, more permanent solu- concerns. Large-scale iron fertilization, in equivalent to companies (or people) that ei- tions to greenhouse gas increases. altering the base of the food chain, might ther wish to or are required to offset their Beyond the inefficiency of carbon seques- lead to undesirable changes in fish stocks emissions. Any plan to sell sequestered car- tration, iron fertilization would likely cause and whale populations. Increased decom- bon requires a reliable accounting, and this other changes “downstream” of the ocean position of sinking organic matter could promises to be difficult in the ocean. patches where iron was added (see Page deprive deep waters of oxygen or produce So far, only three of 12 iron addition 14). The huge green phytoplankton blooms other greenhouse gases more potent than experiments have been able to show con- would take up not just iron but other nutri- carbon dioxide, such as nitrous oxide and clusively that any sequestration happened ents, too—nitrate, phosphate, and silica— methane.