Major discussions around climate change have focused on one thing: how much carbon is in the air — and how to reduce it. However, what is rarely talked about but may become very important is how much carbon is in our oceans. The ocean contains 50 times more carbon than the atmosphere. Some climate researchers believe that if we could slightly increase the amount of carbon the oceans absorb from the atmosphere, we could avoid some of the worst impacts of climate change.
This may seem unusual when you first hear it, but think again. The ocean covers about 70 percent of the Earth’s surface, and it naturally absorbs carbon dioxide — effectively dissolving it. Phytoplankton in the ocean use this carbon dioxide and sunlight for photosynthesis, just like land plants. Oxygen is produced through this process – phytoplankton are actually responsible for about 50% of the oxygen in our atmosphere.
Some climate researchers have proposed that if we can increase the amount of phytoplankton in the oceans, we can extract more carbon from the atmosphere. A well-known method of producing phytoplankton blooms is to introduce iron, an important nutrient for plankton communities, into the water. Many parts of the ocean are so low in iron that even adding a relatively small amount of iron could theoretically produce large amounts of phytoplankton, removing a lot of carbon dioxide from the atmosphere.
“Give me half a ship of iron, and I’ll give you an ice age,” oceanographer John Martin of Moss Landing Marine Laboratory wrote in 1988. At the time, most people were just beginning to become familiar with the idea of climate change as we know it now . But this is also when people start thinking about how iron fertilization affects phytoplankton growth and, in turn, changes atmospheric carbon levels.
While climate scientists spend a lot of time discussing this strategy among themselves, there has been no concerted effort to explore it further and take it seriously. Ken Buesseler, a marine radiochemist at the Woods Hole Oceanographic Institution, is a scientist who has done some research on iron fertilization in the ocean. He and his team investigated whether introducing iron could “alter the flow of carbon to the deep ocean” and found significant carbon sequestration effects.
Buesseler told The Daily Beast that his research was done nearly 20 years ago, and there hasn’t been a lot since.
“What happened 20 years ago was we started walking around and we would spread a chemical form of iron and look for phytoplankton — the plant’s response — in fact, it did show very clearly that if you boost iron, then you can create more uptake of carbon dioxide,” Buceller said. “The difference between now and 20 years ago is that I think the climate crisis is more visible to the public.”
Using the ocean to combat climate change has become a widely discussed topic among climate scientists in recent years, and Bisseller is part of a group of scientists that released a report late last year through the National Academies of Sciences, Engineering and Medicine that looked at up among the options available, including increasing phytoplankton levels.
“We have a big reservoir. It’s already consuming a third of the greenhouse gases. The question people are asking more now is, what can we do to enhance it?” Bisseler said. “Let’s go out. Let’s experiment.”
The experiments themselves won’t do any damage to the ocean’s natural ecosystem, but they can tell us a lot about how introducing more iron to the ocean on a larger scale might affect that ecosystem in the long run, Buesseler said. He doesn’t believe doing this on a large scale will cause significant harm, but it’s important to get the research done so we can be sure. A “very conservative” estimate, he said, is that up to 10 gigatons of carbon dioxide could be sequestered each year if the process were carried out on a large scale.
“The difference between now and 20 years ago is that I think the climate crisis is more visible to the public.“
— Ken Buesseler, Woods Hole Oceanographic Institution
“It will change the type of plants and animals that grow, but that already happens with temperature and acidity,” Buselle said.
Iron fertilization is also easy to do, David Siegel, a professor of marine sciences at the University of California, Santa Barbara, told The Daily Beast. You can simply get a 120-foot fishing boat and start deploying the irons where they are most effective at stimulating phytoplankton growth.
“It can be done relatively cheaply. Every iron atom you add in the right place can hold tens of thousands of carbon atoms in place,” meaning absorbed by water. “It’s pretty effective,” Siegel said. “You can deploy containers that release iron oxide into water — or even just iron ore — and you can make flowers that you can see from space. We know that.”
The effect will happen quickly. Scientists who have introduced iron into seawater in the past have found that phytoplankton blooms can begin to manifest within the first 24 hours. The ideal location for introducing iron is the least abundant place, which would be part of the ocean – mostly in the southern hemisphere – not close to land. The iron that ends up in the ocean usually comes from dust blown into the ocean from land.
Both Buesseler and Siegel stressed that this should not be seen as an alternative to ending the use of fossil fuels. This remains critical in terms of having a chance to beat climate change. But avoiding the worst effects of climate change also requires carbon removal strategies to reduce the amount of greenhouse gases in the air.
“Even if we decarbonize the economy, there are still about 20 gigatons of carbon dioxide that needs to be removed from the atmosphere to get us close to the goals of the Paris Agreement,” Siegel said.