Ocean Iron Fertilization

Today, there is a growing consensus that climate restoration, or greenhouse gas removal, is necessary for protecting our future. Climate scientists have been warning against increasing carbon dioxide levels in the atmosphere for the past 35 years. Most recently, the amount of carbon dioxide in our atmosphere has reached over 420 parts per million (ppm), the highest it’s been in at least 3 million years. Even if we reach net zero and stop all emissions tomorrow, it won't be enough. The legacy carbon already in the atmosphere will continue to trap heat, leading to ecosystems collapsing, ice sheets melting, and more extreme weather events such as heatwaves, hurricanes, droughts, and floods.

So what is the solution? Ocean Iron Fertilization (OIF) is a geoengineering process which dumps large amounts of iron into the ocean to stimulate the growth of phytoplankton, tiny photosynthetic organisms that form the base of the marine food web. Iron incentivizes the growth of phytoplankton which absorb CO2, before dying and capturing that carbon at the bottom of the ocean in a phenomenon known as marine snow.

In many parts of the ocean, especially in High-Nutrient, Low-Chlorophyll (HNLC) regions like the Southern Ocean and the equatorial Pacific, iron is scarce. Even though other nutrients like nitrates and phosphates are abundant, phytoplankton can't grow much without iron.According to researcher David Emerson, iron is insufficient in 30% of the ocean which limits phytoplankton populations (Bigelow Laboratory, 2019). This iron depletion has meant the oceans are absorbing 4% less Carbon. (Scientific American, 2006). According to a 2004 study, Ocean iron fertilization incentivizes phytoplankton to intake 34 times the speed of natural rates. (Scientific American, 2012). A Department of Energy funded study found that one ton of iron being added to an area of 400 square miles could produce phytoplankton to remove 1800 tons of carbon. (SOFeX, 2002). Ocean Iron Fertilization has the ability to offset a significant amount of carbon production by burying it for centuries (The Guardian, 2012).

Scientists or engineers add iron compounds (often iron sulfate) to the surface waters of these regions. The added iron promotes phytoplankton blooms and the more phytoplankton, the more photosynthesis is performed, and the more carbon is sequestered. When phytoplankton die, some sink to the ocean floor, potentially trapping the carbon they absorbed for decades or centuries.

Ultimately, climate restoration is the future of all climate action. Reducing emissions is essential, but it’s only half the equation. The other half is removing the excess CO₂ we've already released, carbon that will otherwise continue to heat the planet and acidify the oceans for centuries. Ocean Iron Fertilization isn’t a silver bullet. It needs more research, international regulation, and environmental safeguards to avoid disrupting marine ecosystems. But in a world running out of time, it represents a low-cost, scalable, and promising strategy to pull carbon out of the atmosphere and help stabilize our climate.