▻ Fertilization using iron can increase the uptake of CO2 across the sea surface. ▻ But most of this uptake is transient; long-term sequestration is difficult
• 1988: Fe fertilization proposed as a method of “curing” greenhouse effect (Gribbin, J., Nature 331, 570, 1988) • 1990 Martin suggests iron instrumental in causing lower atmospheric CO2 concentrations in glacial time. • Open ocean diatoms have an Fe-limited C:Fe ~3 x 105 • However, the ratio of phytoplankton C sequestered to Fe added is much lower than this in Iron enrichment experiments: • Ironex II: C:Fe = 3 x 104 (fixed, not necessarily sequestered) • SOIREE: 0.2 - 0.8 x 104 • SOFEX 0.7 x 104 (sequestered below 100m, Buessler etal) • Fe may be used more efficiently – By larger-scale, longer time fertilizations?
Jack Cook, WHOI TESTING THE WATERS—Twelve small-scale experiments over the past decade in several ocean locations (red dots) consistently showed that intentional iron additions do result in phytoplankton blooms that help draw down carbon dioxide from the air. From Philip Boyd, New Zealand National Institute for Water and Atmospheric Research Woods hole oceanographic institution 11 0 to 100 meters 100 to 500 meters Below 500 meters THE BOTTOM LINE—Only a small fraction of the carbon drawn into the ocean by plankton blooms makes it into the depths where it no longer can be exchanged with the atmosphere. But there is already enough plankton growth in equatorial waters to eventually use up their nutrient supply anyway; add-ing iron there just creates a faster, concen-trated bloom in a specific location, but the net effect on atmospheric carbon dioxide levels is arguably negligible.
* *After a hiatus of more than 10 years, a new round of research into ocean iron fertilization is set to begin, with scientists saying the controversial geoengineering approach has the potential to remove “gigatons per year” of carbon dioxide from Earth’s atmosphere.*. * *Scientists with the Woods Hole Oceanographic Institution in Massachusetts, U.S., recently received $2 million in funding from the U.S. government that will enable computer modeling research that could pave the way for eventual in-ocean testing, effectively reviving research into ocean iron fertilization.*. Since then, except for an even more controversial attempt by a for-profit company in 2012 in Canadian waters, there have been no large-scale experiments of ocean iron fertilization as a potential tool to counteract climate change. They say they hope such a scaled-up experiment will answer many of the questions that still remain about the efficacy of ocean iron fertilization.
“The ocean covers 70% of our planet and has a considerably larger capacity than both the land and atmosphere for carbon storage—thus augmenting the ocean’s natural ability to store carbon should be explored as a potential strategy to curb warming,” according to Deborah Steinberg, a professor at William & Mary’s Batten School at Virginia Institute of Marine Science (VIMS) and co-author on the study. Now, an article published in the journal *Frontiers in Environmental Engineering*, “Next steps for assessing ocean iron fertilization for marine carbon dioxide removal” spells out the work needed to assess the potential of OIF as a low cost, scalable, and rapidly deployable method of mCDR. “Despite calls by the US National Academy of Science for research on carbon dioxide removal (CDR) – including marine CDR – there has been a significant gap in substantial open-ocean CDR research experiments in recent years, leaving the true efficacy and impacts of these methods largely uncertain,” said Margaret Leinen, Director of the Scripps Institution of Oceanography.
There are many potential approaches to marine carbon dioxide removal (mCDR), of which ocean iron fertilization (OIF) has the longest history of study. There are many different approaches to marine carbon dioxide removal (mCDR), of which ocean iron fertilization (OIF) has the longest history of study and field testing (NASEM, 2022). By then, we would have determined the most efficient and bioavailable forms of iron and delivery systems, and expanded the use of AVs for iron delivery, with improved MRV and eMRV to establish OIFOs. These operational improvements in Phase I will make working in other sites more efficient and cost effective as we move to significantly more challenging settings such as the Southern Ocean, where the high nutrient concentrations increase the potential for OIF to impact global atmospheric CO2 removal.
The availability of iron limits primary productivity and the associated uptake of carbon over large areas of the ocean. Iron thus plays an
This paper presents a basic cost model for undertaking ocean iron fertilization (OIF) as a means of removing carbon dioxide from the atmosphere.