Iron Fertilization of Oceans is Proposed to Absorb CO2

Scientists at Woods Hole Oceanographic Institution (WHOI) have hosted an international, interdisciplinary conference to discuss the proposal of spreading slurries of dissolved iron into the oceans in order to "fertilize" the waters.

The proposed "iron fertilization" would promote vast blooms of phytoplankton, which are a species of marine plant. Scientists and engineers have proposed fertilizing the ocean as a means to combat rising concentrations of greenhouse gases in the atmosphere.

The mechanism at work behind the proposal is that phytoplankton consume carbon dioxide (CO2) as they grow. This growth can be stimulated in certain ocean basins by the addition of iron, which is a necessary micronutrient for phytoplankton growth.

The relevant theory is that if you make such carbon-dioxide consuming phytoplankton blooms large enough, you could remove excess CO2 from Earth's atmosphere. Once removed, it would be carried down into the deep ocean since all organic matter in the ocean sinks, as do fecal pellets and dead plankton.

The accumulation and subsequent sinking of the organic matter which is CO2 would thus reduce the impact of green house gasses and global climate warming.

Dissolved iron is common on land, although it is often rare in the ocean: dissolved iron is often not an element naturally found in ocean waters. Some researchers and commercial interests have recently proposed to introduce this missing nutrient, and that on a large scale, in order to create artificial phytoplankton blooms.

Scientists took a serious interest in the idea in the late 1980s after oceanographer John Martin famously (or infamously) told colleagues in what was said to be a Dr. Strangelove-type voice: "Give me half a tanker of iron and I'll give you the next ice age." The implication being that so much phytoplankton would be produced and so much CO2 absorbed that global temperatures would plummet, which is a reference to Antarctic ice core samples that show a correlation between CO2 and temperature.

Iron fertilization experiments have since been executed and the theory tested in at least a dozen experiments around the world. The results have varied, but in general, iron fertilizers have been shown to promote plant growth in surface waters.

Many researchers remain skeptical about whether the process removes carbon dioxide from the atmosphere for the long term. There is some speculation that the removal of CO2 through this means may be only temporary--for the short term.

Most significantly, ecological impacts from long-term, large-scale fertilization are unknown and thus an important concern.

"There are many critical questions that require both better scientific understanding and an improved legal, economic, and political framework before iron fertilization can be considered either effective or appropriate," said Ken Buesseler, a senior scientist in WHOI's Marine Chemistry and Geochemistry Department and a participant in two iron fertilization experiments at sea. "The time is right to bring scientists, policymakers, and commercial interests together to inform each other and the public." Therefore the Woods Hole conference and symposium focused on inquiry into the following questions:

Efficacy: Can iron fertilization work?
Research: What do we already know, and what could future studies, models, and experiments tell us?
Consequences: What will be the intended and unintended impacts?
Policy: What are the economic, social, and regulatory considerations?

Woods Hole Oceanographic Institution is a private, independent organization in Falmouth, Mass., dedicated to marine research, engineering, and higher education...Its primary mission is to understand the oceans and their interaction with the Earth as a whole, and to communicate a basic understanding of the ocean's role in the changing global environment.

"Woods Hole Symposium Considers the Issues Involved in Using the Seas as a Solution to Global Warming," Woods Hole Oceanographic Institution.