Iron fertilization
Iron fertilization is a proposed method for combating global warming by introducing iron into ocean waters to stimulate phytoplankton blooms. Phytoplankton, microscopic plants in the upper ocean layers, require light and essential nutrients, including trace metals like iron, to thrive. When conditions are favorable, these blooms can significantly absorb carbon dioxide from the atmosphere. Beginning in the late 1980s, small-scale experiments demonstrated that adding iron could indeed trigger such blooms, but results have been mixed and the effectiveness of this method in capturing carbon has been questioned. Factors such as ocean mixing and the fate of carbon after phytoplankton death complicate the potential benefits, with much of the absorbed carbon potentially returning to the atmosphere through marine food webs. While larger experiments have been conducted, they have not conclusively shown that iron fertilization can lead to substantial reductions in atmospheric carbon dioxide levels. Ongoing research, including computer modeling initiatives funded by the US government, aims to enhance understanding of this approach and address its complexities.
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Iron fertilization
DEFINITION: Purposeful introduction of iron into the oceans on a large scale to encourage plankton blooms as a measure to decrease global warming by removing carbon dioxide from the atmosphere
Small-scale experiments have tested the technique of iron fertilization, but the results were not conclusive, and conducting experiments on a larger scale is problematic for several reasons. How much of a role iron fertilization may eventually play in efforts to remove large amounts of carbon from the atmosphere remains unknown.
Phytoplankton are microscopic plants (algae) that can be found throughout the upper layers of the world’s oceans. These tiny plants require light as well as inorganic material such as phosphate, nitrate, ammonium, carbon dioxide, or carbonate, along with some trace metals such as iron or zinc. Phytoplankton reproduce asexually, with a typical ocean doubling time of a from a few hours to a few days. Under the right conditions and with access to abundant nutrients, form blooms that can cover hundreds of square kilometers of ocean and are readily visible to satellites orbiting the earth. Such blooms can remove from the atmosphere large amounts of carbon dioxide, a that has been linked to global warming. Among the natural causes of such large are hurricanes, which bring up nutrients from lower ocean depths into the upper reaches of the oceans.
Since the late 1980s scientists have known that depositing particles of iron in warm ocean waters can trigger plankton blooms, and by the early 1990s, twelve small-scale experiments involving the introduction of a ton or more of iron dust into a few hundred square kilometers of ocean had shown that massive blooms could be stimulated artificially. These experiments also raised a number of problems and complicated earlier views, however. First, the rate at which carbon was taken up by the was many times lower than had been predicted on the basis of laboratory experiments. Some of this difference was the result of the chaotic mixing that occurs in the oceans, as well as the difficulty of placing iron dust in the oceans under just the right conditions to prevent the dust from too quickly into lower depths. Second, the degree to which the carbon remained locked up in the plankton (which upon death would to the seafloor, thus relatively permanently sequestering the carbon) was shown to vary considerably. Many plankton would be consumed, and the carbon would begin a journey through the food chains of the ocean; ultimately, much of it would reenter the atmosphere as carbon dioxide.
A few large-scale iron fertilization experiments have been undertaken, but no evidence has yet been produced that this method could substantially reduce the amount of carbon dioxide present in the atmosphere. Critics have argued that no large-scale experiment will be able to determine fully the effectiveness of this technique because of the very long timeframe within that such an experiment would require, as well as the potent technical difficulties involved in effectively the impacts of such experiments even in the short term over the vast reaches and depths of the world’s oceans. However, in 2023, scientists with the Woods Hole Oceanographic Institute received $2 million in funding from the US government to pursue research on the idea using computer modeling.
Bibliography
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Goodell, Jeff. How to Cool the Planet: Geoengineering and the Audacious Quest to Fix Earth’s Climate. Boston: Houghton Mifflin, 2010.
Hance, Jeremy. "Is Ocean Iron Fertilization Back from the Dead as a CO2 Removal Tool? Mongabay, 14 Nov. 2023, news.mongabay.com/2023/11/is-ocean-iron-fertilization-back-from-the-dead-as-a-co%E2%82%82-removal-tool/. Accessed 18 July 2024.
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