Iron Fertilization: “Give me half a tanker of iron and I’ll give you the next ice age.”

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What if, to prevent global warming, humanity fertilized the ocean with iron? That is the question scientists will be discussing at an international Woods Hole Oceanographic Institution conference from September 26-27.

The idea became more mainstream after oceanographer John Martin famously told his colleagues, “Give me half a tanker of iron and I’ll give you the next ice age.”

Dissolved iron is rare in the ocean. Iron is a vital nutrient for phytoplankton growth and photosynthesis. Ocean zones that are iron-deficient have small phytoplankton populations, if at all.

Phytoplankton, like any other life form that obtains energy through photosynthesis (e.g. plants), absorbs carbon dioxide. Unlike most other plants, when phytoplankton dies, the CO2 is not necessarily immediately released in to the atmosphere. When most plants die, they decompose and the carbon dioxide is released in to the atmosphere. Phytoplankton lives in the ocean. When it dies, it sinks to the bottom of ocean, bringing the CO2 with it. That CO2 can stay down there for hundreds of years.

The idea is that iron fertilization would dramatically increase the phytoplankton population, who would then absorb carbon dioxide.

Critics argue that not enough research has been done on large-scale effects. Some worry that harmful algae could bloom as well, ecosystems could be disrupted, or that areas could become oxygen depleted.

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