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One method suggested for reducing carbon concentrations in the atmosphere has been to sink it into the ocean. Ocean fertilisation involves adding nutrients such as iron or nitrogen to the sea to stimulate phytoplankton in the hope of sequestering carbon dioxide in fish stocks. Associate Professor Thomas Trull of the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart says that scientific models show the maximum amount of carbon that could be sunk into the ocean is less than 15% of the world’s annual human generated greenhouse emissions. Although that is assuming the technology works and it is possible to verify sequestration. “The total capacity is about 1 Gigatonne of carbon a year,” he says.
According to Trull, no studies have been specifically designed to look at the risks of ocean fertilisation but evidence suggests possible risks include upsetting the food web and creating dead zones in the ocean. Risks could also include producing worse greenhouse gases like nitrous oxide and methane, blocking penetration of sunlight, trapping more heat or changing ocean circulation, he says. Using nitrogen is “more risky” than using iron, because it stays in the system for millennia, compared to iron, which sinks into sediments by natural processes over decades or a century at most.
The full report, by Anna Salleh from the ABC is “Cut not sink” emissions, says expert.
Dr Lee Kump, Penn. State University Interview: “Anoxic ocean events” (From ABC’s “CRUDE” – video)
“Ocean Acidification – the BIG Global warming story” on Catalyst (video)
