Sea-green project may not be iron-clad

From The Australian: Sea-green project may not be iron-clad

THOUSANDS of tonnes of iron will be dumped at sea in the biggest trial of a technique that could cut global warming.

The iron will seed vast blooms of phytoplankton, which absorb CO2 as they grow. When they die, these microscopic plants sink to the bottom of the ocean, locking away the carbon in their bodies for more than a century.

Ships and aircraft would spray iron sulphate liquid over 10,000sq km of the Southern Ocean in a five-year international trial costing about $120 million that is being planned by the National Oceanography Centre at the University of Southampton.

On a global scale, ocean fertilisation could remove up to a billion tonnes of carbon a year from the atmosphere, or 12 per cent of the total produced by human activities. The process could prove much cheaper than cutting emissions and could eventually be funded by businesses to offset their consumption of fossil fuel.

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But scientists admit the trial, which would be 100 times larger than previous tests of ocean fertilisation and involve up to 600 tonnes of iron each year, could have side-effects on marine life. The decaying phytoplankton would reduce oxygen in the deep water, potentially resulting in more dead zones where few sea creatures can survive. The carbon could also make the deep ocean more acidic, weakening the shells of clams and other shellfish.

And there is a risk the iron could result in an increase in nitrous oxide emissions, a far more powerful greenhouse gas than CO2. Near the surface, the iron would increase the food supply and fish stocks could multiply.

Richard Lampitt, professor of oceanography at Southampton, said the trial would measure impacts as well as test how much carbon was sequestered.

Previous trials demonstrated that iron does increase plankton blooms but did not measure how much sank to the bottom. His team is approaching private bodies and philanthropists to fund the trial. Professor Lampitt said such techniques for deliberately altering the climate, known as geoengineering, were too controversial to attract government funding. "Public bodies are quite nervous about this sort of activity," he said. The trial will need to be approved by the UN London Convention, which regulates the dumping of substances at sea. Professor Lampitt sits on the convention's scientific advisory group.

He said the trial would simply accelerate the ocean's natural rate of absorption of CO2 under which emissions end up at the bottom of the sea over the next thousand years.

"No method of geoengineering is going to be a silver bullet for climate change but ocean fertilisation is one of several ways that could make a contribution."

A royal society report on geoengineering last year expressed concern about the potential side-effects of ocean fertilisation and said that a lot more research was needed.