Dumping iron sulphate in sea a cure for climate change: study

A team of researchers led by a German scientist found that carbon can be kept out of the atmosphere for many centuries if released in sea, where phytoplankton when sinking to the sea floor takes the carbon with it, 'The Guardian' reported.

The team added seven tonnes of iron sulphate to the ocean near Antarctica, where iron levels are extremely low. Addition of this nutrient resulted in a massive bloom of phytoplankton within a week.

As the phytoplankton began to die after three weeks, they sank towards the ocean floor, taking the carbon they had incorporated with them, the report said.

After a month of monitoring nutrient and plankton levels from the surface to the depths the team concluded at least half of the bloom had fallen to depths below 1,000m and that a substantial portion was likely to have reached the sea floor at 3,800m.

The scientists said in the journal Nature that the carbon is therefore likely to be kept out of the atmosphere for many centuries or longer.

"Ocean iron fertilisation could bury at most 1 gigatonne of CO2 per year compared to annual emissions of 8-9Gt, of which 4Gt accumulates in the atmosphere. But sequestering some CO2 could make the difference between crossing a climate 'tipping' point, where feedback effects lead to runaway global warming," Professor Victor Smetacek, at the Alfred Wegener Institute for Polar and Marine Research in Germany, who led the new research was quoted by the paper as saying.

Smetacek added that ocean iron fertilisation is much cheaper than other possible geoengineering techniques.

Some researchers have warned of other issues that might prevent the iron fertilisation of the ocean as being a useful geoengineering technique.

"The ocean's capacity for carbon sequestration in low-iron regions is just a fraction of anthropogenic CO2 emissions, and such sequestration is not permanent, it lasts only for decades to centuries," said Ken Buesseler, at the Woods Hole Oceanographic Institution in the US.