In a study published in Nature Geosciences, the researchers report the first measurements of the concentration of dissolved iron in the Southern Ocean, at depths of up to four kilometres below the surface. This iron is produced by the volcanoes and vents that run along plate boundaries under the sea.

Phytoplankton need iron to bloom, but it’s generally in short supply in the Southern Ocean. As the single-celled organisms grow, they absorb CO2, and when they die and sink to the bottom of the ocean, this carbon is locked up, sometimes for centuries.

Most of the iron in the Southern Ocean comes from wind-blown dust, but the new research has shown that a significant amount is of volcanic origin. ‘There have been a number of studies showing iron is released from deep sea volcanoes, but no study has considered that on a global level and considered its importance on Southern Ocean carbon storage,’ said one of the study’s authors, Andrew Bowie, of the Antarctic Climate and Ecosystems Cooperative Research Centre in Hobart, Tasmania. 

According to the researchers, the iron produced by undersea volcanoes is stable of long timescales and is responsible for 5–15 per cent of the total Southern Ocean carbon storage, rising to 30 per cent in some areas.     

Shira Pinczuk
May 2010