Iron Biogeochemistry

The oceans provide half of Earth’s primary production.

This photosynthetic fixation of carbon by microscopic plants (phytoplankton) is controlled by iron-supply over much of the ocean, making the global iron-cycle central to Earth’s functioning. While phytoplankton in remote regions (e.g. the Southern-Ocean) are anaemic, desert dusts are iron-laden. Long-distance atmospheric transport of this dust helps to alleviate oceanic anaemia, boosting productivity. The immediate dissolution of iron from this dust into the ocean (2%) has been well studied, yet the fate of the remaining dust has been ignored.

Does more of it dissolve and enhance primary production? Or does it just sink into the abyss? With dust storms forecast to increase in the future, understanding the destiny of this remaining 98% will improve predictions of the impact of dust-storms on the ocean’s ability to sequester carbon. Using iron stable-isotopes (iron atoms with different masses), we will trace the different sources and pathways within the oceanic cycling of iron over the long term. Due to their relatively light mass, these iron-isotopes fractionate through a wide range of natural biotic and abiotic processes, providing the discriminatory power needed to resolve the fate of aerosols as they are altered during weeks and months in the upper ocean.

Currently we are receiving funding through a Marsden grant titled: From soils to seas: how does the long-term fate of aerosol iron impact ocean productivity and global climate (Principal Investigator: Sylvia Sander, Associate Investigators: Phil Boyd, Keith Hunter, Claudine Stirling, and Michael Ellwood (ANU, AU); Postdoctoral Fellow: Melanie Gault-Ringold). Other projects vary from remotely sensing iron supply and demand from space, to operating a ship of opportunity aerosol dust sampling time series between Japan and New Zealand (Phil Boyd).

There has been a large number of students being involved in the research topic currents ones include Sruthi Thalayappi, Phillip Nasemann, and Anoop Chandrasekhar)