University of Tasmania, Australia

Tracing the sources of key trace elements important for Southern Ocean productivity

Southern Ocean phytoplankton production is unquestionably limited by the availability of the key micronutrient iron.  Change in the delivery and availability of iron is likely to be the single largest forcing of Southern Ocean ecosystem productivity and health in the next century, and thus is intrinsically linked with changes in climate.  We cannot at present predict how such change will develop without characterising, both spatially and temporally, the different sources and sinks of iron in Antarctic ecosystems, and their intimate links between the lithosphere, the oceans and the atmosphere. This project aims at mapping the distribution of manganese in the Southern Ocean as a means to fingerprint the location and magnitude of trace element inputs to the iron-deficient Antarctic surface waters. The task will be achieved in three steps: (i) Development of an analytical methodology for manganese that is sensitive, precise, rapid, minimises the risk of sample contamination and operable on-board research vessels; (ii) Mapping the dissolved and particulate manganese distributions from a series of archived seawater, snow, brine and sea ice samples; and (iii) modelling the assimilated data to constrain the biogeochemistry of manganese in marine waters. The results will be coupled to existing datasets for other trace elements (such as aluminium), which will enable us to estimate iron availability and fluxes to the surface ocean from melting sea ice, dust and resuspended shelf sediments.

The successful applicant will join an active team that is working on important aspects of trace elemental biogeochemistry in the Southern Ocean. The student will develop skills in: (i) retrieval and application of oceanography data; (ii) shipboard/non-contaminating sampling and analysis of micronutrients; (iii) interdisciplinary analysis and synthesis; and (iv) numerical modelling of micronutrients.  These skills will be useful to students interested in a range of possible career directions, including analytical/environmental chemistry, fate of marine contaminants, and the impacts of climate change and variability on global biogeochemical cycles.