PhD opportunity on Southern Ocean iron sources and fluxes, University of Tasmania, Hobart, Australia

Project: Southern Ocean iron sources and fluxes, constraining the provenance and quantifying the flux of lithogenic inputs to the Southern Ocean

The input and dissolution of continental material to high nutrient surface waters of the Southern Ocean plays an important role in biogeochemical cycling of carbon because it alleviates iron limitation and stimulates phytoplankton growth. Close to Antarctica, dissolved iron sources include melting sea ice, icebergs calved from glaciers, and upwelled deep waters. The Antarctic Ice Sheet is experiencing rapid changes in response to anthropogenic climate warming. Melting ice shelves and glacier retreat will increase the input of freshwater and dissolved continental material to the surface ocean, but the biological response to these changes (and therefore impact on the global carbon cycle) is unknown. The focus of this PhD project is to determine the sources and quantify the flux of dissolved iron along the continental margin of East Antarctica and compare these data to similar measurements across the Southern Ocean.

This project will focus on samples collected on the 2024 RV Investigator GEOTRACES voyage from Perth to East Antarctica. A suite of geochemical methods will be applied to seawater, aerosols, suspended particles, sea ice cores and sediment traps to quantify the input of iron to the Southern Ocean from different sources. Thorium isotopes and trace metals will be applied to estimate the supply of iron from lithogenic sources associated with glacial and sea ice melt, benthic sediments, and dust deposition. Thorium is very insoluble in seawater and as it dissolves from continental material it rapidly adsorbs to the surface of particles, making it an excellent tracer of dissolved components. Neodymium isotopes trace the source of particles and the chemical interactions at the continental-ocean boundary. The mineralogy of aerosols and particles will be investigated using scanning electron microscopy and Fe speciation assessed using X-ray Absorption Spectroscopy analysis following Shoenfelt et al. (2018) in collaboration with ANSTO. Leaching experiments on aerosol and suspended particles following Roy et al. (2013) and Robinson et al. (2008) will also be applied to investigate the bioavailability of different iron sources. Further investigation into the provenance of sedimentary Fe could also be applied using radiogenic isotopes (Pb, Nd and Sr).

Deadline for applications: 1 February 2024

For further information and applications: