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The University of Southampton
Ocean and Earth Science, National Oceanography Centre Southampton

Research project: Iron Isotopes in seawater samples

Currently Active:

Photosynthesis in the world's upper ocean relies on the availability of iron (Fe), which is a limiting factor in extended oceanic regions due to its low concentrations. Given that marine photosynthesis is responsible for ~40% of the global atmospheric carbon dioxide (CO2) uptake, oceanic Fe availability plays a major role in the global climate. The measurement of Fe isotopes is a promising tool to estimate the flux strengths of Fe delivered from different sources to the ocean (atmospheric, continental, hydrothermal). Fe isotopes also provide information about the internal cycling of Fe in the ocean, as the isotopic composition of Fe is subject to alteration during several processes, such as biological uptake, bacterial remineralisation, organic complexation, redox reactions, etc.

Trace Metal Rosette deployment aboard the RRS James Cook during cruise JC068
Trace metal sampling

Analytical procedure

At NOCS, Fe is extracted and purified from seawater samples in a class 100 clean lab and isotopic measurements are performed on a Neptune multi collector ICP-MS.

Fe purification using an anion exchange technique in a class 100 clean lab at NOCS
Fe purification

Sampling areas

  • Vertical and surface samples from the Oxygen Minimum Zone (OMZ) of enhanced Fe concentrations, tropical Atlantic; GEOTRACES (+intercomparison samples with University of South Carolina)
  • Surface samples from 40 o S Atlantic GEOTRACES transect which has relatively enhanced productivity (+ intercomparison samples with University of South Carolina)
  • Vertical and surface samples from the Arctic Ocean
  • Hydrothermal samples; East Scotia Ridge
  • GEOTRACES stable isotopes intercomparison programme 2013
Thermo Fisher MC-ICP-MS Neptune

Scientific aims

  • Development of a technique to measure Fe isotopes in seawater samples of low Fe concentration at NOCS.
  • Validation of the technique through intercomparison exercises with University of South Carolina (USA); LEGOS (France); and the GEOTRACES stable isotope intercomparison programme 2013.
  • Fe isotope analysis of seawater samples ranging from 0.1 to 2 nM Fe and hydrothermal samples of typically >10 mM Fe.
  • General interpretation of Fe fluxes and Fe cycling in the oceans.

Key Contacts

Miss Jessica Klar (Postgraduate Research Student)

Prof Rachael James (Project supervisor)

Prof Eric Achterberg (Project supervisor)

Dr Douglas Connelly (Collaborator)

Dr Martha Gledhill (Collaborator)

Dr Ian Parkinson (Collaborator, Open University)

PhDs and Other Opportunities


Associated research themes

Past Present and Future Environmental Change

Environmental Geochemistry and Radioactivity

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