Southern Ocean biological pump

Application of Thorium-230 to quantify the biological pump in the Southern Ocean

Degree type


Closing date

25 September 2023



Citizenship requirement

Domestic / International

About the research project

The ocean's biological carbon pump is a key component of the earth's carbon cycle and climate. Changes in the operation of the biological carbon pump impact atmospheric carbon dioxide concentrations and therefore climate. One major uncertainty is the depth to which organic carbon is exported before being degraded, or remineralised, back to dissolved inorganic carbon, and how this varies spatially and is regulated by factors such as temperature, oxygen and community composition. Observational constraints on how much sinking carbon reaches different ocean depths are needed to resolve this uncertainty, particularly in the poorly sampled Southern Ocean.

The biological pump in the Southern Ocean is inefficient due primarily to iron limitation.  Despite this poor efficiency, the amount of carbon exported in the Southern Ocean is high, representing ~25% of carbon exported via the biological carbon pump.  Large zonal gradients in phytoplankton community composition across the Southern Ocean, coupled with its importance on the global scale, make the Southern Ocean a key focus for studies of the biological carbon pump.

This PhD project will quantify carbon export as a function of depth in the Southern Ocean using a relatively new method based on the radioisotope Thorium-230. Samples collected along a zonal transect in the Indian Ocean, from Perth to Antarctica, will be the primary focus, supplemented by samples collected in the Subantarctic zone and the Antarctic slope. There may be opportunities for the student to participate in research voyages to collect new samples. Note that there is some flexibility in the direction of this project. For example, depending on student interest and aptitude this project could include a component of modelling or model-data comparison. Alternatively, a slight variation of the same Th-based approach can be used to estimate dust fluxes, and estimates of dust flux could be compared to estimates of carbon export.

Primary Supervisor

Meet Prof Zanna Chase


Applicants will be considered for a Research Training Program (RTP) scholarship or Tasmania Graduate Research Scholarship (TGRS) which, if successful, provides:

  • a living allowance stipend of $31,500 per annum (2023 rate, indexed annually) for 3.5 years
  • a relocation allowance of up to $2,000
  • a tuition fees offset covering the cost of tuition fees for up to four years (domestic applicants only.

If successful, international applicants will receive a University of Tasmania Fees Offset for up to four years.

As part of the application process you may indicate if you do not wish to be considered for scholarship funding.

Other funding opportunities and fees

For further information regarding other scholarships on offer, and the various fees of undertaking a research degree, please visit our Scholarships and fees on research degrees page.


Applicants should review the Higher Degree by Research minimum entry requirements.

Ensure your eligibility for the scholarship round by referring to our Key Dates.

Additional eligibility criteria specific to this project/scholarship:

  • Applicants must be able to undertake the project on-campus

Selection Criteria

The project is competitively assessed and awarded.  Selection is based on academic merit and suitability to the project as determined by the College.

Additional essential selection criteria specific to this project:

  • Critical thinking skills
  • Relevant science degree with chemistry and/or geoscience
  • Good communication (writing, oral)
  • Good quantitative skills

Additional desirable selection criteria specific to this project:

  • Chemical laboratory experience
  • Basic coding

Application process

  1. Select your project, and check that you meet the eligibility and selection criteria, including citizenship;
  2. Contact Prof Zanna Chase to discuss your suitability and the project's requirements; and
  3. In your application:
    • Copy and paste the title of the project from this advertisement into your application. If you don’t correctly do this your application may be rejected.
    • Submit a signed supervisory support form, a CV including contact details of 2 referees and your project research proposal.
  4. Apply prior to 25 September 2023.

Full details of the application process can be found under the 'How to apply' section of the Research Degrees website.

Following the closing date applications will be assessed within the College. Applicants should expect to receive notification of the outcome by email by the advertised outcome date.

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