Changes to ocean temperature extremes

Understanding projected changes to marine heatwaves and cold spells beyond those due to simple global warming trends

Degree type


Closing date

18 July 2022



Citizenship requirement


About the research project

Marine heatwaves and cold spells, or discrete periods of prolonged ocean temperature extremes, can have devastating impacts on marine ecosystems (e.g. Garrabou et al. 2009; Wernberg et al. 2013; Smale et al. 2019). Understanding observed and projected changes to ocean temperature extremes is critical for determining whether marine species and ecosystems may have the capacity to adapt to a changing climate. A common approach to defining marine heatwaves and cold spells is based on temperatures above or below the 90th and 10th temperature percentile thresholds, respectively, relative to an appropriate baseline climatology (Hobday et al. 2016). Using such a definition, it is clear that as ocean temperatures rise under global warming, marine heatwaves have and will continue to increase in their intensity, duration, and frequency (Oliver et al., 2018). Conversely, marine cold spells have been declining. But warming rates are not uniform across the global ocean, at least in part due to the influence of modes of climate variability, such as El Niño–Southern Oscillation (Holbrook et al. 2019). An added complication is that changes to the temperature variability, on a range of time scales, can also affect longer-term changes in the extremes.

Some elements of the marine environment have the capacity to respond to unfavourable conditions, e.g. fish can migrate, and plant life may adapt. Therefore, it can be useful to employ alternative marine heatwave and cold spell definitions that account for a changing baseline climatology (e.g. Jacox et al. 2020; Chiswell 2021). With a moving baseline definition, it is also more straightforward to understand trends due to temperature variability changes.

This project will aim to:

  • Explore a range of methods for defining marine heatwaves and cold spells relative to a shifting baseline
  • Analyse a range of climate data, including observations, reanalyses, and model simulations of historical, pre-industrial and future scenarios
  • Determine whether air-sea heat flux, ocean advection, or other processes are driving changes to extremes, by calculating temperature variance budgets
  • Consider and explore adaptation time scales, and possible tipping points, for selected marine species

Primary Supervisor

Meet Dr Jules Kajtar


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 $28,854 per annum (2022 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.


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

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:

  • First Class Honours (or equivalent) or Masters degree in physical oceanography, physics, mathematics or statistics

Additional desirable selection criteria specific to this project:

  • Experience with coding in MATLAB or python
  • Experience handling climate data in a Unix environment
  • Demonstrably strong quantitative skills (background in mathematics, physics, marine biogeochemistry, fisheries science, marine ecology, or related)

Application process

There is a three-step application process:

  1. Select your project, and check you meet the eligibility and selection criteria;
  2. Contact the Primary Supervisor, Dr Jules Kajtar to discuss your suitability and the project's requirements; and
  3. Submit an application by the closing date listed above.
    • 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.
    • As part of your application, you will be required to submit a covering letter, a CV including 2 x referees and your project research proposal.

Following the application 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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