AAPP PhD Projects and Scholarships
A number of PhD research projects related to the research program of the AAPP will be advertised below and on the University of Tasmania Graduate Research website. Applicants will be able to apply for Stipend Scholarships and fee waivers from the University of Tasmania or from other sources. If successful, applicants will also receive a top-up scholarship of $6,000 per annum for 3.5 years. This scholarship is funded from the Australian Government as part of the Antarctic Science Collaboration Initiative program through the Australian Antarctic Program Partnership (AAPP).
If you are interested in undertaking a PhD with the AAPP, please check this page frequently for opportunities or contact any of our researchers directly.
The impact of Antarctic sea ice on simulated Southern Ocean watermasses
Despite being only 6% of the global ocean’s surface area, the Southern Ocean dominates the ocean’s absorption of anthropogenic heat and carbon (Frolicher et al., 2015), with critical implications for the planet’s response to increased greenhouse gas emissions. Absorbing this heat and carbon, and locking it away in the deep ocean, relies on a complex interplay of wind and buoyancy forcing that drives exchanges of sea water between the surface and deep ocean, that is poorly understood. There is strong evidence that Antarctic sea ice is an important factor in this process, by forcing surface salinity changes in the polar Southern Ocean (Abernathey et al., 2016, Haumann et al., 2016).
How well these processes are represented in coupled climate models, such as those used by the IPCC, and how that impacts global climate projections has not been explored. We do know, however, that climate models show a wide spread in how they represent Antarctic sea ice process (Schroeter et al., 2018) and Southern Ocean watermasses (Sallee et al., 2013).
In this project, the student will explore how Antarctic sea ice, and in particular its role in transporting fresh water from the Antarctic coastline to the open ocean, affects how well climate models in the latest Coupled Model Intercomparison Project (CMIP6) represent the major Southern Ocean water masses. Furthermore, the student will quantify how this relates to simulated ocean heat and carbon uptake under current and future climate conditions, and the resulting implications for global climate sensitivity.
Tidal melting of Antarctic ice shelves since Last Glacial Maxiumum
During the Last Glacial Maximum (LGM) ice sheets were substantially increased in size compared to present day, resulting in sea levels lower by 120-130m globally. Modelling suggests this reduction in ocean volume resulted in dramatic increases in ocean tide amplitudes (Arbic et al., 2004; Egbert et al., 2004; Griffiths and Peltier, 2008; Griffiths and Peltier, 2009) with consequently increased tidal current speeds. Tidal currents are now known to play an important role in present-day basal melting of Antarctica’s ice shelves (Makinson et al., 2011; Mueller et al., 2012). The interaction between the Antarctic ice sheet and tidal currents during and after LGM has not yet been examined.
The project aims to develop our understanding of what caused the ice sheet retreat since the Last Glacial Maximum. It will test the hypothesis that large tidal currents resulted in enhanced tidal melting of the ice shelves and this varied over time.
Modelling downward carbon flux in the Southern Ocean: linking ocean midwater ecology and biogeochemistry
Project 7: Krill & Ecosystems
The oceans act as major sinks of atmospheric carbon. The biological pump is the ocean’s biologically driven carbon sequestration system. It has several key pathways for sequestering carbon (e.g., gravitational pump and particle injection via diverse groups of midwater biota), however, understanding these pathways and their interactions is not easy and therefore has seldom been attempted. Often the models designed to quantify downward particulate carbon flux in the oceans lack information on key pathways and their parameterization may only focus on a limited number of these conduits. Development of a holistic model which links these ecological and biogeochemical pathways will provide a much more comprehensive and accurate picture of downward particulate carbon flux across the oceans. Such a model will enable researchers to track the oceans’ ongoing ability to sequester carbon in response to climate change.
As part of the the Joint Exploration of the Twilight Zone Ocean Network (JETZON, https://www.jetzon.org/) initiative the AAPP 2020/2021 SOLACE voyage aimed “to improve water column measurements of the downward export flux of carbon of the biological pump using an integrated suite of new technological advances from particle decomposition to mesopelagic vertical migration”.
Deriving accurate sea-ice (and snow) thickness near-real time estimates for the East Antarctic region
Project 6: Sea Ice
The seasonal evolution of the ocean-atmosphere exchange at the surface of the Southern Ocean gives rise to the formation, advection, deformation and melt of Antarctic sea ice. While observations are scarce, the existing measurements revealed substantial spatio-temporal variability in ice concentration and also ice thickness. Much of our information is based on passive-microwave derived two-dimensional measurements of the ice cover. More recently laser and radar altimetry have been supported on polar-orbiting satellites, opening possibilities to translate those into sea-ice freeboard and finally ice thickness.
This project will use remote sensing data from NASA’s ICESat-2 laser and ESA’s CryoSat-2 radar altimeter, and assess these together with in situ observations to derive the East Antarctic sea-ice thickness distribution. To do so, information on snow depth over the sea ice will also be quantified.
Robust estimates of Antarctic ice sheet melt
Project 3: Ice Shelves
Ocean-driven Antarctic mass loss is a large source of uncertainty in future sea level rise. To date, there has been no broad-scale comparison and evaluation of mass loss predictions from ocean-ice sheet interaction models. This project will analyse data from a range of circum-Antarctic ocean models, assessing their performance in matching observed ice-shelf melt rates over a range of spatial and temporal scales, with a first focus on the Amery Ice Shelf that has been substantial Australian-based focus of research over the last two decades. This project will contribute to the WCRP-supported Realistic Ice-sheet/Ocean State Estimates (RISE) project.
This PhD project will build on initial data collation and analysis undertaken under RISE by an AAPP postdoc. Beyond simply examining where models agree and disagree, this project will:
- Incorporate a broader dataset to assess the impact of oceanographic context on model performance
- Assess whether the models agree in trend and variability of melt and develop new understanding of the sensitivity of melt to ocean forcing.
- Provide robust evaluation against observational data from both satellite and in situ methods (e.g. autonomous radar)
The candidate will develop skills in data handling, spatial and statistical analysis. A successful completion will improve our ability to assess the models used to predict future sea level rise.
Modelling climate change impacts on Antarctic ecosystems using an end-to-end ecosystem model
Project 7: Krill & Ecosystems
Antarctic marine ecosystems provide ecosystem services that are important on a global scale, and there is a strong imperative to understand and predict the responses of these systems and services to current and future climate change. Atlantis is a 3D, spatially explicit trophodynamic ecosystem model that integrates biology, physics, chemistry, and human impacts (e.g., the effects of fishing on ecosystem structure) to provide a synoptic view of marine ecosystems. An implementation of the Atlantis end-to-end ecosystem model has been developed through collaboration by partner-agencies AAD and CSIRO (though the previous ACE CRC) led by Dr Melbourne-Thomas. This East Antarctic model focuses on the Australian Antarctic Territory and adjacent East Antarctic sector of the Southern Ocean. The model inputs are assembled, and the model is running but requires calibration and deployment for scenario evaluation and validation. This model represents a powerful tool to look at across-food web responses to simulation of altered Southern Ocean conditions. This project is closely aligned with the Antarctic Science Strategic Plan, addressing key research areas that aim to understand sea ice – ecosystems interactions and to determine impacts of physical and chemical change on primary and secondary producers.
Geophysical exploration of the stability of the Larsen C Ice Shelf, Antarctic Peninsula
Project 3: Ice Shelves
Modelled projections of the contribution of the Antarctic ice sheets to sea level rise over this century vary from a few centimetres to more than one metre, a huge uncertainty grounded in poor understanding of ice shelves, the ice-sheet’s floating extensions that constrain its flow from the interior to the ocean. Half of the Antarctic coastline is fringed by such shelves, and many are vulnerable to climate-driven retreat, with some already disintegrated such as Larsen B, Antarctic Peninsula. The latter’s final demise triggered a multi-fold acceleration of its former tributary glaciers that persists to the present day, clearly demonstrating the fundamental role that ice-shelf buttressing plays in regulating sea level rise. The processes driving and resisting ice-shelf retreat are still not well understood, however, including most importantly ice fracture and rift propagation that disrupt the normal assumptions of continuity inherent in ice sheet models and are highly dependent on the heterogeneous nature of ice shelves.
The project “Rift Propagation for Ice Sheet Models” (RIP-ICE), funded by the UK’s Natural Environment Research Council and led by the co-supervisors, will collect new field and satellite data to quantify heterogeneity and develop a fracture physics approach to simulate rift propagation through the Larsen C Ice Shelf, Larsen B’s southern neighbour increasingly affected by climate warming. This PhD project will use cutting-edge quantitative techniques to analyse and model both new ground-penetrating radar, seismic and electromagnetic geophysical data to be collected by RIP-ICE on the Larsen C Ice Shelf in the 2022/23 season, and comprehensive existing geophysical data sets collected in three previous field seasons. Mapping and quantifying the ice-shelf’s internal heterogeneity, including the effects of melting and refreezing that are now prolific throughout much of the year, this PhD project will therefore provide important boundary constraints for the new-generation ice-sheet model developed by RIP-ICE.
How do standing meanders brake the Antarctic circumpolar current?
Project 4: Oceans
Changes in the Southern Ocean are substantial and widespread (Bindoff, Cheung et al. 2019) and different to other regions (Meredith, et al 2019). In particular the winds have strengthened, water masses have changed, and oxygen has declined. New dynamical understanding and observations have shown that there are several hotspots of high poleward heat transport from eddies towards Antarctica (Foppert et al, 2017). These hot spots of eddy driven poleward heat flux are associated with standing meanders tied to large bathymetric features (Thompson and Naviera-Garabato, 2014). The observed increase in kinetic energy (and poleward heat flux) is in contrast to the fact that the transport of the ACC has remained almost constant (Hogg et al, 2014).
While standing meanders occur in the vicinity of large bathymetric features, the dynamics controlling the length, amplitude, and variability of these meanders remains largely unknown. The circulation associated with standing meanders plays an important role in determining the strength and transient response of the Antarctic Circumpolar Current, and the ventilation of fluid in the abyssal ocean and poleward heat transport (Thompson and Naviera-Garabato, 2014). Given the crucial role played by standing meanders and related circulations it is now urgent that we understand how these meanders will respond to changing winds and surface buoyancy forcing, at weather and climate time scales.
The significance of this project relates to the role of standing meanders as a focus for changing poleward transports of heat and the how this heat transport could accelerate with changing climate, with consequences for the redistribution of heat within the polar gyres and the future melt of the Antarctic Ice Sheet. The response time of meanders to changes in surface forcing has widely ranging estimates (eg Armour et al, 2017) and new estimates of response time is a key outcome of this project.
Cross-shelf heat transport in the Denman region of Antarctica: pathways, processes, and impacts
Project 4: Oceans
Glaciers in the Denman region have been melting rapidly over the last few decades. The melting is believed to be driven by the transport of warm Circumpolar Deep Water onto the shelf and toward the glaciers. The Antarctic Slope Current (ASC) and associated strong lateral density gradient pose a barrier to the heat transport in this region. The heat transport across the barrier is accomplished by eddies, tides, and the variability of the ASC. The efficiency of these processes at transporting heat and the associated heat pathways are expected to be sensitive to details of bathymetry in this region (e.g., continental slope, canyons, abyssal hills) which are poorly known from direct soundings. Bathymetry products available for this region, mainly based on satellite measurements and various inversion techniques, show significant differences at a range of scales across various bathymetry products. Processes and pathways for the heat transport and how they are controlled by bathymetry remain to be investigated.
This project will address some of the gaps in our understanding of the processes that regulate the heat transfer from the deep ocean to the continental shelf in the Denman region. A suite of perturbation experiments with a novel high-resolution regional model will be used to quantify the cross-shelf heat transport and heat pathways.
Investigating drivers of variability in the formation circulation of Antarctic Bottom Water
Project 4: Oceans
Antarctic Bottom Water – the densest and most voluminous water mass in the world – has a far-reaching influence on global climate. Formed in the southernmost limb of the global overturning circulation, it stores heat and carbon in the abyssal ocean for centuries and is the main source of oxygen to most of the deep ocean. The slowdown of Antarctic Bottom Water formation, manifesting as abyssal-ocean warming in recent decades, implies changes of global significance as less heat and carbon are sequestered in, and less oxygen is supplied to, the deep ocean. Yet, it remains one of the most difficult water masses to monitor due to winter sea ice cover and the abyssal depths at which it exists. The ACCESS-OM2-01 ocean-sea ice model is the only model known to accurately represent the formation and export of Antarctic Bottom Water.
This project investigates changes in properties, circulation, and mixing of Antarctic Bottom Water – filling the gap in understanding physical processes driving deep ocean variability – in unprecedented detail by comparing output from a state-of-the-art ocean-sea ice model to year-round, full-depth, in-situ Deep Argo float observations in the Australian-Antarctic Basin. This project will also determine the response of Antarctic Bottom Water formation and export to future climate scenarios using the ACCESS-OM2-01. Model runs mimicking expected future climate states, e.g. stronger and southern-shifted westerlies over the Southern Ocean to represent a strengthened Southern Annual Mode and increased surface freshwater fluxes on the shelf to represent increased glacial melt, will isolate specific drivers of variability in AABW formation. The ACCESS model also simulates ocean biogeochemistry, allowing for a parallel investigation into the impact of future climates on carbon uptake in the ocean.