Dynamics of a marine heatwave: what happens below the surface?

Extreme temperatures in the ocean are getting more frequent and intense, impacting marine ecosystems and industries. However the subsurface signature of these marine heatwaves is still largely unknown, in particular in shallow coastal areas where most of the ecological damages occur.

In addition to sustained observations, the Australian Integrated Marine Observing System (IMOS) now aims at sampling the coastal ocean during marine heatwaves with real-time deployments of ocean gliders. Gliders are automated underwater vehicles which measure the water properties between the ocean floor and the surface for a few weeks. Two of such deployments were successfully finalised, sampling the eastern shelf of Tasmania during the latest marine heatwave event in the Tasman Sea in summer / spring 2019.

The project aims at understanding the extent and characteristics of marine heatwaves using glider measurements and complementary satellite and moored observations. Key questions include the temporal evolution, from the onset to the decline of the extreme event, and the influence of the local oceanography such as currents and wind-driven processes on the persistence and variability of these anomalous temperatures. The student will use programming language to analyse this unique dataset and compute the heat budget equations.

Basic knowledge of oceanography and experience in Matlab or Python are required. The project will be based at UNSW Sydney, co-supervised by Amandine Schaeffer (UNSW), Jessica Benthuysen (AIMS) and Neil Holbrook (UTAS).

Contact: a.schaeffer@unsw.edu.au

Understanding how precipitation extremes scale in future climates

While global climate models (GCMs) remain our best tool for investigating the Earth’s system response to anthropogenic forcings, their spatial resolution (generally hundreds of km) is much coarser than the scales of the key processes leading to precipitation extremes (e.g. intense convective rainfall events). Therefore, parametrizations are necessary and the simulation of precipitation is not explicitly resolved in models. Spatial resolution is finer in regional climate models (RCMs) (generally tens of km), which is expected to improve the simulation of precipitation extremes that are very sensitive to spatial contrasts and topography. However, even at the scales of regional models parametrizations are still required.

Global and regional models have advantages and disadvantages for studying precipitation extremes, but how their output scales with respect to the other is rarely compared. In particular, it is unclear how the future changes in precipitation extremes from large ensembles of regional climate models compare to those from global models. This project will assess how precipitation projections for Australia from global and regional models scale using the latest start-of-the-art GCMs and RCMs.

Requirements: Some prior programming and data visualisation experience (e.g. Python, NCL, MATLAB, R, etc.).

This project is supervised by A/Prof Lisa Alexander and Dr Margot Bador (UNSW Sydney). Please contact l.alexander@unsw.edu.au for more information.