Understanding ENSO event modulation of marine heatwaves

Supervisors

• Professor Neil Holbrook (IMAS)
• Dr Xuebin Zhang (CSIRO)

Summary

This project aims to explore and understand how different types of El Nino – Southern Oscillation (ENSO) events modulate marine heatwave events, regionally around Australia and more broadly around the world.

There is clear evidence that marine heatwaves may be modulated by modes of climate variability (e.g. Di Lorenzo and Mantua 2016; Oliver et al. 2017). However, the mechanisms underpinning climate mode influences on ocean temperature extremes are still not well understood. El Nino – Southern Oscillation (ENSO) appears to be a strong modulator of marine heatwave duration and intensity, in particular in the tropics – although connections between ENSO and MHWs is also evident in higher latitudes (e.g. Di Lorenzo and Mantua 2016). With anticipated changes to extreme ENSO in a future climate (Cai et al. 2015), it will be important to better understand the influence of ENSO on MHWs in a changing climate.

Objectives

1. Examine historical observations of sea surface temperature (e.g., NOAA OI SST (since 1982) + HadISST (since 19^th Century)) and ocean reanalysis products (e.g., SODA, GECCO2 and ORA-S4 back to 1960) to look at flavours of ENSO (specifically Central Pacific (CP) versus Eastern Pacific (EP) El Nino and decadal signature of Interdecadal Pacific Oscillation (IPO)/Pacific Decadal Oscillation (PDO)) and their relationship with marine heatwaves (MHWs), to develop a hypothesis of possible mechanisms of how ENSO and decadal climate mode modulate MHWs.
2. Test the above hypothesis by analysing multi-century pre-industrial control simulations, historical simulations and ocean forced experiments in climate models, such as Geophysical Fluid Dynamics Laboratory (GFDL) CM2.1 and/or the Australian Community Climate Earth System Simulator (ACCESS), to understand the mechanisms underpinning the links between ENSO and MHWs
3. Examine climate change projections of MHWs in the future, and whether there are changes of relationships between ENSO and MHWs and their connection with changes in the background climate state, by analysing available climate mode simulations (especially those with higher-resolution ocean component) and CSIRO Ocean Downscaling Experiment (i.e., dynamical downscaling of 21^st Century ocean climate using a 0.1^o ocean model)

Methods

The project will analyse selected high-resolution model simulations, data and reanalysis products (see Objectives above) to characterise the relationships and mechanisms underpinning the modulation of marine heatwaves by El Nino – Southern Oscillation.

Essential skills/experience

• First class Honours degree or equivalent in physical oceanography or atmospheric science, or Masters-degree in same
• Good experience with analysing large spatial and temporal data sets
• Sound programming skills using MATLAB, python or FORTRAN/C++.