Understanding how fine scale processes underpin interactions between eddies and the exchange of water, heat, and biota in the East Australian Current (EAC) System.
Mesoscale eddies are the “weather systems” of the ocean, retaining and transporting heat, salinity, and other tracers, impacting regional ocean circulation, ecosystems, and climate. Sharp temperature fronts between eddies drive sub-mesoscale processes (~1-10 km) and vertical air-sea fluxes that contribute to storm formation. In the eddy-rich East Australian Current (EAC) System, eddies are penetrating further south as the climate changes, driving ocean warming and “tropicalisation”.
We know little about the physical mechanisms underpinning interactions between eddies and the exchange of water, heat, and biota. The sub-surface dynamics of eddy-eddy interactions remain elusive, particularly near the continental shelf where eddies undergo complex interactions with bathymetry. Eddy-eddy interactions are a key source of uncertainty for both ocean forecasts and storm prediction. Consequently, along the eddy-dominated region of southeastern Australia, oceanic forecasts produced by the Bureau of Meteorology (BoM) have large errors. Accurate forecasts of the marine environment in this region are crucial to BoM’s end-users.
The AUSWOT campaign provided the first observation-based full-depth picture of eddy-eddy interactions and their atmospheric and biogeochemical impacts in the EAC System. A 24-day cruise was carried out in September / October 2023 and 2 NOAA SVP drifters and several Argo and BGC-Argo floats were deployed during the voyage. The field experiments coincided with the pioneering high-resolution SWOT satellite, which provided sea-surface height observations with unprecedented spatial resolution.
The combination of in situ measurements, high-resolution satellite observations, and shore-based modeling efforts are now leading to radical new understanding of the physical and biogeochemical dynamics of eddy-eddy interactions and their predictability. A core output from the cruise was a comprehensive open-access dataset of physical, biogeochemical and atmospheric properties of eddies and their fronts, and methodologies to improve eddy prediction.
Outcomes of the AUSWOT campaign also include new dynamical understanding of eddy-eddy interactions, and improved operational forecasts along Australia’s most populous coastline.
Principal investigators: Moninya Roughan, Jason Evans, Shane Keating, Amandine Schaeffer, Colette Kerry (UNSW Sydney); Gary Brassington, Andrew Dowdy, Eric Shulz (Australian Bureau of Meteorology); Pete Strutton, Christina Schallenberg (University of Tasmania); Paulina Cetina Heredia (Hawaii Pacific University); Dr Alice Della Penna (University of Auckland).
Institutes involved in the campaign: UNSW Sydney, Australian Bureau of Meteorology, University of Tasmania, Hawaii Pacific University, University of Auckland.
Contact point for the study site: Shane Keating (s.keating@unsw.edu.au)