Voyage Number
IN2019_V05
Voyage Dates
Voyage Location
Chief Scientist
Dr Bernadette Sloyan
Institution
CSIRO
Voyage summary
Research voyage from the continental slope to the abyssal waters off Brisbane to recover and re-deploy an array of six moorings in the East Australian Current (EAC). The EAC mooring array is a component of the Integrated Marine Observing System (IMOS).
The East Australian Current (EAC), a southward flow off eastern Australia, is one of the major global western boundary currents. The EAC is the dominant mechanism for the redistribution of heat and freshwater between the ocean and atmosphere in the Australian region; it is a vital component of the eastern Australian coastal ecosystem.
The EAC mooring array monitors the mass, heat and freshwater transported by the EAC, which is central to our understanding of how climate signals are communicated through the ocean. Moorings are deployed in water depths from approximately 500 m to 5000 m.
This voyage includes two other research projects:
- Dynamics of larval fish diversity for ocean observing off North Stradbroke Island (Prof Iain Suthers, UNSW): Plankton and larval fish will be surveyed to better understand biodiversity and factors that influence productivity in continental shelf waters.
- Argo float deployments (Dr Peter Oke, CSIRO): Four Argo floats will be deployed during the voyage as part of the international Argo float program.
The science team on this voyage includes 31 participants from 4 institutions. The voyage is part of a multi-year project in support of IMOS.
Voyage outcomes
During this voyage, researchers successfully recovered and deployed six moorings in the East Australian Current (EAC) between the continental slope and the abyssal plain off the coast from Brisbane. In addition, 12 CTD (conductivity, temperature and depth instrument)/LADCP (Lowered Acoustic Doppler Current Profile) stations were completed, which will support the moorings in effectively tracking variability of the EAC. Transit periods during the voyage were utilised to conduct 114 plankton tows which will be used to assess the impact of a changing EAC on coastal ecosystems.
The voyage has contributed to the long-term monitoring of the EAC to ensure that vital data on the redistribution of heat, freshwater and biomass is captured. Moorings will monitor ocean changes continuously, which will contribute to high quality regional and coastal models being developed by Australian researchers.
During the voyage, researchers also found that ocean currents travelling southward interacted with coastal waters to creates eddies, spinning vortexes of water. These are also called ‘wobbles’. These wobbles showed increased phytoplankton production (blooms) which scientists found were the result of deeper nutrient rich water being pulled to the ocean surface by the vortex. This is termed an upwelling. These upwellings feed vital nutrients to the ocean surface and were observed to result in phytoplankton blooms over 100 km or more. Phytoplankton are important as they provide the foundation of the marine ecosystem and are food for larger marine animals. Phytoplankton abundance directly affects ocean productivity. See News item below for further details.
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