Direct observations of the East Australian Current and Property Transport at 27 oS from 2012-2013

The East Australian Current (EAC) is the complex and highly energetic poleward western boundary current system of the South Pacific subtropical gyre. It is the dominant mechanism for the redistribution of heat between the ocean and atmosphere in the Australian region by transporting heat from the tropical Pacific Ocean to the mid-latitude ocean and atmosphere. While previous work, using the available observations and ocean models, have documented long-term trends and variability of the EAC and suggested a link between the EAC variability with the large-scale Pacific gyre forcing, an understanding of the full-depth EAC property transport and its temporal variability is far from complete. What is lacking is a sustained time-series of full-depth property observations of the boundary flow of the EAC across its entire offshore extent and of sufficient duration to resolve seasonal, interannnual and decadal signals.The only existing data is from a 2-year mooring array at 30 ^oS maintained during WOCE. However, this mooring array was only 120-km wide and the complete extent of the EAC system was not resolved. This was compounded by the fact that the array was located within the most energetic portion of the EAC eddy field.

To fill this observational gap the Australian Integrated Marine Observing System (IMOS) deployed a full-depth current meter and property (temperature and salinity) mooring array from the continental shelf to the abyssal waters across the EAC at approximately 27 ^oS. The initial EAC transport monitoring array was deployed from April 2012 to August 2013. The mooring array consisted of 7 moorings ranging in water depth of 200 m to 4797 m.

This presentation will discuss the EAC mean mass and heat transport and its temporal variability from the analysis of the mooring array. The sustained monitoring of the EAC is central to our understanding of how climate signals are communicated through the global ocean. These observations will improve our understanding the frequency and drivers of the major EAC modes and their impact on the down-stream EAC evolution and interaction with the coastal-shelf currents and EAC separation zone. It is hoped that the joint observation and model study will provide significant insight into the dynamical interactions between the EAC and the basin-scale and local shelf ocean circulation.