A high-resolution reanalysis of the East Australian Current System assimilating an unprecedented observational data set using 4D-Var data assimilation over a two-year period (2012-2013). Version 2017.

For the EAC region, we combine a high-resolution state-of-the-art numerical ocean model with a variety of traditional and newly available observations using an advanced variational data assimilation scheme. The numerical model is configured using the Regional Ocean Modelling System (ROMS 3.4) and takes boundary forcing from the BlueLink ReANalysis (BRAN3). For the data assimilation, we use an Incremental Strong- Constraint 4-Dimensional Variational (IS4D-Var) scheme, which uses the model dynamics to perturb the initial conditions, atmospheric forcing, and boundary conditions, such that the modelled ocean state better fits and is in balance with the observations. In addition to the traditional data streams (satellite derived SSH and SST, Argo profiling floats and XBT lines) we exploit newly available observations collected by Australia's Integrated Marine Observing System (IMOS). These include velocity and hydrographic observations from a deep-water mooring array (the EAC transport array, 27.5S) and several moorings on the continental shelf (27.5S, 30S and 34S), surface radial velocities from a high-frequency (HF) radar array (at Coffs Harbour, 30S), and temperature and salinity observations from ocean gliders.