Mesoscale structure of the mean East Australian Current System and its relationship with topography

摘要

We document the mean circulation of the East Australian Current (EAC) System, which is the major western boundary current in the southwest Pacific Ocean. A new high-resolution climatology of the region (CSIRO Atlas of Regional Seas, CARS) is used to produce regional fields of steric height and sections of geostrophic velocity. The realism of these fields has been enhanced by the high spatial resolution, allowance for bathymetric control and the influence of land barriers. The increased detail in the maps and sections reveal the major influence that the complex regional topography has on the circulation. The results also provide the appropriate resolution for comparison with recent model studies of the region. We have been able to both resolve well-known features with greater detail and identify previously unrecognized aspects of the circulation. Important results include: (1) The zonal inflow north of 30°S breaks into a series of individual jets after flowing through the island chains as suggested by recent model results. (2) The interaction of the zonal inflow with the local topography as it undergoes bifurcation is documented. (3) A detailed picture of the evolution of the EAC at the western boundary is presented, including surface currents and transports. (4) Separation and recirculation of the EAC within the Tasman Abyssal basin are shown to occur as a double cell structure constrained by bathymetry. (5) The EAC outflow is resolved as a series of eastward, and northeastward currents. (6) The path of the Tasman Front is defined as it interacts with the Tasman Ridge systems. (7) A quasi-permanent eddy is identified for the first time adjacent to the Norfolk Ridge, northwest of New Zealand.