The separation of the East Australian Current:
A Lagrangian approach to potential vorticity and upstream control
Random subset of 80 particles advected in the ocean model following (left) the pathway of the extension of the EAC and (right) the pathway of the Tasman Front, following their release at 27S. Particles traveling through box A are selected to form the extension of the EAC. Particles traveling through box B form the pathway of the Tasman Front.
East of Australia, a warm and saline boundary current flows along the coast. This western boundary current is the East Australian Current (EAC), also known from the movie ‘Finding Nemo’. This watermass plays an important role for biological processes all along the east coast of Australia. However, at approximately 34°S, it separates from the coast. Part of the watermass flows eastward along the Tasman Front and part forms the extension of the EAC flowing south (see Figure).
In this paper, the EAC watermass is traced to gain new insights into why this current separates from the coast. The results show that the ‘fate’ of the watermass is already determined by its depth distribution upstream of the separation latitude. The separation and pathways are controlled by the structure of the isopycnals in this region. It is shown that anticyclonic eddies play a key role in separating the watermass, as they occasionally push isopycnals down to allow the EAC watermass to travel further south.