Interbasin leakage through Agulhas current filaments

Abstract

The climatologically important exchange of water between the South Indian and South Atlantic oceans takes place mainly through the shedding of rings at the Agulhas Current retroflection. A minor contribution is made by the advection of Agulhas Current filaments into the South Atlantic. Satellite infrared images and hydrographic sections are used to show that Agulhas filaments are present about 56% of the time, are on average 50 km wide and 50 m deep, and carry excess heat of about 3.5 × 10 19 J as well as excess salt amounting to about 1–5 × 10 11 kg into the South Atlantic in each individual filament. Since most of this excess heat will be rapidly lost to the overlying atmosphere, the lasting contribution to interbasin exchange by Agulhas filaments is an annual salt flux of about 3–9 × 10 12 kg. It is thus estimated that Agulhas filaments contribute up to about 15% of the total interbasin salt flux generated by the Agulhas Current.