Use of SAR data to Monitor the Greater Agulhas Current

Abstract

The strong and dynamic greater Agulhas Current is known to have significant influence on the local marine environment and ecosystem. It is also considered to play an important role in the global thermohaline circulation, notably due to the transport of heat and salt from the Indian Ocean into the South Atlantic Ocean. Regular monitoring of the dominant processes and variability within the greater Agulhas Current is thus highly needed. Recently Doppler- derived ocean surface velocities from the European Space Agency’s (ESA) Envisat Advanced Synthetic Aperture Radar (ASAR) have demonstrated abilities to manifest the intensity of surface currents. In this paper the regular direct surface velocity estimates of the greater Agulhas Current from the ASAR since summer of 2007 are presented. These estimates are assessed by direct comparison to other independent estimation of the surface current in the greater Agulhas current obtained from surface drifter data, radar altimetry and an ocean circulation model. The results are promising and highlight that the Doppler-based ocean surface velocity retrieval offers a new innovative approach to monitor and advance the understanding of the dynamic processes of the greater Agulhas Current.