Eddy Structure and Dynamics in the Mozambique Channel

Abstract

Abstract The Mozambique Channel circulation is dominated by a sequence of southward migrating cyclonic and anticyclonic eddies and previous studies have been done to investigate the flow, the variability and nature of the currents in the Mozambique Channel and the generation of the Mozambique Channel eddies. This master thesis studies the eddies structure and dynamics, based on data obtained from the 2008 ASCLME-Nansen cruise which includes salinity, temperature, currents, density and oxygen measurements. However, this study is restricted to the northern Mozambique Channel where study areas covering three cyclones and one anti-cyclone were considered. The results indicate the existence of upwelling and downwelling zones placing the thermocline near and far-off the surface, respectively. In addition, the eddies have wavelengths of 500 km, amplitudes of more than 100m and a frequency of occurrence of 4 eddies per year. Previous studies suggested that the frequency with which these eddies are formed may in turn be controlled by Rossby waves travelling zonally across the South Indian Ocean. The Rossby number found in this research, indicates that the flow in the Mozambique Channel can be considered geostrophic. Furthermore, the Rossby deformation radius is nearly 20km m for the cyclone and 25km for the anti-cyclones so that the eddies scale seems to be controlled by the Channel size.