Investigation of the Benguela upwelling eddies using Lagrangian modeling methods

Abstract

In this research, we utilize AVISO altimetry data, the GLORYS12V1 product, and the META3.2 DT Atlas to investigate the Benguela upwelling. By combining these three datasets, we explore the propagation of mesoscale eddies generated within the upwelling zone and examine the dispersion of particles originating from the upwelling zone. The geographical scope of our analysis is confined to the region between 10–36°S and 0–20°E. We employ Lagrangian analysis and the AMEDA approach to study the eddies formed in the upwelling zone. The diverse methods applied enable us to track the movement of upwelling fluid elements in the specified area. The identification of the upwelling zone relies on temperature and salinity gradients in the coastal region. The primary focus of this study revolves around mesoscale eddies emerging in the upwelling zone. We scrutinize the trajectories of cyclones and anticyclones as they propagate westward from the upwelling zone, highlighting variations in the number of upwelling-origin particles within these eddies. We observe distinctions in the locations of upwelling cells between cyclones and anticyclones. Our results indicate that among mesoscale eddies generated in the upwelling zone cyclones predominate. We show that Lagrangian particles, leaving the upwelling zone, propagate throughout the area under consideration. For these particles, we can determine the travel time from the upwelling zone from 1 to 365 days and distances of 500 km for cyclones and 300 km for anticyclones. We found that cyclones are more stable structures with a longer lifetime and with a longer distance traveled in contrast to anticyclones. We believe this is a distinctive feature of the eddies with upwelling origins in comparison with other mesoscale eddies in the area. Finally, we analyze the change of water properties inside the eddies after they leave the upwelling zone and show a significant renewal of vortex cores occurring after 1–2 months of their life.