Mesoscale eddy activity in the southern Benguela upwelling system from satellite altimetry and model data

摘要

We characterize eddy activity in the southern Benguela upwelling system with absolute sea level data deduced from remote-sensing measurements and numerical simulations run with a regional model, using a wavelet-based technique for identification and tracking of coherent structures. Statistics on eddy count, size, type and location are obtained along the continental slope of the upwelling system for a common period of interest shared by model and satellite data. We draw a comparison between mesoscale variability calculated by the regional model and ground truth accounted by satellite altimetry. We show that the presence of cyclonic eddies along the upwelling front over the South Benguela slope is recurrent throughout the year. Moreover, the agreement between model and observations is fair and validates the modeling approach. Tracking in the model of volume properties of continental slope, cyclonic eddies on their way toward the open ocean suggests that these eddies play a significant role in coastal-open ocean exchanges. With lifetimes of several months, these eddies can export significant volumes of nutrient-rich waters far from the coastal upwelling.