Long-lived mesoscale eddy populations in contrasted dynamical environments around the Canary Islands

Abstract

Mesoscale eddies are recurrent features in the Canary Islands region, where the interaction between the Canary Current, the islands topography, and the nearby North African coastal upwelling is associated with a complex variety of vortices. Despite decades of regional studies, the relative importance, spatial differentiation, vertical structure, seasonal variability and persistence of the different eddy populations remain poorly quantified. The aim of this work is to provide the first long-term and consistent evaluation of the main eddy populations associated with contrasted dynamical environments in the region, offering a systematic distinction between vortices associated with island– and upwelling–current interactions, by analyzing the formation, evolution, and dynamics of eddies generated over the period 1993–2022. Using satellite altimetry from the META product and three-dimensional structure data from ARMOR3D, eddies were grouped according to their rotation (cyclonic or anticyclonic) and their formation within island-wakes or upwelling-front dynamical environments, enabling a comparative characterization of their properties. Results show that anticyclonic eddies represent a larger fraction of the detected long-lived mesoscale eddy population (approximately 56% over the 30-year study period) and, on average, exhibit greater abundance, persistence, and energetic intensity than cyclonic eddies, with larger amplitude, radius, and mean velocity. Seasonal variability strongly modulates eddy generation and persistence, particularly for upwelling-front eddies. Vertical temperature, salinity, and geostrophic velocity distribution reveal that anticyclones have deeper and more coherent cores, with higher surface velocities, reinforcing their role as the most structurally robust eddies in the region. By explicitly separating eddy populations associated with different dynamical environments, this study shows that mesoscale eddies commonly treated as a single population exhibit fundamentally different dynamical, energetic, and vertical structures, highlighting the importance of a population-based classification linked to contrasted dynamical environments. These findings provide the first systematic comparison of eddy populations in the Canary Islands region, emphasizing their importance for the transport of physical and biogeochemical properties in the eastern subtropical North Atlantic.