Mesoscale dynamics of an intrathermocline eddy in the Canary Eddy Corridor
Abstract. High-resolution observations of an intrathermocline eddy were conducted in November 2022 within the Canary Eddy Corridor. Formed in early summer 2022, this mature mesoscale eddy exhibited a 550 m vertical extent, with its core centered at 110 m depth, and a segmented horizontal structure with a 25 km inner core radius surrounded by a 55 km-wide outer ring. Propagating southwest at 4.7 km·day−1, its motion aligned with the phase speed of a first-mode baroclinic Rossby wave. Its rotational dynamics featured a 3.9-day inner core rotation period shaped by stratification, which created distinct rotational layers. Rossby number (-0.5) and potential vorticity (∼ 10−11 m−1·s−1, 90 % less than its surroundings) metrics revealed a core regime dominated by planetary rotation and strong homogeneous water mass isolation, while Burger numbers (length-scale: 0.16; energy-based: 0.68) emphasized the role of stratification and buoyancy forces in shaping its structure. The eddy carried available heat and salt anomalies of 7.052 EJ and 0.016 Tkg, driving heat and salt (freshwater equivalent) fluxes of 5.13 TW and 0.47 Gkg·s−1 (-0.013 Sv), underscoring its significance in transporting coastal upwelling waters into the ocean interior. The intrathermocline nature of the eddy developed during the growth phase, and was shaped by surface convergence enhanced by upwelling filament interactions, followed by isopycnal deepening offshore. Throughout its year-long lifespan, the eddy experienced intrinsic instabilities and eddy-to-eddy interactions, culminating in its decay by early summer 2023. The distinct properties of this eddy, alongside the apparent variability of similar features in the Canary Eddy Corridor, underline the need for expanded high-resolution studies, including comprehensive observational efforts and advanced numerical simulations, to better understand their role as zonal pathways for heat, salt, and potentially biogeochemical properties within regional ocean circulation.