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- Title
The Turbulent Structure of the Azores Current System: A Statistical Analysis.
- Authors
Silva‐Fernandes, S. M.; Peliz, A. J.
- Abstract
Twenty‐five years of satellite altimetry Sea Level Anomaly (SLA) and SLA‐derived eddy trajectories are used for a thorough characterization of the Azores Current (AzC) eddies' kinematic properties (i.e., amplitude, radius, and swirl velocity) and evolution above the Mid Atlantic Ridge (MAR) and the Seewarte seamount chain (around 28°W). Changes in the mean flow kinetic energy and eddy kinetic energy (EKE) along the AzC main axis (around 34.2°N) allow to divide its zonal structure into three sectors: The western one, between the MAR and 28°W, the central, until 24°W and the eastern, between 24°W and 20°W. A clear intensification of the western sector is visible in both distribution maps, as well in the median, Skewness, and Kurtosis of the SLA field. Two main patterns of the SLA turbulent field also emerge from the statistical analysis: a meridional asymmetry around the current mean axis and a zonal one. The kinematic properties of the detected eddies clearly demonstrate that cyclones are more intense and non‐linear than anticyclones, mainly in the western region, exhibiting higher values of EKE. High amplitude cyclones reported in several papers of the area (with a time‐mean amplitude above 16 cm) are rarities, with only six cyclones detected in the 25 years of data. Plain Language Summary: The Azores Current (AzC) is an unstable jet whose evolution leads to the formation of large eddies. Oceanic eddies have an important impact on the transport of physical and biological properties across long distances. Their evolution is however constrained, not only by the interactions between themselves, but also by topography, often leading to their dissipation. In this work, using 25 years of sea level anomaly data, we make a thorough characterization of the AzC eddies and their evolution when passing over the main topographic features in the region: The Mid‐Atlantic Ridge and the Seewarte seamount chain. Cyclonic eddies are intensified in the region between the two mountain systems and are more intense than anticyclonic ones. The large cyclones described in literature are rare events, in fact. Key Points: Cyclonic structures are clearly more intense, presenting higher amplitude, swirl rotation, eddy kinetic energy (EKE), and exhibiting higher non‐linearityA topographic control exists in the western sector, expressed by high values of geostrophic kinetic energy, EKE, and passage of high amplitude structuresHigh amplitude cyclonic eddies referred in the literature are rare, with only six eddies detected in the 25‐year period
- Subjects
SEA level; OCEAN dynamics; MARINE geophysics; OCEAN circulation; QUANTITATIVE research
- Publication
Journal of Geophysical Research. Oceans, 2020, Vol 125, Issue 11, p1
- ISSN
2169-9275
- Publication type
Article
- DOI
10.1029/2020JC016327