Subsurface fine-scale patterns in an anticyclonic eddy off Cap-Vert Peninsula observed from glider measurements

• Main Authors: Kolodziejczyk, N., Testor, P., Lazar, A., /Echevin, Vincent, Krahmann, G., /Chaigneau, Alexis, Gourcuff, C., Wade, M., Faye, S., Estrade, P., Capet, X., Mortier, L., /Brehmer, Patrice, Schutte, F., Karstensen, J.
• Format: Text
• Language: English
• Published: 2018
• Subjects: submesoscale; stirring; tropical Atlantic; meoscale eddy; glider; measurements; OMZ; North Atlantic
• Online Access: https://www.documentation.ird.fr/hor/fdi:010074167

Glider measurements acquired along four transects between Cap-Vert Peninsula and the Cape Verde archipelago in the eastern tropical North Atlantic during March-April 2014 were used to investigate fine-scale stirring in an anticyclonic eddy. The anticyclone was formed near 12 degrees N off the continental shelf and propagated northwest toward the Cape Verde islands. At depth, between 100 and -400m, the isolated anticyclone core contained relatively oxygenated, low-salinity South Atlantic Central Water, while the surrounding water masses were saltier and poorly oxygenated. The dynamical and thermohaline subsurface environment favored the generation of fine-scale horizontal and vertical temperature and salinity structures in and around the core of the anticyclone. These features exhibited horizontal scales of O(10-30km) relatively small with respect to the eddy radius of O(150km). The vertical scales of O(5-100m) were associated to density-compensated gradient. Spectra of salinity and oxygen along isopycnals revealed a slope of around k(-2) in the 10- to 100-km horizontal scale range. Further analyses suggest that the fine-scale structures are likely related to tracer stirring processes. Such mesoscale anticyclonic eddies and the embedded fine-scale tracers in and around them could play a major role in the transport of South Atlantic Central Water masses and ventilation of the North Atlantic Oxygen Minimum Zone.