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Evolution of the open-sea eddy ALGERS'98 in the Algerian Basin with Lagrangian trajectories and remote sensing observations
de Jesus Salas, J. (2003). Evolution of the open-sea eddy ALGERS'98 in the Algerian Basin with Lagrangian trajectories and remote sensing observations. J. Mar. Syst. 43(3-4): 105-131. dx.doi.org/10.1016/j.jmarsys.2003.08.001
In: Journal of Marine Systems. Elsevier: Tokyo; Oxford; New York; Amsterdam. ISSN 0924-7963, more
Peer reviewed article  

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Keywords
    Altimeters; Eddy kinetic energy; Infrared imagery; Lagrangian current measurement; Mediterranean [Marine Regions]; Marine

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  • de Jesus Salas, J.

Abstract
    The westward evolution of an open-sea anticyclonic eddy along the western Algerian Basin is shown, for the first time, by means of 15 buoy trajectories and remote sensing observations. For not, vert, similar3 months, the buoy trajectories described several anticyclonic loops in periods of 4–21 days. The eddy's movement, translation, and rotation were separated with a kinematic model, resulting in a mean translation speed of not, vert, similar2 km/day, which fits the self-propulsion speed predicted on theoretical models for isolated eddies on a beta plane. Fluctuations in translation speed were associated with advection of the mean flow and topographic interactions. Both mechanisms changed the eddy's horizontal shape from circular to elliptical, inducing fluctuations in its swirl velocity and solid-body rotation. The initial stage of the eddy is an isolated asymmetric dipole, comprised by a small cyclone and a large anticyclone, the latter generated from a frontal instability, which under the Coriolis term acquires anticyclonic relative vorticity. During its first days of life, the anticyclonic eddy was shallow Ro=0.9 and small (diameter less than 50 km). Later on, it reached a diameter of not, vert, similar150 km and a vertical structure of 3 km (Ro=0.1). A retrospective analysis with infrared images shows that the eddy's generation took place at about 3–4°E. Then, the eddy completed a counterclockwise circuit never before reported in other studies and ended up at the entrance of the Algerian Basin, where the interaction with the topography and the coastal instability induced its decay. The eddy's life span was not, vert, similar10 months. Computations of the heating rate following clusters of buoy trajectories show fluctuations throughout the eddy's journey, induced by advection and a seasonal warming.

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