Statistical analysis of the surface circulation in the Algerian Current using Lagrangian buoys

The Algerian Current (AC) is one of the most energetic flows in the Mediterranean basin. A characteristic picture of this current is formed by a series of mesoscale eddies at different scales. Here, statistical analysis of 15 surface Argos buoy tracks in 1996–1997 provides a complete Lagrangian view of the AC. The buoys, released upstream and across a coastal meander between 0°E and 1°E longitude, were followed for 3 months. They travelled eastward at an average speed of 14 cm/s and showed high energetic fluctuations related to several mesoscale eddies. The characteristic integral time and space scales are highly anisotropic. For the zonal component, these are about 4 days and 66 km, and for the meridional component, about 2 days and 26 km. Representative values of effective diffusivities from single dispersion statistics are within 0.7–1.3×108 and 1.5–6.0×107 cm2/s for the zonal and meridional directions, respectively. A local analysis shows that mesoscale motions are particularly relevant in the region 1–3°E and 7–8°E, provided the considerably high values of eddy kinetic energy in comparison with the mean kinetic energy. Eddy–mean current interactions are evidenced by the significant changes of sign of horizontal covariance from west to east. Finally, an Eulerian picture of the AC is built, exhibiting similar trends than previous and recent field observations.