THE EDDY FIELD ASSOCIATED WITH THE AZORES FRONT EAST OF THE MID-ATLANTIC RIDGE AS OBSERVED BY THE GEOSAT ALTIMETER

Two years of Geosat data (November 1986 to December 1988) for the Azor es-Madeira region of the North Atlantic are analyzed. The objective is to study the eddy field associated with the terminal retroflection of the Azores current. The rms variability of sea level anomaly is 4 to 8 cm, with maximum values between 33-degrees and 35-degrees-N being as sociated with the Azores current and located on its northern flank. Hi gher energy is observed during winter and during the year November 198 7 to November 1988. Analysis of velocities at crossovers reveals aniso tropy with larger meridional velocity variances. This is the signature of meanders and/or eddies elongated in the north-south direction. The eddy-mean flow interaction is studied through the analysis of the Rey nolds tensor. Meridional and zonal accelerations of the mean by the ed dy field are consistent with retroflection of the Azores Current to th e south and to the west. Spectral analyses show that the dominant sign als have periods and wavelengths larger than 100 days and 300 km, resp ectively. Propagation velocities are westward but slow (1.5 km/d). Syn optic mapping of the eddy field shows the wavelike structure of the va riability on the northern flank of the current. It is likely that the wave generation is not directly due to an instability of the Azores cu rrent but is attributable to a cause more to the east. Once formed, th e wave interacts with the current in winter and forms meanders. Season al variations of the surface circulation are finally analyzed from the 2-year-long time series of synoptic maps. There is a clear seasonalit y in the surface circulation which generally appears to be consistent with historical in situ measurements. In winter there is a strong mean dering and a southward branching, while in summer the mean front is na rrower and penetrates further to the east.