ON THE UPPER LAYER CIRCULATION IN THE ALBORAN SEA

We present new experimental results and assemble them with previous re sults in order to develop an improved picture of the upper layer circu lation in the Alboran Sea. It is suggested that the key idea to unders tanding this upper layer circulation is the tendency of the Atlantic j et (AJ) to have negative curvature. Local interactions with the wester n Alboran gyre (WAG) or the African coast can, however, counterbalance this tendency and modify the anticyclonic path of the AJ. It is also proposed that the density gradients in the WAG can be maintained in pa rt by means of an intermittent surface cross-gyre current which result s in an input, mixing, and renewal of Atlantic water. The static stabi lity at the bottom of the gyre increases because of the mixing of Atla ntic water with Western Mediterranean Deep Water which is uplifted clo se to the African coast. This mixing process thereby acts as a local s ource of potential vorticity. We also report the existence in the Albo ran Sea of subsurface anticyclonic eddies (located between 100 and 400 m) of relatively cold water that appear to be detached from the Iberi an shelf. Regarding the large-scale variability of the AJ-WAG system, we present evidence of an eastward migration of the WAG and the subseq uent formation of a new anticyclonic gyre in the western Alboran basin on a timescale of 1 month. This eastward gyre migration process tempo rarily allows the simultaneous presence of three anticyclonic gyres in the Alboran Sea.