Deep water mass circulation in the Alboran basin: measurements - January to April '82 ALBORAN II
Alboran Sea circulation between 220 m and 1100 m depth is studied. Interaction between three water types, Atlantic water, Levantine water, and western Mediterranean Deep water cause a complicated flow pattern. Atlantic water flowing as a jet through the Strait of Gibraltar forms a variable anticyclonic gyre down to a depth of 200 m. A few works based on geostrophic calculations and the Bernoulli equation treat the deep flow. The measurements by moored current meters and free-floating vertical current meters deployed and acoustically tracked in the western part of the Moroccan continental slope revealed an enhanced current along this slope toward Gibraltar. The study of the total deep circulation pattern in the Alboran basin used a combination of current meter and free float measurements. The tracks of the floats at all depths from 220 m to 1100 m revealed broad and slow (approx. 2.5 cm/s) cyclonic circulation located under the surface anticyclonic gyre. Floats revealed the boundary current along the Moroccan continental slope to have a more complicated pattern, moving eastward or westward after reaching the slope east or west of 4.0deg W respectively Current-meter data generally agreed with these results. The time-dependent vector field of currents created from all of the float and current-meter readings shows periods of enhanced and extended cyclonic motion followed by stagnation and even reversal of current direction in external positions, with only the small cyclonic vortex. The satellite and conductivity-temperature-depth (CTD) data indicated the existence of an anticyclonic gyre with variable extension into the south-western part of the Alboran during the experiments. Considerable upward bending of isolines across the Moroccan continental slope was visible, but the lateral extension and the depth of the anticyclonic circulation do not agree with the existing explanation in the literature. Integrated atmospheric pressure over the western Mediterranean and the Alboran Sea did not correlate with the currents.