Recent Observations of the Alboran Sea Front

摘要

Four sets of observations were obtained in the western Mediterranean Sea during the period November 1976 to April 1977 in order to study the structure and seasonal variability of the Alboran Sea Front. The data were gathered from USNS KANE and consist of 217 XBT's (expendable bathythermographs) and 28 SV/STD (sound velocity-salinity-temperature-depth) stations. These data, together with previous observations in spring and summer, indicate that the Alboran Sea Front is a persistent feature throughout the year. It meanders from Gibraltar eastward through the basin, establishing a series of alternating anticyclonic and cyclonic gyres. The front is confined to the upper 200 m and has a typical width of 50 km. Strongest horizontal temperature gradients (0.1 deg C per km) are found in summer and fall when the net change across the front is 5-7 deg C; salinity undergoes a corresponding 2 ppt change. Strongest gradients of sonic layer depth and sound channel depth occur in winter when both parameters change 200 m across the front. The anticyclonic gyre of warm water in the western Alboran Sea has a diameter of 75 to 100 km and appears to be permanent. When cool water upwelled along the southern coast of Spain is entrained into the gyre, the main features of the Alboran Sea circulation are enhanced and can be clearly seen in satellite infrared images.