A note on the continuance of the somali eddy after the cessation of the southwest monsoon

Near synoptic observations off the Somali coast using expendable bathythermographs indicate that the large eddy located in the northern Somali Basin which developed during the SW monsoon, could still be identified during the following Northeast monsoon. The offshore (towards the East) geostrophic volume transport is decreasing from 26 x 10 m /sec. in October to 7 x 10 m 3 /sec. in December. Oceanol. Acta, 19Rl, 4, 1, 7-9. RÉSUMÉ Note sur la continuité du tourbillon des Somalis après la fm de la mousson de Sud-Ouest. Des observations presque synoptiques, effectuées au large de la côte des Somalis à l'aide de bathythermographes perdables, indiquent que le grand tourbillon situé au nord du bassin des Somalis qui se développe pendant la mousson de Sud-Ouest, peut encore être identifié pendant la mousson suivante de Nord-Est. Le volume du transport géostrophique vers le large (vers rEst) décroît de 26. 10 m /s en octobre à 7.10 m 3 en décembre. Oceanol. Acta, 1981,4, i, 7-9. Near synoptic observations off the Somali coast during · the beginning of the Northeast monsoon toward the end of 1978 from the French R/V "Jean Charcot" and Exxon tanker "Esso Wilhelmshaven", using expendable bathythermographs (XBTs), indicate that the large eddy (Bruce, 1979) located in the Northern Somali Basin which developed during the previous Southwest monsoon, could still be identified and mapped (Fig. 1). Surveys during the Southwest inonsoon within the last twenty years reveal that large eddies develop during June-September, but it is not certain after the cessation of the SW monsoon winds what decay rate can be attributed to the eddies. From a number of hydrographie observations and current measurements at the end of the NE monsoon in February-March 1965, Bruce and Volkmann (1969) found evidence for a large subsurface Woods Hole Oceanographie Institution Contribution No. 4600. 7 eddy (maximum velocities were at 400 rn depth) located in the Northern Somali Basin. They suggested that this deeper circulation might have been associated with the eddy which had developed during the preceding Southwest monsoon in the upper layers and became increasingly deep as the season progressed. The velocity field in the upper 200 rn by this time (February-March) was relatively weak, and there was no clearly discernable eddy structure, suggesting a downward transfer of momentum during the time since the end of the Southwest monsoon. The temperature sections (Fig. 1) from "Jean Charcot" and "Esso Wilhelmshaven" using relatively closely spaced XBT stations ("' 20-30 km between stations) between 20 November-2 December 1978 show the eddy center to be located between about 9°N-l0°N. The J. G. BRUCE. M. FIEUX, J. GONELLA