OBSERVATIONS OF A CYCLONIC GYRE IN THE WESTERN IRISH SEA

Nine free-drifting buoys were deployed for a period of 10 days in July 1990 in the western Irish Sea. High resolution buoy trajectories clearly revealed the existence of a cyclonic (anticlockwise) gyre with implied circulation velocities of 0.05 m s(-1) and rotation time of about 10-15 days. Residual current vectors from ship-borne ADCP records extracted with the assistance of a numerical tidal model also showed cyclonic circulation in the region. The observed circulation pattern is consistent with geostrophic surface flow around a static, isolated dome of cold, dense, bottom water which is a repeatedly observed feature of the western Irish Sea summer density structure. It is suggested that the gyre may be important in promoting planktonic larval retention in the western Irish Sea.