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 clea rly revealed the existence of a cyclonic (anticlockwise) gyre with imp lied circulation velocities of 0.05 m s(-1) and rotation time of about 10-15 days. Residual current vectors from ship-borne ADCP records ext racted with the assistance of a numerical tidal model also showed cycl onic circulation in the region. The observed circulation pattern is co nsistent 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.