A TRACER STUDY OF THE FORMATION, DISPERSAL, AND RENEWAL OF LEVANTINE INTERMEDIATE WATER

The formation and dispersal of Levantine Intermediate Water (LIW) are examined using a series of tracer experiments based on an eddy-permitt ing general circulation model of the Mediterranean. LIW is formed in t he region of the Rhodes gyre and disperses via both the time-mean and time-varying circulation. Tracer released in the Rhodes gyre is transf erred westward by the time-mean circulation but also southward and eas tward by the time-varying circulation. Off-line tracer experiments sug gest that the time-varying circulation exhibits both advective and dif fusive components, where the advective component opposes downgradient transfer in some regions. The rate of invasion of tracer into the main thermocline suggests that the renewal timescale is 10-20 years for LI W and of order 100 years for Eastern Mediterranean Deep Water. Assumin g advection dominates the transfer of tracer, the implied annual subdu ction rate is 0.6+/-0.1 Sv in the Rhodes gyre and 0.2+/-0.1 Sv in the Adriatic Sea. The LIW mode is found to become cooler and fresher as a result of mixing with the Adriatic outflow, while its potential vortic ity appears well conserved.