SUBDUCTION OF CENTRAL WATER NEAR THE SUBTROPICAL FRONT IN THE SOUTHERN TASMAN SEA

Station data from the Subtropical Front in the southern Tasman Sea obt ained during the summer of 1988/89 were used to determine formation re gions and formation history of Western South Pacific Central Water (WS PCW). At densities of sigma(t) = 26.6 and higher WSPCW found in the so uthern Tasman Sea is formed east of Tasmania near 150-degrees-E, from where it is advected eastward by the general oceanic circulation. No i ndication for equatorward movement after subduction was observed. At d ensities less than sigma(t) = 26.6 the water is characterized by multi ple layers, intrusions and inversions. It is argued that they result f rom variability in Ekman transport direction and Ekman pumping. An atm ospheric boundary layer model is used to estimate Ekman pumping veloci ties from the observed wind field. Ekman pumping velocities and hydrog raphic properties indicate that the less dense water moves equatorward and is subjected to winter mixing north of the investigation regin, b efore it obtains its final temperature-salinity properties and becomes part of WSPCW through subduction.