THE STRUCTURE OF THE WIND-DRIVEN CIRCULATION IN THE SUBTROPICAL SOUTH-PACIFIC OCEAN

The structure of the wind-driven circulation in the subtropical South Pacific is studied using simple diagnostic and analytical models. The diagnostic calculation is based on the Levitus climatology. The analyt ical model is forced by observed winter mixed layer density and depth calculated from the Levitus climatology and by the surface wind stress data from the Hellerman and Rosenstein climatology. The wind-driven g yre in the South Pacific is relatively deep, reaching 2.4 km along the southern edge of the gyre. The gross feature of subduction obtained f rom both the data analysis and the analytical model is similar, with a n annual ventilation rate of 21.6 Sv (Sv = 10(6) m(3) s(-1)), includin g 18.1 Sv from vertical pumping and 3.5 Sv from lateral induction. Alt hough the annual subduction rate in the South Pacific is comparable to that in the North Atlantic, lack of localized subduction leads to rel atively weak mode water formation in the region where the East Austral ian Current separates from its western boundary. In addition, results from the analytical model indicate the existence of an isopycnal slope reversal in the southeastern Pacific.