THE CIRCULATION OF THE SUBTROPICAL SOUTH-PACIFIC DERIVED FROM HYDROGRAPHIC DATA

The circulation and distribution of water masses of the subtropical So uth Pacific are described, based on salinity and temperature data from two trans-Pacific zonal sections at 32 degrees S and 17 degrees S (Wo rld Ocean Circulation Experiment sections P6 and P21, respectively). A circulation scheme is found using an inverse model solved by singular value decomposition. Approximately 12 Sv (1 Sv=10(6) m(3) s(-1)) of C ircumpolar Deep Water that is transported northward through the Southw est Pacific Basin, mainly in the deep western boundary current, is ret urned southward at intermediate depths. The zonally integrated flow ne ar the surface is northward. The southward transport of the East Austr alian Current is estimated to be 26 Sv at 25 degrees S and 43 Sv at 32 degrees S. Assuming zero net mass transport, the derived southward he at fluxes are -0.17 +/- 0.25 PW and -0.04 +/- 0.25 PW at 17 degrees S and 32 degrees S, respectively. Thus there is an implied net loss of h eat of 0.13 PW between the two sections, equivalent to an average heat loss to the atmosphere of 6.5 +/- 5.8 W m(-2). When the net mass tran sport is assumed to be nonzero, in accordance with a westward Indonesi an Throughflow from the Pacific to the Indian Ocean, the sign of the t emperature transport changes but the meridional divergence remains ess entially the same. The vertical distribution of the assumed net mass t ransport is crucial in determining the temperature flux. In particular , when the net mass transport is assumed to be 6 Sv above 250 dbar and 4 Sv between 250 and 1000 dbar, the temperature fluxes are directed n orthward with magnitudes of 0.33 +/- 0.25 PW and 0.44 +/- 0.25 PW for the 17 degrees S and the 32 degrees S section, respectively. The fresh water fluxes suggest that there is a net evaporation of 0.39 Sv over t he region enclosed by the two sections, which is about twice as large as the climatological estimates.