The oceanic meridional volume trans-port (MVT) in the North Subtropical Pacific is calcu-lated directly from an observed velocity field (realMVT) and indirectly from wind stress based on Sver-drup balance, respectively. It is confirmed that theSverdrup MVT is a good approximation to the realMVT for the North Subtropical Pacific except in thewestern boundary region, where the difference isexpected because of frictional and nonlinear effects.The time evolution of the MVT derived from a revisedSverdrup balance, in which a time delay due to thepropagation of the first baroclinic Rossby wave isconsidered, is well correlated with that of the realMVT on decadal time scale, especially near thewestern boundary region. It is suggested that theSverdrup balance can be used to study not only themean climatology of the oceanic circulation, but alsothe time-dependent oceanic circulation of the NorthSubtropical Pacific when the Rossby wave propaga-tion is taken into account.
The SODA data generated from a numerical model with data assimilation are used to study the de- cadal thermal anomalies in the thermocline of the South Pacific. Three notable events of decadal thermocline variations are found. First, two major warm subduction events originated from outcrop regions centered at 30°S, 150°W in the South Pacific Ocean occurred between 1960s and 1980s propagating toward the western Tropics and at 30°S, 90°W in the late 1970s propagating directly toward the eastern Tropics. Second, a special westward warm event originating from the eastern boundary around 15°S occurred in the early 1980s. Thirdly, a distinct zonal location transition of the positive temperature anomalies near 10°S took place in the late 1970s. The results suggest that the warm events in the subtropical South Pacific region are important to the decadal variability of the western tropical Pacific before the late 1970s and to the eastern tropical Pacific after the late 1970s.
