The Interannual, Interdecadal Variations Of The Subduction Rate In The South Pacific And Its Effects To Tropical Pacific

Subduction rate in the South Pacific has been calculated from the assimilated ocean model data (SODA) with Huang and Qiu's equation of subduction rate (1994). The interannual and decadal variations of the subduction rate and their mechanism in the Subtropical South Pacific are analyzed. Particles Lagrangian trajectories are traced to examined the pathways from the subtropics to the tropics and propagation of anomalous signal.The results show that the three subduction areas in the Subtropical South Pacific exhibit both the interannual and decadal variations. The subduction rates in the western and central subduction areas show a interannual variations of 2~8 years and a decadal variations of around 20 years, while the subduction rate in the eastern subduction area has a interannual variability of 2~6 years and a decadal variability of 32 years. The amplitudes of the subduction rate in the western subduction area are larger than those of the central and eastern subduction areas.The subduction rate can be influenced by a number of factors such as the Ekman pumping velocity, background current field, buoyancy fluxes and wind stress curl. The annual-mean subduction rate consists of two terms: the vertical pumping term at the base of the winter mixed layer and the lateral induction term due to slope of the mixed layer base, either of which term changes would result in the variation of the subduction rate. The analysis shows that the variations of the subduction rate in both the western and central subductin areas are mainly under the control of the lateral induction term, while the subdcution rate in the eastern subduction areas are mostly affected by the lateral induction term on the interannual scale, and the change of the local wind stress curl serves to be the main factor in affecting its subduction rate on the decadal time scale.The analysis of temperature anomaly propagation and water particle tracing demonstrates that the presence of ITCZ makes most of the subduction water in the North Pacific could not reach the equator, while the main subduction water in the subtropical south pacific could reach the equatorial pacific. The temperature anomaly signal in the subduction area of the eastern Subtropical South Pacific can influence the Tropical Eastern Pacific through the ocean's internal channel and it takes about 10 years for the signal here propagate to the Equatorial regions.The creative aspects of the work are shown below. The subduction rate of every year in the South Pacifc are firstly calculated. The interannual and decadal variations of the subduction rate and their mechanism in the three main subtropical subduction areas are analyzed. the temperature anomaly signal in the subduction area are examined by particles Lagrangian trajectories.