The Interannual Variation Of The Indonesian Throughflow's Response To IOD

The Indonesian Throughflow (ITF) variability is assessed using a retrospective analysis of the global ocean based on the Simple Ocean Data Aassimiation(SODA) experiment spanning the period 1958-2001 .The simulated ITF tranport is reasonable in the aspecet of different depths.Compared this the observation, the simulated seasonal cycle of the section IX1 ITF transport is fairly realistic.So it's suggested that SODA can be a reasonably accurate reconstruction of ocean circulation in the vicinity of the ITF during the available measurement record.A wavelet analysis shows that the interannual variation of the upper transport of ITF has not only an oscillation with a period of about 4-6yr ENSO cycle,but also quasi-2yr signal.It's supposed that there is some linkage between the interannual variation of the ITF and Indian Ocean dipole mode (IOD).The wavelet coherency analyses show that on the interannual scale the ITF is closely related to the surface sea temperature anomalies(SSTA) in east Indian Ocean(EIO)and IOD.On average,the variability is significant with the ITF lagging DMI by 5 months, leading EIO by 7 months.Furtherly with lag and lead correlation analysis, it's confirmed that Dipole mode in Indian Ocean is significant by leading the variation of the ITF 9 months.The variation of the ITF accompanies with the evolution of the zonal wind anomalies over tropical Indian Ocean and hence associate oceanic processes.In conclusion,tropical Indian ocean-atmosphere interaction plays an important role in the interannual variability of the ITF.The empirical orthogonal fuction(EOF) analysis of temperature anomalies in the section 115°E latitude-depth plane indicates that the leading mode of variablity has a pole character ,with strongest loading in the thermocline of northern section.It is located in the south Java current of east Indian Ocean ,so the pole is well correlated with IOD.The second eigenvector has a dipole chacracter which features positive pole in the depth 100m of north section and negetive pole confined to 150m between 15°S and 12°S.According to the Waveguide theory,the dipole is controlled by equatorial ocean dynamics forced zonal winds in the equtorial region.The negtive pole has a strong relation to the zonal wind in Pacific equatorial region evolving with ENSO,while positive pole has a relationship to the Indian zonal wind related to IOD events.Both IOD and ENSO play important roles in the interannal varibility of the ITF transport.Either pure"ENSO"or the"IOD"event has distinct effects on the ITF transport.When a positive(negetive) IOD event co-occurs during an El Nino(La Nina)year , the ITF transport anormaly tend to be less extent than pure IOD or ENSO.The IOD has competing effect on influece of ENSO.The influence of IOD and ENSO on ITF transport count the effect of each other.The IOD effects dominate in borel summer while ENSO dominates in winter or next spring.