Correlation analysis of the North Equatorial Current bifurcation and the Indonesian Throughflow

Based on monthly mean Simple Ocean Data Assimilation (SODA) products from 1958 to 2007, this study analyzes the seasonal and interannual variability of the North Equatorial Current (NEC) bifurcation latitude and the Indonesian Throughflow (ITF) volume transport. Further, Empirical Mode Decomposition (EMD) method and lag-correlation analysis are employed to reveal the relationships between the NEC bifurcation location, NEC and ITF volume transport and ENSO events. The analysis results of the seasonal variability show that the annual mean location of NEC bifurcation in upper layer occurs at 14.33°N and ITF volume transport has a maximum value in summer, a minimum value in winter and an annual mean transport of 7.75×106 m3/s. The interannual variability analysis indicates that the variability of NEC bifurcation location can be treated as a precursor of El Niño. The correlation coefficient between the two reaches the maximum of 0.53 with a time lag of 2 months. The ITF volume transport is positively related with El Niño events with a maximum coefficient of 0.60 by 3 months. The NEC bifurcation location is positively correlated with the ITF volume transport with a correlation coefficient of 0.43.