Linkage between the dominant modes in Pacific subsurface ocean temperature and the two type ENSO events

We investigate the variations of subsurface ocean temperature (SOT) based on the monthly-Simple Ocean Data Assimilation (SODA) during 1958-2007, and discuss the linkage between the variations of SOT and the eastern and central Pacific ENSO (EP and CP-ENSO) events. The wavelet analyses suggest that the variation of the EP and CP-ENSO events shows the 2-7 and the 10-15 years oscillation in the tropical sea surface temperature (SST), and coupled with a zonal dipole mode and a tripole mode in the SOT anomalous field reveled by the singular value decomposition (SVD) analysis. During the mature phase of CP-ENSO, the positive center of SOT at the subsurface layer locates in the west of dateline, which results in the increase of SOT in the Nio4 region and causes the CP-ENSO event. Statistical analysis implies that, the eastern and central Pacific subsurface indices which are defined by the expansion coefficients of the first and third SVD mode for SOT have shown the capabilities in disguising the EP and CP-ENSO events, respectively. In addition, corresponding to the increase of the SOT amplitude on the 10-15 years time scale, we found that the frequency and intensity of CP-El Nio events has exhibited an upward trend after the 1980s, which suggests that the CP-ENSO event has shown an enhanced impact on the global climate in the past decades.